Letter to Editor
Shaheen et al. 1 recently reported a homozygous 5 bps deletion mutation
(c.1299_1303delTAAG; p.Phe433Leufs*6) in the human polo-like kinase 4
(PLK4,MIM 605031) gene and proposed that it is a compelling candidate for
primordial dwarfism (PD). Autozygosity mapping and LOD score, method of
estimating linkage distances, are adopted for the novel locus
identification. Candidate gene hunting among 144 in the r...
Letter to Editor
Shaheen et al. 1 recently reported a homozygous 5 bps deletion mutation
(c.1299_1303delTAAG; p.Phe433Leufs*6) in the human polo-like kinase 4
(PLK4,MIM 605031) gene and proposed that it is a compelling candidate for
primordial dwarfism (PD). Autozygosity mapping and LOD score, method of
estimating linkage distances, are adopted for the novel locus
identification. Candidate gene hunting among 144 in the region is based on
filtering through ToppGene suite 2. Mutation screening through Sanger
sequencing of PLK4 gene is only based on ToppGene suite ranking. In this
study authors have not mentioned how many and which samples were selected
for genotyping and linkage analysis so the predicted maximum LOD score
cannot be calculated. Maximum multipoint LOD score (2.5) obtained by the
authors is quite lower than the established threshold values (3.0). In
article it has been stated that all PD genes in training set in comparison
to all 144 genes of the locus in test set were enrolled in ToppGene
candidate prioritization. These genes lists must be provided along with
test parameters. In our opinion these informations are essential for data
reproducibility and validation.
Only PLK4 gene has been selected for Sanger sequencing but The candidate
region (Chr4:112904466-129392060, GRCh37/hg19) includes some of the well-
known syndromes characterized by autosomal recessive intellectual
disabilities, microcephaly, short stature, and overlapping phenotypes.
Alazami syndrome caused by mutations in LARP7, autosomal recessive type 1
mental retardation caused by mutations in PRSS12, Bardet-Biedl syndrome
caused by mutations in BBS7 and BBS12, Van Maldergem syndrome 2 caused by
mutations in FAT4, neuronal ceroid lipofuscinosis 7 caused by mutations in
MFSD8, a multisystem disorder including brain function caused by mutation
in SCLT1, as well as genes involved in mitosis and brain development e.g.
MAD2L1, FGF2, INTU, have not been discussed throughout the manuscript.
Furthermore, chromatograms for obligate carriers have not been presented
nor the Saudi population screening for minor allele frequency has been
performed. Similarly a homozygous variant (NM_014264.4, c.1556G>C;
p.Trp519Ser) reported in ESP6500 (http://evs.gs.washington.edu/EVS/)
alters a highly conserved amino acid of PLK4 however it has not been
assigned to any of primordial dwarfism phenotype and not discussed by the
authors. In fact, phenotypic overlaps among the study mutants and the
above syndromes would be of far more value instead of paying an
exaggerated attention to PLK4 biology.
References
1 Shaheen R, Al Tala S, Almoisheer A et al. Mutation in PLK4,
encoding a master regulator of centriole formation, defines a novel locus
for primordial dwarfism. Journal of medical genetics 2014.
2 Chen J, Bardes EE, Aronow BJ et al. ToppGene Suite for gene list
enrichment analysis and candidate gene prioritization. Nucleic acids
research 2009; 37: W305-11.
I have read all the respective article and I agreed to most of the
findings. Recently, our group has been working with metabolomics towards
lipodystropy and we did found similar findings. Recently it has been
reported (Abael et al., 2010) that the changes in local thyroid hormone
(TH) metabolism may occur in areas with lipoatrophy. These changes could
be because of different molecular mechanisms (for example; levels of...
I have read all the respective article and I agreed to most of the
findings. Recently, our group has been working with metabolomics towards
lipodystropy and we did found similar findings. Recently it has been
reported (Abael et al., 2010) that the changes in local thyroid hormone
(TH) metabolism may occur in areas with lipoatrophy. These changes could
be because of different molecular mechanisms (for example; levels of
monocarboxylate transporter 8 and iodothyronine deiodinases). Recently, it
has been reported that the prelamin A accumulating mesenchymal stem cells
(hMSCs) have a premature aging phenotype which affects their functional
competence in vivo. The combination of prelamin A accumulation and stress
conditions enhance the aging phenotype by dysregulating the activity of
the octamer binding protein Oct-1(Infante et al., 2014). There is a need
to evaluate Oct-1 in type 2 familial partial lipodystrophy. Stress could
be in the form of hypoxia and oxygen concentration and PO2 is documented
to be involved in the activity of nucleoside reverse transcriptase
inhibitors (NRTIs) to characterised the metabolic effect on the targeted
adipose tissues (Gentil et al., 2006). There could be a relation between
hypoxia inducible factors (HIF1 & HIF2) to be defined for
lipodystrophy.
Hypoxia Inducible Factor 1 (HIF-1) was firstly identified to be a
nuclear factor involved in activation of gene expression under the
response of reduced cellular O2 during Erythropoietin expression and
regulation (Semenza & Wang, 1992). Following this invention, HIF-1 was
reported to be involved in expression and regulation of Vascular
Endothelial Growth Factor (VEGF), glycolytic enzymes, nitric oxide
synthetase and glucose transporter 1 (Glut 1) (Wenger & Gassmann.
1997; Semenza, 1998). Structurally, HIF-1 is a heterodimer composed of two
basic helix-loop-helix PAS domains (bHLH-PAS) protein, called HIF-1? and
HIF-1? subunits (Wang et al., 1995).
Tian and colleagues (Tian et al., 1997) identified a novel bHLH-PAS
protein called Endothelial PAS domain protein (EPAS1) with 48% sequence
similarity with HIF-1 ?. Further studies termed it as HIF-like factor
(HLF) (Ema et al., 1997) followed by HIF-related factor (HRF) (Flamme et
al., 1997) followed by current name given to this factor to be HIF-2
(Wenger & Gassmann, 1997). Recently, it has been shown that HIF-2 ?
forms a functional heterodimer with HIF-1?, resulting in the HIF-2 complex
and this complex has been found to bind the same hypoxia response element
(HRE) of Epo and VEGF gene to which HIF-1 complex binds. Both of these HRE
and bindings (binding of HIF-1 and HIF-2 complex) are activated under
hypoxic conditions (Tian et al., 1997, Ema et al., 1997).
The role of HIF-2 as compared to HIF-1 has been much less studied.
Patel and colleagues (Patel et al., 2008) reported HIF-2 complex to be
more tissue specific than HIF-1 by suggesting its response to different
levels of O2 and this justified strongly the role of HIF-2 on expression
of genes in obesity and inflammation. Hyperplasia and hypertrophy in
adipocytes can lead to many morphological and molecular changes in
adipocytes resulting in hypoxia, metabolic dysregulation and increased
expression and secretion of cytokines (Hosogai et al., 2007, Ye et al.,
2007). Different vital genes involved in metabolic and diet induced
obesity have been reported to be expressed under the action of HIF-1.
Recently, NF-KB has been reported to be induced through hypoxia (Culver et
al., 2010). It has been suggested that the role of HIF-2 and NF-?B can be
considered because of a strong evidence of former (HIF-2) been reported to
be linked with hypoxia inducible inhibition of insulin signaling
(Regazzetti et al., 2009). There is a strong evidence of hypoxia in
obesity (Ye et al., 1997), with a reported finding of HIF-2 to be tissue
specific rather than HIF-1 (Patel et al., 2008).
