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.
We have read the entire paper with great care. We totally agree with
the findings of the respected authors in this respective article. The
article seems to be used by many researchers as a reference article so we
need to update the status of SMA diagnosis for non deleted SMA patients.
Many new approaches have been employed to diagnose non deleted SMA. One
of such methods is long range PCR method (LR-PCR) (Clemont et al....
We have read the entire paper with great care. We totally agree with
the findings of the respected authors in this respective article. The
article seems to be used by many researchers as a reference article so we
need to update the status of SMA diagnosis for non deleted SMA patients.
Many new approaches have been employed to diagnose non deleted SMA. One
of such methods is long range PCR method (LR-PCR) (Clemont et al., 2004).
Secondly, we can not just focus on the mutations described in this
article. We need to focus on all known mutations in the SMN1 gene in non
deleted SMA patients. Although Clermont and colleagues claimed that 90% of
the mutations in the SMN1 gene can be found by their method (Clermont et
al.,2004), yet many other groups have reported individual mutations. We
would like to enumerate the list of all these mutations. All the mutations
are divided into four main groups; missence mutation, Nonsense mutation,
Frame-shift mutation and Splice site mutations.
The missence mutations (total 25) have been reported in Ex.1 in type
II and III SMA patients (Parsons et al., 1998), Ex. 2a in type II and III
SMA patients (Sun et al., 2005), Ex.3 in type I (Cusco et al., 2004,
Clermont et al., 2004, Prior et al., 2007, Sun et al., 2005, Koatni et
al., 2007), Ex.3 in type II (Clermont et al., 2004, Sun et al., 2005),
Ex.3 in type III SMA patient (Sun et al., 2005, Ex.4 in type I SMA patient
(Zapletalova et al., 2007), Ex. 6 in type III SMA patients (Rochette et
al., 1997, Clermont et al., 2004, Sun et al., 2005, Hahnen et al., 1997,
Parson et al., 1998, Wirth et al., 1999), Ex.6 in type I SMA patient
(Clermont et al., 2004), Ex.6 in type II SMA patient (Alias et al., 2009,
Prior et al., 2007, Lefebvre et al., 1995, Wirth et al., 1999, Rochette et
al., 1997, Clermont et al., 2004, Zapletalova et al., 2007, Hahnen et al.,
1997, Parson et al., 1998, Sun et al., 2005, Ex.6 in type III SMA patients
(Hahnen et al., 1997, Parsons et al., 1998, Wirth et al., 1999, Sun et
al., 2005, Zapletalova et al., 2007, Alias et al., 2009, Burglen et al.,
1996, Skordiset et al., 2001), Ex.7 in type I SMA patient (Talbot et al.,
1997) and Ex.7 in type II and III SMA patients (Wang et al., 1998).
The nonsense mutations (total 5) were curated to be included in Ex.1 in
type I SMA patient (Wirth et al., 1999), Ex.1 in type III SMA patient (Sun
et al., 2005), Ex.3 in type II SMA patient (Sossi et al., 2001, Prior et
al., 2007), Ex.3 in type III SMA patient (Wirth et al., 1999, Sun et al.,
2005, Sossi et al., 2001, Prior et al., 2007), Ex.3 in type I SMA patient
(Bricchta et al., 2008), Ex.4 in type I SMA patient (Alias et al., 2009),
Ex.5 in type I SMA patient (Tsai et al., 2001).
Considering the fram-shift mutations (total 18), it included mutation in
Ex.1 of type I SMA patient (Wirth et al., 1999), Ex.1 in type III SMA
patient (Wirth et al., 1999), Ex.2a in type I SMA patient (Prior et al.,
2007, Zapletalova et al., 2007), Ex.2a in type I SMA patient (Wirth et
al., 1999, Alias et al., 2008), Ex.2b in type I SMA patient (Clermont et
al., 2004), Ex. 2b in type III SMA patient (Wirth et al., 1999), Ex.3 in
type I SMA patient (Brahe et al., 1996, Sossi et al., 2001, Alias et al.,
2008), Ex.3 in type II SMA patient (Bussaglia et al., 1995, Martin et al.,
2002, Cusco et al., 2003, Alias et al., 2008), Ex.3 in type III SMA
patient (Alias et al., 2008, Clermont et al., 2004, Bussaglia et al.,
1995, Martin et al., 2002, Cusco et al., 2003), Ex.4 in type I SMA patient
(Clermont et al., 1997, Clermont et al., 2004), Ex.4 in type II SMA
patient (Parons et al., 1998, Wirth et al., 1999), Ex.4 in type III SMA
patient (Parson et al., 1998), Ex.5 in type I, II and III SMA patients
(Wirth et al., 1999, Clermont et al., 2004), Ex.6 in type I, II and III
SMA patients (Wirth et al., 1999, Clermont et al., 2004, Parsons et al.,
1996, Parsons et al., 1998, Martin et al 2002, Clermont et al., 2004,
Alias et al., 2008, Martin et al., 2002).