The potential role of HIF-2 and NF-KB in pathways involving vital
genes and proteins in response of adipocytes to hypoxia needs to be
explored at molecular level to get a better picture and role of hypoxia in
inducing obesity genes expression in this respective report beside
inflammation as per induced.
References:
Culver C, Sundqvist A, Mudie S, Melvin A, Xirodimas D, Rocha S.
Mechanism of hypoxia-induced NF-kappaB. Mol Cell Biol. 2010
Oct;30(20):4901-21. doi: 10.1128/MCB.00409-10.
Ema M, Taya S, Yokotani N, Sogawa K, Matsuda Y, and Fujii-Kuriyama Y
(1997) A novel bHLH-PAS factor with close sequence similarity to hypoxia-
inducible factor 1alpha regulates the VEGF expression and is potentially
involved in lung and vascular development. Proc Natl Acad Sci USA 94: 4273
-4278.
Gentil C, Le Jan S, Philippe J, Leibowitch J, Sonigo P, Germain S,
Pi?tri-Rouxel F. Is oxygen a key factor in the lipodystrophy phenotype?
Lipids Health Dis. 2006 Oct 18;5:27.
Hosogai, N., Fukuhara, A., Oshima, K., Miyata, Y., Tanaka, S.,
Segawa, K., Furukawa, S., Tochino, Y., Komuro, R., Matsuda, M., and
Shimomura, I. (2007) Adipose tissue hypoxia in obesity and its impact on
adipocytokine dysregulation. Diabetes 56, 901-911.
Infante A, Gago A, de Eguino GR, Calvo-Fern?ndez T, G?mez-Vallejo V,
Llop J, Schlangen K, Fullaondo A, Aransay AM, Mart?n A, Rodr?guez CI.
Prelamin A accumulation and stress conditions induce impaired Oct-1
activity and autophagy in prematurely aged human mesenchymal stem cell.
Aging (Albany NY). 2014 Apr;6(4):264-80.
Lado-Abeal J, Calvo RM, Victoria B, Castro I, Obregon MJ, Araujo-
Vilar D.Regional decrease of subcutaneous adipose tissue in patients with
type 2 familial partial lipodystrophy is associated with changes in
thyroid hormone metabolism. Thyroid. 2010 Apr;20(4):419-24. doi:
10.1089/thy.2009.0267.
Patel SA, Simon MC. Biology of hypoxia-inducible factor-2alpha in
development and disease. Cell Death Differ. 2008 Apr;15(4):628-34. doi:
10.1038/cdd.2008.17. Epub 2008 Feb 15. Review. PubMed PMID: 18259197;
PubMed Central PMCID:PMC2882207.
Regazzetti C, Peraldi P, Gr?meaux T, Najem-Lendom R, Ben-Sahra I,
Cormont M, Bost F, Le Marchand-Brustel Y, Tanti JF, Giorgetti-Peraldi S.
Hypoxia decreases insulin signaling pathways in adipocytes. Diabetes. 2009
Jan;58(1):95-103. doi: 10.2337/db08-0457.
Tian H, McKnight SL, and Russell DW (1997) Endothelial PAS domain
protein 1 (EPAS1), a transcription factor selectively expressed in
endothelial cells. Genes Dev 11: 72-82.
Semenza, G. L. and Wang, G. L. (1992). A nuclear factor induced by
hypoxia via de novo protein synthesis binds to the human erythropoietin
gene enhancer at a site required for transcriptional activation. Molec.
cell. Biol. 12, 5447-5454.
Semenza, G. L. (1998). Hypoxia-inducible factor 1: master regulator
of O2 homeostasis. Curr. Opin. Genet. Dev. 8, 588-594.
Wang, G.L., Jiang, B.H., Rue, E.A., Semenza, G.L., 1995.
Hypoxia?inducible factor?1 is a basic? helix?loop?helix?pas heterodimer
regulated by cellular O2 tension. Proc Natl Acad Sci USA 92, 5510?5514.
Wenger, R. H. and Gassmann, M. (1997). Oxygen(es) and the hypoxia-
inducible factor-1. Biol. Chem. 378, 609-616.
Ye, J., Gao, Z., Yin, J., and He, Q. (2007) Hypoxia is a potential
risk factor for chronic inflammation and adiponectin reduction in adipose
tissue of ob/ob and dietary obese mice. Am J Physiol Endocrinol Metab 293,
E1118-1128.
C-terminus truncation of Seipin as a good potential sign of diseases
Wei-Li Yu and Yun Sun
Seipin is a transmembrane protein of the endoplasmic reticulum with N, C-terminus residing the intracytoplasmic side.1 2 Loss of Seipin function has been shown to lead to severe lipodystrophy, motor neuropathy and silver syndrome.3 However, its molecular mechanism is still unknown. Recently Guillén-Navarro E et al 4...
C-terminus truncation of Seipin as a good potential sign of diseases
Wei-Li Yu and Yun Sun
Seipin is a transmembrane protein of the endoplasmic reticulum with N, C-terminus residing the intracytoplasmic side.1 2 Loss of Seipin function has been shown to lead to severe lipodystrophy, motor neuropathy and silver syndrome.3 However, its molecular mechanism is still unknown. Recently Guillén-Navarro E et al 4 indicated that complete skipping of exon 7 was associated with a new neurodegenerative syndrome. The mutation caused early termination, resulting in C-terminally truncated proteins p.Tyr289LeufsX64. It demonstrated that C-terminus of Seipin played a key role in the pathogenesis of this new neurological disease. This result suggests that C-terminus truncation of Seipin might be a good potential prediction of this disease.
Other studies have been carried with the similar aim. Van Maldergem et al 5 had reported that C-terminus deficiency of Seipin due to kipping of exon 7 caused a case of severe psychomotor delay and pyramidal signs. These mutations were associated with intellectual impairment. Furthermore, Yang W et al 6 found that C-terminus truncated proteins such as R275X and Q391X, led to lipodystrophy. It indicated that C-terminus of Seipin could regulate lipogenesis and adipogenesis. In addition, Yang W et al 7 identified that C-terminus of Seipin interacted with 14-3-3β, which patiotemporally recruited an interacting partner of actin-severing protein cofilin-1 during adipocyte differentiation. They proposed that C-terminus of Seipin might regulate adipogenesis by recruiting cofilin-1 to remodel actin cytoskeleton through the 14-3-3β protein.
These findings suggest that C-terminus truncation of Seipin may be a potential sign of diseases such as lipodystrophy, psychomotor delay and neurological diseases. We greatly enjoyed reading the article by Guillén-Navarro E et al and believe C-terminus truncation of Seipin may be useful for prediction of diseases.
The authors declare no conflict of interest.
1. Magré J, Delépine M, Khallouf E, Gedde-Dahl T Jr, Van Maldergem L, Sobel E, Papp J, Meier M, Mégarbané A, Bachy A, Verloes A, d’Abronzo FH, Seemanova E, Assan R, Baudic N, Bourut C, Czernichow P, Huet F, Grigorescu F, de Kerdanet M, Lacombe D, Labrune P, Lanza M, Loret H, Matsuda F, Navarro J, Nivelon-Chevalier A, Polak M, Robert JJ, Tric P, Tubiana-Rufi N, Vigouroux C, Weissenbach J, Savasta S, Maassen JA, Trygstad O, Bogalho P, Freitas P, Medina JL, Bonnicci F, Joffe BI, Loyson G, Panz VR, Raal FJ, O’Rahilly S, Stephenson T, Kahn CR, Lathrop M, Capeau J; BSCL Working Group. Identification of the gene altered in Berardinelli-Seip congenital lipodystrophy on chromosome 11q13. Nat Genet 2001; 28: 365-70.
2. Lundin C, Nordstrom R, Wagner K, Windpassinger C, Andersson H, von Heijne G and Nilsson I. Membrane topology of the human seipin protein. FEBS Lett 2006; 580: 2281-2284.
3. Chen W, Yechoor VK, Chang BH, Li MV, March KL, Chan L. The human lipodystrophy gene product Berardinelli-Seip congenital lipodystrophy 2/seipin plays a key role in adipocyte differentiation. Endocrinology 2009; 150:4552-4561.
4. Encarna Guillén-Navarro, Sofía Sánchez-Iglesias, Rosario Domingo-Jiménez, Berta Victoria, Alejandro Ruiz-Riquelme, Alberto Rábano, Lourdes Loidi, Andrés Beiras, Blanca González-Méndez, Adriana Ramos, Vanesa López-González, María Juliana Ballesta-Martínez, Miguel Garrido-Pumar, Pablo Aguiar, Alvaro Ruibal, Jesús R Requena, and David Araújo-Vilar. A new seipin-associated neurodegenerative syndrome. J Med Genet 2013; 50:401-409.
5. Van Maldergem L, Magré J, Khallouf TE, Gedde-Dahl T Jr, Delépine M, Trygstad O, Seemanova E, Stephenson T, Albott CS, Bonnici F, Panz VR, Medina JL, Bogalho P, Huet F, Savasta S, Verloes A, Robert JJ, Loret H, De Kerdanet M, Tubiana-Rufi N, Mégarbané A, Maassen J, Polak M, Lacombe D, Kahn CR, Silveira EL, D’Abronzo FH, Grigorescu F, Lathrop M, Capeau J, O’Rahilly S. Genotype-phenotype relationships in Berardinelli-Seip congenital lipodystrophy. J Med Genet 2002; 39: 722-33.
6. Yang W, Thein S, Guo X, Xu F, Venkatesh B, Sugii S, Radda GK and Han W. Seipin differentially regulates lipogenesis and adipogenesis through a conserved core sequence and an evolutionarily acquired C-terminus. Biochem J 2013; 452: 37-44.
7. Yang W, Thein S, Wang X, Bi X, Ericksen RE, Xu F, Han W. BSCL2/seipin regulates adipogenesis through actin cytoskeleton remodeling. Human Molecular Genetics 2014; 23: 502-513.
We found this paper to be immensely informative while researching
junctional epidermolysis bullosa (JEB) for a particular clinical case,
which is described below. During the course of testing for this
particular case we found evidence suggesting that that the D982G mutation
in LAMB3 may not be disease-causing.
In their paper, Varki, Sadowski, and Pfender et al. present the case
of an eight-month-old male patie...
We found this paper to be immensely informative while researching
junctional epidermolysis bullosa (JEB) for a particular clinical case,
which is described below. During the course of testing for this
particular case we found evidence suggesting that that the D982G mutation
in LAMB3 may not be disease-causing.
In their paper, Varki, Sadowski, and Pfender et al. present the case
of an eight-month-old male patient who presented with mild blistering of
the legs and feet at birth but who exhibited no further blistering.
Mutation analysis for this boy reportedly revealed two LAMB3 missense
mutations, R366W and D982G. It is not noted if phase of these mutations
is known. The author suggested that the abnormal proteins arising from
these alleles are able to function in the postnatal period, thus leading
to spontaneous amelioration of the phenotype after birth.
Here we present the case of an unaffected parent of a child affected
with Herlitz-JEB (H-JEB) who himself is a compound heterozygote for two
LAMB3 mutations, D982G and 31dupC.
In our case, the second child born to a non-consanguineous Caucasian
couple with no family history of JEB was noted to have open sores soon
after birth. He was diagnosed with H-JEB based on the results of skin
biopsy, and he died at five weeks of age. Molecular genetic testing
identified two LAMB3 premature termination mutations, 31dupC (paternally
inherited) and R635X (maternally inherited). His unaffected father was
also found to carry the D982G mutation.
The 31insC and R635X mutations in LAMB3 have been described in
multiple individuals with H-JEB. To the best of our knowledge, the D982G
missense mutation in LAMB3 has been described only in this paper. Our
finding of this same missense mutation in trans with a more severe LAMB3
mutation in a reportedly completely unaffected individual argues against
D982G being a disease-causing mutation. In addition, this mutation is
predicted to be benign by Polyphen-2.
The findings in our case argue against D982G being a disease-causing
mutation, as had been suggested in this paper. However, the possibility
of reduced penetrance cannot be excluded at this time.
RSS was first described in 1953 [1]. It is a clinically and
genetically heterogeneous condition. Clinical diagnosis is based on
various characteristics including slow growth before and after birth,
relative macrocephaly, a prominent forehead at a young age,
hemihypotrophy, and fifth finger clinodactyly. Five different diagnostic
scoring systems of RSS have been published. These systems take into
account most major clini...
RSS was first described in 1953 [1]. It is a clinically and
genetically heterogeneous condition. Clinical diagnosis is based on
various characteristics including slow growth before and after birth,
relative macrocephaly, a prominent forehead at a young age,
hemihypotrophy, and fifth finger clinodactyly. Five different diagnostic
scoring systems of RSS have been published. These systems take into
account most major clinical features and sometimes minor clinical
features, and are on the whole quite similar. These five scoring systems
were recently compared in the Journal of Medical Genetics in terms of
sensitivity, specificity, and positive or negative predictive value [2].
In this evaluation, the scoring system described by Netchine et al. [3]
showed a high degree of specificity and sensitivity. This scoring system
has also been used by other teams from various countries in the diagnosis
of RSS (see for instance [4]). Furthermore, the article describing this
scoring system [3] was reviewed by the editorial board of The Journal of
Clinical Endocrinology & Metabolism (JCEM) and received an award in
2008 from the Endocrine Society. This article has been cited in PUBMED 128
times.
The first described molecular abnormality in RSS was the maternal
uniparental disomy of chromosome 7 (mUPD7). This defect is present in 5-
10% of individuals affected by RSS [5, 6]. This observation suggests the
aberrant dosage of imprinted genes may be involved in the pathology of
RSS, although the gene(s) involved remain unknown. Recently, abnormalities
of 11p15, a locus also harboring imprinted genes, have been described.
This region contains two separate imprinting clusters: the telomeric
domain (ICR1) that regulates H19 and IGF2, and the centromeric domain
(ICR2) that regulates the long non-coding RNA KCNQ1OT1 and CDKN1C genes.
Of note, cytogenetic, genetic, and epigenetic disturbances of the 11p15
region encompassing ICR1 and ICR2 are associated with the overgrowth
disorder Beckwith Wiedemann syndrome (BWS). BWS is a clinical and
molecular mirror of RSS, and around 8% of cases involve loss of function
mutations of CDKN1C [7]. In RSS, loss of methylation (LOM) of the paternal
ICR1 is the most prevalent defect. This epigenetic change is found in up
to 60% of RSS patients [3, 8], although it has been reported to occur less
frequently in some populations (e.g. with a frequency of ~31% in Japanese
patients) [4]. Approximately 30% of RSS patients are ? idiopathic ? with
no molecular anomaly yet identified.
General comments on the items of the scoring system described in [3]:
Young children with RSS have a very different clinical profile than older
children or adults with RSS. Feeding difficulties are much more pronounced
in early life and therefore have to be assessed at a young age. Older
children and adults may become overweight. Feeding difficulties can be
difficult to assess; therefore, one of the conclusions of our paper in
2007 was to replace the item ? feeding difficulties ? with ? feeding
difficulties and /or a BMI two SDs below the mean at around two years of
age ?. The prominent forehead is distinct from relative macrocephaly.