The splice site mutations in the SMN1 gene in non deleted SMA patients
include 40Int.4 in type I SMA patient (Brichta et al., 2008), 41Int.6 in
type I SMA patient (Martin et al., 2002), 42Int.6 in type I SMA patient
(Eggermann et al., 2008), 43Int.6 in type I SMA patient (Lefebvre et al.,
1995), 44Int.7 in type I SMA patient (Wirth et al., 1999) and 45Int.7 in
type II SMA patient (Lefebvre et al., 1995).
The copy number analysis of the SMN1 gene is not enough as the SMA
modified genes; SMN2 and NAIP are reported to modify the disease severity
(Watihayati et al., 2009). We will emphasize that the title of the article
is making the readers confusing as considering the article to be the
diagnostic protocol for the spinal muscular atrophy in non deleted SMA
patients. The severity of the disease could be estimated by many
parameters even in the non deleted SMA patients and recently published
report has prooven that (Watihayati et al., 2009) beside the report of
Teguh and colleagues which states that only PCR detection of exon7 of the
SMN1 is enough to diagnose SMA (Teguh et al., 2011) but yet the authors
did not explain the diagnosis of non deleted SMA patients. Very humbly we
would like to add this response with a request to the respected authors to
consider the findings of SMN2 copy number and the NAIP gene deletion with
the available data of this patient.
It was with great interest that we have read the recent article published by Kamath et al. [1] dealing with NOTCH2 mutations in patients affected by Alagille syndrome (ALGS) negative for JAG1 gene mutations and rearrangements. This original article brings relevant information about the mutation frequencies and genotype-phenotype data regarding NOTCH2 gene. Previously only two mutations, one missense and one splicing, have been rep...
It was with great interest that we have read the recent article published by Kamath et al. [1] dealing with NOTCH2 mutations in patients affected by Alagille syndrome (ALGS) negative for JAG1 gene mutations and rearrangements. This original article brings relevant information about the mutation frequencies and genotype-phenotype data regarding NOTCH2 gene. Previously only two mutations, one missense and one splicing, have been reported in two families with ALGS and renal disease [2]. Here we report a family with two siblings affected by a severe cholestasis carrying a maternal inherited frameshift mutation in exon 18 (NM_024408.2:c.2765del;p.Asn922MetfsX9) of NOTCH2 gene. The novel unreported variant was predicted to activate the nonsense mediated mRNA decay and is localized on EGF-like 24 domain of the protein. Moreover, it was absent in the unaffected father and in the third unaffected sibling such as in a cohort of 566 healthy control alleles. Subsequent analysis of genomic DNA from maternal healthy grandparents indicated that the mutation had occurred de novo in the mother. After a deep clinical and instrumental re-evaluation, our patients did not show any cardiac disease, skeletal, ocular abnormalities or facies typical of ALGS. NOTCH2 sequencing analysis has been performed in other 9 cases negatives for JAG1 mutations. No other patient with NOTCH2 mutations has been identified.
The two siblings underwent liver transplantation due to the severe liver dysfunction, while the mother presented only a mild hypercholesterolemia, suggesting a wide variable expressivity of the disease in the family. Also the patient described by Kamath et al. [1], carrying a frameshift mutation in exon 16 (p.Ser856fs16X), had only liver involvement further confirming the phenotypic variability associated with this inherited disease. The variable expressivity is typical of patients affected by ALGS carrying mutations in JAG1 gene. Classic diagnostic criteria for ALGS combine the presence of bile duct paucity on liver biopsy with three of five systems affected: liver, heart, skeleton, eye and dysmorphic facies. Recently, it has been shown that JAG1 mutations are present also in patients having only one or two ALGS criteria [3]. This finding is not surprising, considering that even family members sharing the same mutation can have a wide spectrum of phenotypic manifestations ranging from life-threatening cardiac or liver disease to subtle or null clinical features. In our experience, JAG1 mutations are identified in 93% of patients with three or more diagnostic criteria, while they are rarely identified (4 mutated out of 55 indexes analyzed) in patients having cholestasis alone or associated to another ALGS diagnostic feature. The low mutational detection rate in JAG1 and NOTCH2 genes leads to question the real utility to perform the sequencing analysis of such large genes in a clinical context in this cohort of patients. The "cascade" screening of these genes is expensive and time consuming in isolated cholestasis associated or not with others minor clinical features creating anxiety and false expectations in families. For this reasons, we believe that a new strategy of analysis, based on targeted next-generation sequencing (NGS) of all genes causative of liver diseases, may be more appropriate for characterizing atypical ALGS patients. A comprehensive NGS analysis of liver genes may be more useful for clinicians, patients and families decreasing time and costs by ending the diagnostic odyssey as already demonstrated for other genetic conditions.