Indeed, relative macrocephaly is characterized by a growth restriction
affecting mostly the body, whereas circumference of the head is relatively
less unaffected. A prominent forehead however, is a dysmorphic feature
that describes the characteristic shape of these patients' forehead
protruding over the plane of the face. This feature tends to disappear in
late childhood and therefore has to be assessed around two years of age.
Body asymmetry is a feature of RSS, but is not present in all RSS
patients. This feature is more frequent in RSS patients with epigenetic
changes to 11p15 than in patients with mUPD7. For example, in our sample
of 145 RSS patients with 11p15 LOM, 79% of patients had hemihypotrophy,
whereas in a sample of 16 RSS patients with mUPD7, none of the patients
were affected by hemihypotrophy (p<0.0001). This is probably due to the
fact that the 11p15 LOM occurs in a mosaic manner, such that the
proportion of cells that possess this epigenetic change may differ between
the left and right side of the body. The item post natal growth
retardation also has to be assessed around two years of age. This is
because most RSS patients are treated with growth hormone generally
starting between two and four years of age, to improve their growth rate.
Bone age and pubertal status also has to be taken into account when
analyzing the growth of a child affected by RSS. Indeed, these children
frequently have an advanced bone age due to aggressive adrenarche and
early puberty. Thus, even though their height may be normal during
childhood, their final height may be lower than average due to premature
bone fusion.
Specific comments in response to this letter
The diagnosis of RSS in the patients reported by Brioude et al. is not
questionable because all the patients carrying the mutation fulfilled the
clinical criteria of RSS as described by Netchine et al. in 2007.
Furthermore, these patients also fulfill the RSS clinical criteria
according to other validated RSS clinical scoring systems such as the
Birmingham scoring system [2]. However, as mentioned above, the clinical
diagnosis of RSS is often difficult. RSS scoring systems are helpful to
orient the diagnosis; nonetheless, it is also very important that an
experienced clinical geneticist or pediatrician make this diagnosis. The
pediatrician (IO) who referred this family to our laboratory has a lot of
clinical experience in RSS and has followed two generations of this family
(second and third). The pediatrician (IO) became convinced of the
diagnosis of a very rare case of familial RSS when the third generation of
this family came to the clinic for consultation.
In the clinical scoring system described by Netchine et al. [3], body
asymmetry is one of the six criteria for the clinical diagnosis of RSS.
However, in a family carrying a CDKN1C mutation, body asymmetry is not
expected to occur because the molecular defect is present in all the cells
of the body (unlike the mosaic epigenetic change at the 11p15 locus). This
hypothesis is in accordance with the observation that patients with
Beckwith Wiedemann syndrome who carry CDKN1C loss of function mutations
are not usually affected by body asymmetry [7]. Similarly, patients with
IMAGe syndrome with a mutation in CDKN1C do not have body asymmetry [9].
Thus, the absence of body asymmetry does not exclude the diagnosis of RSS
in this particular case. Furthermore, we found that RSS patients with
mUPD7 do not show body asymmetry, and some RSS patients with 11p15 LOM are
also unaffected (20% in our sample of patients).
As mentioned above, all the patients described here had feeding
difficulties and/or a BMI two SDs below the mean at around two years of
age. We can consider a low BMI to be equivalent to feeding difficulties,
as mentioned in the legend of table 2 and proposed in our paper in 2007
[3].
Relative macrocephaly was not present at birth for all the patients
presented here (notably in the propositus IV.1). However, this trait was
present at two years of age in all patients carrying the mutation.
Therefore, this characteristic may help to distinguish RSS patients with a
mutation in CDKN1C from patients with 11p15 LOM. However, the absence of
relative macrocephaly is not enough to preclude the clinical diagnosis of
RSS in these patients. Although the triangular face does not appear to be
obvious in the pictures of the patients, this feature has been confirmed
by the patients' physician (IO). Furthermore, this trait (triangular face
and prominent forehead) is usually less obvious in adult patients.
Besides, a triangular face is not a clinical criterion for RSS diagnosis
and is not part of our scoring system.
All the patients described here presented growth retardation: Length at
birth and then height and/or weight was two SDs below the mean according
to French reference charts both at birth and after birth. All the
patients with the CDKN1C mutation did not attain a normal height at the
age of 2 years. Patient III.7 received a long-term therapy consisting of
growth hormones and Triptorelin acetate and thus reached a final height of
157 cm. However this patient's sister, (patient III.6) received growth
hormone therapy for a shorter duration than her sister resulting in a
lower final height. Today, most RSS patients are treated with growth
hormones and the best improvement in final height is attained when the
rapid advancement in bone age is also treated.
Individuals II.4 and III.10 do not carry the CDKN1C mutation, and cannot
be considered as having RSS because they do not present the clinical
criteria as described above. These two individuals did not show relative
macrocephaly at birth or at the age of two years. Their size at birth was
either normal (II.4), or, in the case of III.10, small, but nonetheless
larger than new-born babies corresponding to family members who carry the
mutations. Individuals II.4 and III.10 had a normal BMI, and II.4 had a
normal adult height without any therapy. We agree with the point that
individual III.10 showed a short final height despite growth hormone
therapy. This patient was followed like the other patients with short
stature of this family by the same pediatrician (IO), who did not
clinically assess her as having RSS. To date, the causal mechanism of her
short adult height has not been elucidated.
CONCLUSION
Defining the clinical criteria of a clinically and molecularly
heterogeneous syndrome like RSS is not straightforward. Nonetheless, we
are convinced that the family described here, represents a rare case of
familial RSS. The diagnosis of RSS was made by a physician experienced in
RSS who had the opportunity to follow and treat two generations of this
exceptional family. The scoring system described by Netchine et al. [3],
but also other RSS scoring systems such as those evaluated by Dias et al.
[2] also favor this diagnosis. The absence of body asymmetry does not
rule out the diagnosis of RSS, as in mUPD7 RSS cases or in 20% of 11p15
LOM cases. In this case, the absence of body asymmetry is consistent
with the genetic cause identified. This CDKN1C mutation is therefore a new
genetic cause of familial RSS.
The CDKN1C mutation identified in this RSS familial case affects the same
amino acid as a mutation described by Arboleda et al. [9] in patients
with IMAGe syndrome. This observation will be of great interest for the
readers of The Journal of Medical Genetics. IMAGe syndrome has some
similarities with RSS, including fetal and postnatal growth retardation
and a prominent forehead, but is also typically characterized by bone
anomalies and a severe adrenal insufficiency that were not present in
this family. It is striking to note that a mutation on the exact same
amino acid, but with a different substitution, can lead to severe adrenal
insufficiency in one case and a normal adrenal function in the other case,
and therefore to two distinct syndromes.
As of 2013, 60 years after the first description of RSS, several molecular
causes of RSS have been identified (mUPD7 and various types of 11p15
anomalies) accounting for about 70% of etiologies. We suggest that CDKN1C
mutations are a new molecular cause of familial RSS. Given the clinical
and molecular heterogeneity of RSS we suggest that RSS should no longer be
considered as a syndrome but as a spectrum of disorders with a variety of
causes. This would make it easier to understand why RSS is clinically and
molecularly heterogeneous. However, it is important for RSS patients to be
identified as belonging to a same spectrum and not to multiple categories
of very rare conditions, because these patients share a lot of clinical
manifestations and have similar treatment needs. This will allow the
development of common clinical guidelines for these patients, and well
help in the implementation of clinical trials that are always difficult
to establish for rare diseases. The identification of exact genetic defect
is also a cornerstone for an accurate genetic counseling.
1 Silver HK, Kiyasu W, George J, Deamer WC. Syndrome of congenital
hemihypertrophy, shortness of stature, and elevated urinary gonadotropins.
Pediatrics 1953;12(4):368-76.
2 Dias RP, Nightingale P, Hardy C, Kirby G, Tee L, Price S, Macdonald F,
Barrett TG, Maher ER. Comparison of the clinical scoring systems in Silver
-Russell syndrome and development of modified diagnostic criteria to guide
molecular genetic testing. J Med Genet 2013;50(9):635-9.
3 Netchine I, Rossignol S, Dufourg MN, Azzi S, Rousseau A, Perin L, Houang
M, Steunou V, Esteva B, Thibaud N, Demay MC, Danton F, Petriczko E,
Bertrand AM, Heinrichs C, Carel JC, Loeuille GA, Pinto G, Jacquemont ML,
Gicquel C, Cabrol S, Le Bouc Y. 11p15 imprinting center region 1 loss of
methylation is a common and specific cause of typical Russell-Silver
syndrome: clinical scoring system and epigenetic-phenotypic correlations.
J Clin Endocrinol Metab 2007;92(8):3148-54.
4 Fuke T, Mizuno S, Nagai T, Hasegawa T, Horikawa R, Miyoshi Y, Muroya K,
Kondoh T, Numakura C, Sato S, Nakabayashi K, Tayama C, Hata K, Sano S,
Matsubara K, Kagami M, Yamazawa K, Ogata T. Molecular and clinical studies
in 138 Japanese patients with Silver-Russell syndrome. PLoS One
2013;8(3):e60105.
5 Kotzot D, Schmitt S, Bernasconi F, Robinson WP, Lurie IW, Ilyina H,
Mehes K, Hamel BC, Otten BJ, Hergersberg M, et al. Uniparental disomy 7 in
Silver-Russell syndrome and primordial growth retardation. Hum Mol Genet
1995;4(4):583-7.
6 Preece MA, Price SM, Davies V, Clough L, Stanier P, Trembath RC, Moore
GE. Maternal uniparental disomy 7 in Silver-Russell syndrome. J Med Genet
1997;34(1):6-9.
7 Brioude F, Lacoste A, Netchine I, Vazquez MP, Auber F, Audry G, Gauthier
-Villars M, Brugieres L, Gicquel C, Le Bouc Y, Rossignol S. Beckwith-
Wiedemann Syndrome: Growth Pattern and Tumor Risk according to Molecular
Mechanism, and Guidelines for Tumor Surveillance. Horm Res Paediatr
2013;80:457-65.
8 Gicquel C, Rossignol S, Cabrol S, Houang M, Steunou V, Barbu V, Danton
F, Thibaud N, Le Merrer M, Burglen L, Bertrand AM, Netchine I, Le Bouc Y.
Epimutation of the telomeric imprinting center region on chromosome 11p15
in Silver-Russell syndrome. Nat Genet 2005;37(9):1003-7.
9 Arboleda VA, Lee H, Parnaik R, Fleming A, Banerjee A, Ferraz-de-Souza B,
Delot EC, Rodriguez-Fernandez IA, Braslavsky D, Bergada I, Dell'angelica
EC, Nelson SF, Martinez-Agosto JA, Achermann JC, Vilain E. Mutations in
the PCNA-binding domain of CDKN1C cause IMAGe syndrome. Nat Genet
2012;44(7):788-92.
In 2007, Netchine et al. identified imprinting center region I (ICRI)
loss of methylation (LOM) as a cause of typical Russell Silver syndrome
(RSS) in 37 of 58 subjects who met their recruitment criteria of
intrauterine growth retardation (IUGR/SGA) plus at least 3 of 5 criteria:
1) postnatal growth retardation; 2) relative macrocephaly at birth; 3)
prominent forehead during early childhood; 4) body asymmetry, and; 5)
fe...
In 2007, Netchine et al. identified imprinting center region I (ICRI)
loss of methylation (LOM) as a cause of typical Russell Silver syndrome
(RSS) in 37 of 58 subjects who met their recruitment criteria of
intrauterine growth retardation (IUGR/SGA) plus at least 3 of 5 criteria:
1) postnatal growth retardation; 2) relative macrocephaly at birth; 3)
prominent forehead during early childhood; 4) body asymmetry, and; 5)
feeding difficulties during early childhood. It is noteworthy that all 25
of the individuals with LOM met at least 4 of these criteria versus 36% of
the 12 without the defect. Case definition is problematic for a
heterogeneous condition such as RSS without such a demonstrated
abnormality.
While the diagnosis of RSS in the subjects with ICR1 LOM and at least
4 of the 5 criteria beyond SGA is credible, applying a less stringent
definition to the family with CDKN1C mutation recently reported in Journal
of Medical Genetics (2013;50:823-830) may not be justifiable. In the first
place, relative macrocephaly and prominent forehead during early childhood
are really a single abnormality. Nonetheless, accepting the authors'
criteria, the validity of which is self citation to the 2007 paper, only
one of the 6 affected individuals had feeding difficulties, and none had
body asymmetry, the most specific to RSS of the authors' criteria.
Patient IV-1, the proband, is said in the table to have 4 of 5 RSS
criteria but her head circumference SDS at birth was consistent with her
length SDS. Thus the only authors' criterion she met beyond IUGR was
prominent forehead during early childhood and possible postnatal growth
retardation; however, she went from a birth length SDS of -4.1 to a two-
year height SDS of -3.0. Though she was said to have triangular facies,
not a criterion, the photo is less than convincing. Her mother, III-6 was
described as having 3 of the 5 RSS criteria, 2 of which are the related
relative macrocephaly and prominent forehead and the third, postnatal
growth failure. She is said to have triangular facies which is not
supported by the photograph.
The aunt of the proband, III-7, with an adult height SDS of -1.1 from
a birth length of -4.6 SDS and -2.7 at age 2 is obviously not an example
of postnatal growth failure; neither is her head circumference at birth (-
4.2 SDS) indicative of relative macrocephaly, although the measurement at
2 years of age is consistent with relative macrocephaly, but this is not
the criterion. She is also said to have prominent forehead and triangular
face, the latter refuted by the photograph. The claim that she met 4 of
the 5 criteria cannot be justified.
Another aunt III-4 is also claimed to meet 4 of the 5 criteria with
relative macrocephaly at birth, prominent forehead, failure of catch up
growth, and feeding difficulties during infancy. She did, however, improve
from a birth length SDS of -4.2 to a 2 year height SDS of -3 and no adult
height is given. The proband's grandmother II-1, was said to be SGA, but
no figures are given for birth or subsequent auxology except adult height
of -3.3 SDS.
Finally, aunt III-10 with IUGR does not carry the mutation in CDKN1C,
but her adult height is the same as her affected cousin III-6 and
comparable to those of her affected aunts II-1 and II-2.
In sum, these authors have described 6 females in 3 generations of a
family having IUGR with inconsistent postnatal growth failure and
relatively normal head size, of whom 5 have a maternally transmitted
CDKN1C mutation and one is unexplained. The phenotype is not sufficiently
specific for classification as RSS.
Re: Disruption of RAB40AL function leads to Martin-Probst syndrome, a
rare X-linked multisystem neurodevelopmental human disorder. Bedoyan JK,
Schaibley VM, Peng W, Bai Y, Mondal K, Shetty AC, Durham M, Micucci JA,
Dhiraaj A, Skidmore JM, Kaplan JB, Skinner C, Schwartz CE, Antonellis A,
Zwick ME, Cavalcoli JD, Li JZ, Martin DM. J Med Genet. 2012 May;49(5):332-
40.
With great interest we have read the article by B...