References:
1. Kamath BM, Bauer RC, Loomes KM, Chao G, Gerfen J, Hutchinson A, Hardikar W, Hirschfield G, Jara P, Krantz ID, Lapunzina P, Leonard L, Ling S, Ng VL, Hoang PL, Piccoli DA, Spinner NB. NOTCH2 mutations in Alagille syndrome. J Med Genet 2012;49:138-44.
2. McDaniell R, Warthen DM, Sanchez-Lara PA, Pai A, Krantz ID, Piccoli DA, Spinner NB. NOTCH2 mutations cause Alagille syndrome, a heterogeneous disorder of the notch signaling pathway. Am J Hum Genet. 2006;79:169-73.
3. Guegan K, Stals K, Day M, Turnpenny P, Ellard S. JAG1 mutations are found in approximately one third of patients presenting with only one or two clinical features of Alagille syndrome. Clin Genet 2011. doi: 10.1111/j.1399-0004.2011.01749.x. [Epub ahead of print].
It was with great interest that I read the study by Tang and co-
authors [1], in which they discovered twenty-five novel mutations in DNA
polymerase gamma. Based on the presence of p.G268A substitution in
heterozygosis in 19 subjects from a cohort of 2697 unrelated patients,
they proposed to reclassify this mutation as a neutral polymorphism or a
polymorphic modifier rather than a pathological mutation. Smith and co-
auth...
It was with great interest that I read the study by Tang and co-
authors [1], in which they discovered twenty-five novel mutations in DNA
polymerase gamma. Based on the presence of p.G268A substitution in
heterozygosis in 19 subjects from a cohort of 2697 unrelated patients,
they proposed to reclassify this mutation as a neutral polymorphism or a
polymorphic modifier rather than a pathological mutation. Smith and co-
authors [2] confirmed that POLG G268A is not pathogenic but represent
neutral polymorphism on the basis of the presence of this mutations in
three healthy subjects and on the basis of the frequencies of the allele
p.G268A in their patient cohort, which were similar to those found in a
control population of European origin by the NHLBI exome sequencing
project [3].
I and co-authors previously demonstrated that in yeast the mip1G224A
allele, corresponding to the human p.G268A substitution, was associated
with a 2.2-fold increase in petite frequency, which is the frequency of
mutants with large deletions and/or loss of mtDNA [4]. A further analysis
made in our laboratory on yeast mip1 mutations corresponding to human
substitutions classified as neutral SNPs [5] conserved from yeasts to
mammals (E. Baruffini and T. Lodi, unpublished results), suggested the
existence of a class of substitutions, that also includes G224A, which are
not neutral. These mutations caused a 1.5 to 2.5-fold increase in petite
frequency, which was lower compared to the petite frequency caused by
mutations recognized as pathological, for which at least a 10-fold
increase in petite frequency or the total loss of mtDNA were observed in
our laboratory [4, 6-9]. This class includes also the mip1E900G and
mip1Q766C alleles, corresponding to the human p.E1143G and p.R964C
substitutions, respectively. The former (2-fold increase in petite
frequency) is a substitution classified in humans as a phenotypic modifier
that can modulate disease mutations [10, 11]. The latter (2-fold increase)
seems to be pathological in humans when in heterozygosis with p.A862T
[8,12] or with p.A962T [1] but not pathological in homozygosis [13];
however it is associated with mitochondrial toxicity susceptibility to
stavudine both in humans [13] and in yeast [14] and the mutant DNA
polymerase gamma showed an impaired polymerase activity [15].
Conclusion: analysis in yeast suggests that p.G268A is neither a
pathological mutation nor a neutral SNP. It can be classified, together
with R964C and E1143G, as a "phenotypic modifier", as suggested by
Copeland [10], as an "unclassified variant", as suggested by Tang and co-
authors [1] or as an "Ecogenetic Single Nucleotide Variant (ESNV)", as
suggested by Saneto and Naviaux for genetic variations whose phenotypic
expression is determined by interaction with genetic, epigenetic and
environmental factors [16]. In general, these observations suggest that
the validation of the pathological significance of novel mutations, whose
discovery is exponentially increasing thanks to the next generation
sequencing, can take advantage, when possible, of experimental analysis in
model systems to confirm or disavow their role in the disease.
References
1. Tang S, Wang J, Lee NC, Milone M, Halberg MC, Schmitt ES, Craigen WJ,
Zhang W, Wong LJ. Mitochondrial DNA polymerase gamma mutations: an ever
expanding molecular and clinical spectrum. J Med Genet 2011;48:669-681.