Re: Disruption of RAB40AL function leads to Martin-Probst syndrome, a
rare X-linked multisystem neurodevelopmental human disorder. Bedoyan JK,
Schaibley VM, Peng W, Bai Y, Mondal K, Shetty AC, Durham M, Micucci JA,
Dhiraaj A, Skidmore JM, Kaplan JB, Skinner C, Schwartz CE, Antonellis A,
Zwick ME, Cavalcoli JD, Li JZ, Martin DM. J Med Genet. 2012 May;49(5):332-
40.
With great interest we have read the article by Bedoyan and
colleagues. The authors state that disruption of RAB40AL function by a
dinucleotide missense change (chrX:102,079,078-102,079,079AC?GA p.D59G;
hg18) causes Martin-Probst syndrome, a rare X-linked disorder
characterised by deafness, cognitive impairment, short stature and
distinct craniofacial dysmorphisms, among other clinical features.
However, we have reasons to question that conclusion.
We have identified the same dinucleotide missense change in four out
of 446 index patients from families with X-linked intellectual disability
(XLID) by performing high-throughput sequencing of all X chromosome-
specific exons. However, one patient in whom we had identified the p.D59G
substitution also carried a deletion on chromosome 14 that unequivocally
explained the clinical phenotype, which led us to speculate that in this
family the RAB40AL change may not be causative of the phenotype.
Therefore, we carried out segregation analysis in the remaining three
families. One family was not informative for the RAB40L change. In this
family both the clinical phenotype and segregation analyses of
additionally identified variants suggested that this family more likely
carries a pathogenic mutation in another XLID gene. In the remaining two
families, Sanger sequencing confirmed the RAB40AL p.D59G substitution in
the index patients. However, in each of these families, one of the
affected male sibs did not carry the p.D59G substitution. Conversely, the
exome variant server (ESP6500) and dbSNP database report two normal males
who are hemizygous for the p.D59G substitution (dbSNP134 rs145606134). In
yet another XLID family, we have observed a frameshift mutation
(chrX:102192671-102192672 [hg19], ins1bp, p.A143GfsX12) in RAB40AL. In
this family, in a healthy hemizygous male as well as several healthy
homozygous females carried the frameshift variant.
Taken together, these data seem to indicate that the RAB40AL variants
observed are not related to the XLID in our families. Moreover, they
suggest that the RAB40AL p.D59G substitution may not be the cause of
Martin-Probst syndrome but may represent a rare benign variant. While it
is not trivial to prove that a given variant is NOT involved in XLID, the
aggregate evidence presented here suggests that the role of RAB40AL in
XLID and in particular, that of the p.D59G substitution in Martin-Probst
syndrome should be revisited.
Response to "Do patients with single NLRP7 private variants have a
genetic predisposition to hydatidiform moles and reproductive wastage?"
Peter H Dixon and Rosemary A Fisher
We thank Professor Slim for her interest in our article "Mutations in
NLRP7 are associated with diploid biparental hydatidiform moles, but not
androgenetic complete moles" [1]. We would like to confirm that, as stated
in the methods...
Response to "Do patients with single NLRP7 private variants have a
genetic predisposition to hydatidiform moles and reproductive wastage?"
Peter H Dixon and Rosemary A Fisher
We thank Professor Slim for her interest in our article "Mutations in
NLRP7 are associated with diploid biparental hydatidiform moles, but not
androgenetic complete moles" [1]. We would like to confirm that, as stated
in the methods, all nine patients in the recurrent androgenetic mole
cohort were shown, by fluorescent microsatellite genotyping of DNA from
parental blood and molar tissue, to have recurrent moles of androgenetic
origin. For brevity, references to the three cases that were included in
previous studies were cited and a single case used as an example of the
differential diagnosis of diploid biparental and androgenetic hydatidiform
moles in the supplementary materials. Of the six novel cases described in
the article, three separate molar pregnancies were analysed in five cases.
In one case, only a single molar pregnancy could be genotyped due the
sensitive disposal of tissue from her previous molar pregnancies.
We agree entirely with Professor Slim that when several patients are
found to have a rare variant, not found in controls, that it is important
to test their pathogenicty. However, in the field of reproductive
medicine the rarity of a variant may itself be difficult to determine
until large databases of women of known ethnicity and reproductive status
are available for comparison. We agree that family studies are important
in order that segregation of a variant with the disorder can be assessed
and that algorithms that predict likely pathogenicity are useful. However,
when we stated that predicted pathogenicity scores for some of the
previously described variants of NLRP7 approached 1, we were not providing
new data but simply citing Professor Slim's previous work [2]. Clearly as
Professor Slim states the ideal test for pathogenicity is a functional
assay. We acknowledge the work she has done in developing assays to assess
the function of NLRP7 [3] and we welcome further developments in this
field.
The purpose of our present study was to address the question of
whether NLRP7 mutations, clearly important in the development of recurrent
molar pregnancies of diploid biparental origin [4,5,6,7,8] were associated
with the more common androgenetic molar pregnancies. We approached this by
analyzing DNA from women with multiple androgenetic molar pregnancies as
we hypothesized this group would have the greatest likelihood of
mutations/pathological variants if NLRP7 mutations did have a role in the
development of androgenetic molar pregnancies. We believe that failure to
identify any mutations, known pathological variants or other rare variants
in all but one of the cohort is strong evidence that mutations or variants
in NLRP7 are not associated with androgenetic complete moles. We do not
feel that heterozygosity for a single rare variant, R413Q, of unknown
significance in a single case is evidence that this variant confers a
predisposition to molar pregnancies.
In common with Professor Slim, we look forward to the accumulation of
more data regarding variants of NLRP7 and novel assays that address the
function of both NLRP7 and KHDC3L, a second gene recently shown to be
associated with recurrent moles of diploid biparental origin [9].
References
1. Dixon PH, Trongwongsa P, Abu-Hayyah S, Ng Sze Hwei, Akbar SA,
Khawaja NP, Seckl MJ, Savage PM, Fisher RA. Mutations in NLRP7 are
associated with diploid biparental hydatidiform moles, but not
androgenetic complete moles. J Med Genet 2012;49:206-211.
2. Messaed C, Chebaro W, Roberto RB, Rittore C, Cheung A, Arseneau J,
Schneider A, Chen MF, Bernishke K, Surti U, Hoffner L, Sauthier P, Buckett
W, Qian J, Lau NM, Bagga R, Engert JC, Coullin P, Touitou I, Slim R; H M
Collaborative Group. NLRP7 in the spectrum of reproductive wastage: rare
non-synonymous variants confer genetic susceptibility to recurrent
reproductive wastage. J Med Genet 2011;48:540-548.
3. Messaed C, Akoury E, Djuric U, Zeng J, Saleh M, Gilbert L, Seoud
M, Qureshi S, Slim R. NLRP7, a nucleotide oligomerization domain-like
receptor protein, is required for normal cytokine secretion and co-
localizes with Golgi and the microtubule-organizing center. J Biol Chem
2011;286:43313-43323.
4. Murdoch S, Djuric U, Mazhar B, Seoud M, Khan R, Kuick R, Bagga R,
Kircheisen R, Ao A, Ratti B, Hanash S, Rouleau GA, Slim R. Mutations in
NALP7 cause recurrent hydatidiform moles and reproductive wastage in
humans. Nat Genet 2006;38:300-302.
5. Kou YC, Shao L, Peng HH, Rosetta R, del Gaudio D, Wagner AF, Al-
Hussaini TK, Van den Veyver IB. A recurrent intragenic genomic
duplication, other novel mutations in NLRP7 and imprinting defects in
recurrent biparental hydatidiform moles. Mol Hum Reprod 2008;14:33-40.
6. Wang CM, Dixon PH, Decordova S, Hodges MD, Sebire NJ, Ozalp S,
Fallahian M, Sensi A, Ashrafi F, Repiska V, Zhao J, Xiang Y, Savage PM,
Seckl MJ, Fisher RA. Identification of 13 novel NLRP7 mutations in 20
families with recurrent hydatidiform mole; missense mutations cluster in
the leucine rich region. J Med Genet 2009;46:569-575.
7. Hayward BE, De Vos M, Talati N, Abdollahi MR, Taylor GR, Meyer E,
Williams D, Maher ER, Setna F, Nazir K, Hussaini S, Jafri H, Rashid Y,
Sheridan E, Bonthron DT. Genetic and epigenetic analysis of recurrent
hydatidiform mole. Hum Mutat 2009;30:E629-39.
8. Qian J, Cheng Q, Murdoch S, Xu C, Jin F, Chebaro W, Zhang X, Gao
H, Zhu Y, Slim R, Xie X. The Genetics of Recurrent Hydatidiform Moles in
China: Correlations between NLRP7 Mutations, Molar Genotypes, and
Reproductive Outcomes. Mol Hum Reprod 2011;17:612-619.
9. Parry DA, Logan CV, Hayward BE, Shires M, Landolsi H, Diggle C,
Carr I, Rittore C, Touitou I, Philibert L, Fisher RA, Fallahian M,
Huntriss JD, Picton HM, Malik S, Taylor GR, Johnson CA, Bonthron DT,
Sheridan EG. Mutations causing familial biparental hydatidiform mole
implicate c6orf221 as a possible regulator of genomic imprinting in the
human oocyte. Am J Hum Genet 2011;89:451-458.
We would like to comment on Dixon et al., 2012 who questioned the
pathogenicity of private NLRP7 variants found in a heterozygous state in
singleton cases with one to three hydatidiform moles. The interesting part
of this work is in the analysis of nine patients with recurrent
androgenetic moles despite that only reports demonstrating that three of
these patients had had recurrent androgenetic moles are provided either in...
We would like to comment on Dixon et al., 2012 who questioned the
pathogenicity of private NLRP7 variants found in a heterozygous state in
singleton cases with one to three hydatidiform moles. The interesting part
of this work is in the analysis of nine patients with recurrent
androgenetic moles despite that only reports demonstrating that three of
these patients had had recurrent androgenetic moles are provided either in
the supplementary materials (for case 6)[1] or referenced in the Materials
and Methods and had been previously reported by the same group (for case 2
in Buyukurt et al.[2] and case 1 in van der Smagt et al.[3]). Among patients
with recurrent androgenetic moles, the authors found only one patient with
a non-synonymous variant, R413Q that is not reported in the 1000 Genomes
database. Curiously, we previously reported another novel DNA substitution
affecting the same amino acid, R413W, in a patient with one mole and one
live birth[5].
We agree with the authors that finding a rare or private variant in a
patient but not in controls does not imply its pathogenicity. However,
when several patients, each with a single rare variant, are found, and if
these variants are not found in controls [4-6], such variants cannot be
ignored, and the question of their pathogenicity should be raised and
experimental methods addressing this question should be performed. Our
group has reported ten different variants in heterozygous state in
patients with one to three moles, but not in our controls. Determining the
pathogenicity of private missense variants is very challenging in human
genetics. Below, we discuss the arguments that are in favour of, or
against, the pathogenicity of the private missense we reported in
heterozygous state.
First, a good and simple genetic argument to determine if a variant
is pathogenic is its absence in controls, which was done for every
variant. The fact that some of these variants were later reported in some
populations in the 1000 Genomes database is not against their involvement
in the disease. Because in these populations, these variants were found at
low frequencies that are very close to the incidences of sporadic moles in
these populations. Basically, the definition of a susceptibility variant
implies its presence in the general population and only a subset of the
subjects carrying it will develop the disease.
Second, another good genetic argument is to show segregation of the
variant in question in families with other mutations but on different
haplotypes. This was done for one missense, A719V, that we reported in two
patients in a heterozygous state[4, 5,6]. This variant was recently reported
in a fourth patient and again in a heterozygous state and not in controls
[7]. Definitely, more data are needed for the other variants.
Third, as mentioned by Dixon et al., the predicted pathogenicity
scores by Polyphen-2 for seven of the ten variants we reported as single
defective alleles are equal or higher than the predicted pathogenicity
scores for missenses seen in patients with two defective alleles.
Fourth, to date, the only known functional role of NLRP7 is its
requirement for normal IL1? secretion by peripheral blood mononuclear
cells that we demonstrated in cells carrying different NLRP7 mutations [8]
and was confirmed using independent in vitro studies [9]. To investigate
whether the identified single rare variants in our patients affect IL1?
secretion, we had performed the cytokine assay on patients cells carrying
each of the four variants, C399Y, G380R, A719V (Fig. 1 in8), and R413W
(unpublished data), in a heterozygous state, and again these cells
displayed reduced IL1? and TNF secretion.
Fifth, the reproductive outcomes of patients with one defective allele are
milder (approximately 81.6% reproductive wastage, 18.4% live birth) than
those of patients with two defective alleles (97.5% reproductive wastage,
2.5% live births) [5] and more severe than those of patients with sporadic
moles (10-22% reproductive wastage, 90-78% live births) [10].
One of the arguments used by Dixon et al., [1] is that androgenetic
moles are not caused by inherited variants is the fact that androgenetic
moles have not been seen in families. While we agree with this good
argument, we believe that this may not be the only explanation. Another
possibility is that a genetic defect leading to an androgenetic mole
implies having an oocyte whose pronucleus, by as yet unknown mechanisms,
is not able to meet and fuse with the male pronucleus and form a diploid
biparental zygote. Such defect may be very severe, lethal, and not
compatible with the life of the patient when caused only by a genetic
defect in a homozygous state. However, in a heterozygous state, such
defect would be expected to be milder, compatible with the life of the
patient, and will confer genetic susceptibility to androgenetic moles only
in few of her pregnancies when combined with other environmental and/or
genetic factors.
Taking into consideration the emerging views about the mechanisms
leading to androgenetic moles and the presence of complex postzygotic
aneuploidies at their origin, it is therefore unlikely to see the same
resulting parental contribution to products of conception occurring in
other family members and consequently such conceptions will have other
histopathological features and lead to other forms of reproductive wastage
(such as spontaneous abortions, blighted ovum, ectopic pregnancies, etc.).
This would make it difficult to health care professionals to connect these
different clinical entities under the same unifying common defect
segregating in the family. We did notice familial aggregation of
reproductive wastage in the relatives of some patients with moles but
these are difficult to detect and require well-prepared questionnaire and
pedigrees. In few instances, we saw patients with sporadic moles who
reported the occurrence of moles in their mothers. Although, it is
impossible to review the histopathology of the mother's moles to validate
the patients' statements, which is a real limitation in this research
field, however, based on family history, there are rare cases with
dominant transmission of a mild genetic susceptibility. Because males do
not manifest moles, theoretically, only 50% of families of patients who
carry predisposing genetic variants are at risk to manifest reproductive
wastage and of these families only those with females who have tried to
conceive may manifest the disease. For all these reasons and the genetic
complexity of the mechanisms leading to androgenetic moles, we believe
that a very small fraction of patients with a single missense "mutation"
would be expected to have another member who had had androgenetic moles.
In conclusion, we agree with Dixon et al., that recurrent
androgenetic moles do not seem to be caused by a strong causal genetic
defect. However, we believe that there are several arguments, at least for
the time being, indicating that some of the single rare variants in NLRP7
predispose the patients to moles and reproductive wastage. With the
advances in this field, the accumulation of more data from various groups,
and the development of additional functional tests to determine easily the
pathogenicity of rare variants of unknown significance, patients with one
mutation or one private variant can be assured that their chances of
having live births are much higher than patients with two defective
alleles5.
References
1 Dixon PH, Trongwongsa P, Abu-Hayyah S, Ng SH, Akbar SA, Khawaja NP,
Seckl MJ, Savage PM, Fisher RA. Mutations in NLRP7 are associated with
diploid biparental hydatidiform moles, but not androgenetic complete
moles. J Med Genet 2012;49(3):206-11.
2 Buyukkurt S, Fisher RA, Vardar MA, Evruke C. Heterogeneity in
recurrent complete hydatidiform mole: presentation of two new Turkish
families with different genetic characteristics. Placenta 2010;31(11):1023
-5.
3 van der Smagt JJ, Scheenjes E, Kremer JA, Hennekam FA, Fisher RA.
Heterogeneity in the origin of recurrent complete hydatidiform moles: not
all women with multiple molar pregnancies have biparental moles. Bjog
2006;113(6):725-8.
4 Deveault C, Qian JH, Chebaro W, Ao A, Gilbert L, Mehio A, Khan R,
Tan SL, Wischmeijer A, Coullin P, Xie X, Slim R. NLRP7 mutations in women
with diploid androgenetic and triploid moles: a proposed mechanism for
mole formation. Hum Mol Genet 2009;18(5):888-97.
5 Messaed C, Chebaro W, Roberto RB, Rittore C, Cheung A, Arseneau J,
Schneider A, Chen MF, Bernishke K, Surti U, Hoffner L, Sauthier P, Buckett
W, Qian J, Lau NM, Bagga R, Engert JC, Coullin P, Touitou I, Slim R. NLRP7
in the spectrum of reproductive wastage: rare non-synonymous variants
confer genetic susceptibility to recurrent reproductive wastage. J Med
Genet 2011;48(8):540-8.
6 Qian J, Cheng Q, Murdoch S, Xu C, Jin F, Chebaro W, Zhang X, Gao H,
Zhu Y, Slim R, Xie X. The Genetics of Recurrent Hydatidiform Moles in
China: Correlations between NLRP7 Mutations, Molar Genotypes, and
Reproductive Outcomes. Mol Hum Reprod 2011;17(10):612-9.
7 Landolsi H, Rittore C, Philibert L, Hmissa S, Gribaa M, Touitou I,
Yacoubi MT. NLRP7 mutation analysis in sporadic hydatidiform moles in
Tunisian patients: NLRP7 and sporadic mole. Arch Pathol Lab Med
2012;136(6):646-51.
8 Messaed C, Akoury E, Djuric U, Zeng J, Saleh M, Gilbert L, Seoud M,
Qureshi S, Slim R. NLRP7, a NOD-like receptor protein, is required for
normal cytokine secretion and co-localizes with the Golgi and the
microtubule organizing center. J Biol Chem 2011;286(50):43313-433123.
9 Khare S, Dorfleutner A, Bryan NB, Yun C, Radian AD, de Almeida L,
Rojanasakul Y, Stehlik C. An NLRP7-containing inflammasome mediates
recognition of microbial lipopeptides in human macrophages. Immunity
2012;36(3):464-76.
10 Lan Z, Hongzhao S, Xiuyu Y, Yang X. Pregnancy outcomes of patients
who conceived within 1 year after chemotherapy for gestational
trophoblastic tumor: a clinical report of 22 patients. Gynecol Oncol
2001;83(1):146-8.
I think this is a wonderful article, especially since it presents
path breaking evidence regarding the origins of the RAPSYN mutations. The
subject of Congenital Myesthenic Syndromes is now getting its much needed
attention, and such work will go a long way for this cause.
Letter to Editor Shaheen et al. 1 recently reported a homozygous 5 bps deletion mutation (c.1299_1303delTAAG; p.Phe433Leufs*6) in the human polo-like kinase 4 (PLK4,MIM 605031) gene and proposed that it is a compelling candidate for primordial dwarfism (PD). Autozygosity mapping and LOD score, method of estimating linkage distances, are adopted for the novel locus identification. Candidate gene hunting among 144 in the r...
I have read all the respective article and I agreed to most of the findings. Recently, our group has been working with metabolomics towards lipodystropy and we did found similar findings. Recently it has been reported (Abael et al., 2010) that the changes in local thyroid hormone (TH) metabolism may occur in areas with lipoatrophy. These changes could be because of different molecular mechanisms (for example; levels of...
C-terminus truncation of Seipin as a good potential sign of diseases
Wei-Li Yu and Yun Sun
Seipin is a transmembrane protein of the endoplasmic reticulum with N, C-terminus residing the intracytoplasmic side.1 2 Loss of Seipin function has been shown to lead to severe lipodystrophy, motor neuropathy and silver syndrome.3 However, its molecular mechanism is still unknown. Recently Guillén-Navarro E et al 4...
We found this paper to be immensely informative while researching junctional epidermolysis bullosa (JEB) for a particular clinical case, which is described below. During the course of testing for this particular case we found evidence suggesting that that the D982G mutation in LAMB3 may not be disease-causing.
In their paper, Varki, Sadowski, and Pfender et al. present the case of an eight-month-old male patie...
RSS was first described in 1953 [1]. It is a clinically and genetically heterogeneous condition. Clinical diagnosis is based on various characteristics including slow growth before and after birth, relative macrocephaly, a prominent forehead at a young age, hemihypotrophy, and fifth finger clinodactyly. Five different diagnostic scoring systems of RSS have been published. These systems take into account most major clini...
In 2007, Netchine et al. identified imprinting center region I (ICRI) loss of methylation (LOM) as a cause of typical Russell Silver syndrome (RSS) in 37 of 58 subjects who met their recruitment criteria of intrauterine growth retardation (IUGR/SGA) plus at least 3 of 5 criteria: 1) postnatal growth retardation; 2) relative macrocephaly at birth; 3) prominent forehead during early childhood; 4) body asymmetry, and; 5) fe...
Re: Disruption of RAB40AL function leads to Martin-Probst syndrome, a rare X-linked multisystem neurodevelopmental human disorder. Bedoyan JK, Schaibley VM, Peng W, Bai Y, Mondal K, Shetty AC, Durham M, Micucci JA, Dhiraaj A, Skidmore JM, Kaplan JB, Skinner C, Schwartz CE, Antonellis A, Zwick ME, Cavalcoli JD, Li JZ, Martin DM. J Med Genet. 2012 May;49(5):332- 40.
With great interest we have read the article by B...
Response to "Do patients with single NLRP7 private variants have a genetic predisposition to hydatidiform moles and reproductive wastage?"
Peter H Dixon and Rosemary A Fisher
We thank Professor Slim for her interest in our article "Mutations in NLRP7 are associated with diploid biparental hydatidiform moles, but not androgenetic complete moles" [1]. We would like to confirm that, as stated in the methods...
We would like to comment on Dixon et al., 2012 who questioned the pathogenicity of private NLRP7 variants found in a heterozygous state in singleton cases with one to three hydatidiform moles. The interesting part of this work is in the analysis of nine patients with recurrent androgenetic moles despite that only reports demonstrating that three of these patients had had recurrent androgenetic moles are provided either in...
I think this is a wonderful article, especially since it presents path breaking evidence regarding the origins of the RAPSYN mutations. The subject of Congenital Myesthenic Syndromes is now getting its much needed attention, and such work will go a long way for this cause.
Conflict of Interest:
None declared
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