2. Smith C. POLG p.G268A and p.G517V are not pathogenic mutations. J
MedGenet 2011; eletter
3. NHLBI exome sequencing project, https://esp.gs.washington.edu/drupal/
4. Baruffini E, Lodi T, Dallabona C, Puglisi A, Zeviani M, Ferrero I.
Genetic and chemical rescue of the Saccharomyces cerevisiae phenotype
induced by mitochondrial DNA polymerase mutations associated with
progressive external ophthalmoplegia in humans. Hum Mol Genet 2006;15:2846
-2855.
5. dbSNP, http://www.ncbi.nlm.nih.gov/snp/
6. Baruffini E, Ferrero I, Foury F. Mitochondrial DNA defects in
Saccharomyces cerevisiae caused by functional interactions between DNA
polymerase gamma mutations associated with disease in human. Biochim
Biophys Acta 2007;1772:1225-1235.
7. Spinazzola A, Invernizzi F, Carrara F, Lamantea E, Donati A, Dirocco M,
Giordano I, Meznaric-Petrusa M, Baruffini E, Ferrero I, Zeviani M.
Clinical and molecular features of mitochondrial DNA depletion syndromes.
J Inherit Metab Dis 2009;32:143-158.
8. Stricker S, Pr?ss H, Horvath R, Baruffini E, Lodi T, Siebert E, Endres
M, Zschenderlein R, Meisel A.J. A variable neurodegenerative phenotype
with polymerase gamma mutation. J Neurol Neurosurg Psychiatry 2009;80:1181
-1182.
9. Baruffini E, Horvath R, Dallabona C, Czermin B, Lamantea E, Bindoff L,
Invernizzi F, Ferrero I, Zeviani M, Lodi T. Predicting the contribution of
novel POLG mutations to human disease through analysis in yeast model.
Mitochondrion 2011;11:182-190.
10. Human DNA Polymerase Gamma Mutation Database,
http://tools.niehs.nih.gov/polg/
11. Chan SS, Longley MJ, Copeland WC. Modulation of the W748S mutation in
DNA polymerase gamma by the E1143G polymorphismin mitochondrial disorders.
Hum Mol Genet 2006;15:3473-3483.
12. Wong LJ, Naviaux RK, Brunetti-Pierri N, Zhang Q, Schmitt ES, Truong C,
Milone M, Cohen BH, Wical B, Ganesh J, Basinger AA, Burton BK, Swoboda K,
Gilbert DL, Vanderver A, Saneto RP, Maranda B, Arnold G, Abdenur JE,
Waters PJ, Copeland WC. Molecular and clinical genetics of mitochondrial
diseases due to POLG mutations. Hum Mutat 2008;29:E150-E172.
13. Yamanaka H, Gatanaga H, Kosalaraksa P, Matsuoka-Aizawa S, Takahashi T,
Kimura S, Oka S. Novel mutation of human DNA polymerase gamma associated
with mitochondrial toxicity induced by anti-HIV treatment. J Infect Dis
2007;195:1419-1425.
14. Baruffini E, Lodi T. Construction and validation of a yeast model
system for studying in vivo the susceptibility to nucleoside analogues of
DNA polymerase gamma allelic variants. Mitochondrion 2010;10:183-187.
15. Bailey CM, Kasiviswanathan R, Copeland WC, Anderson KS. R964C mutation
of DNA polymerase gamma imparts increased stavudine toxicity by decreasing
nucleoside analog discrimination and impairing polymerase activity.
Antimicrob Agents Chemother 2009;53:2610-2612.
16. Saneto RP, Naviaux RK. Polymerase gamma disease through the ages. Dev
Disabil Res Rev 2010;16:163-174.
The respective article was well read by us. We agree with the
precious scientific findings by the authors but at the same time we would
like to recall the two very basic fundamental functions of CBP, which
involve CBP as a bridging molecule and a cofactor (Montmini et al., 1986)
for CREB modulated gene expression and histone acetyltransferase activity
of CBP on CREB modulated gene expression (Lu et al., 2003) specificall...
The respective article was well read by us. We agree with the
precious scientific findings by the authors but at the same time we would
like to recall the two very basic fundamental functions of CBP, which
involve CBP as a bridging molecule and a cofactor (Montmini et al., 1986)
for CREB modulated gene expression and histone acetyltransferase activity
of CBP on CREB modulated gene expression (Lu et al., 2003) specifically
and on histone acetylation in general.
This study specifically targeted lymphoid cell lines from patients
with Rubinstein-Taybi syndrome but it has provided a new horizon towards
defining some crucial event as the respective authors have tried to
correlate the general post-transcriptional events (via histone acetylation
level) with the transcriptional events (by CBP and p300 as a co-
activators/cofactors). The study has given the overall status of the
histone acetylation level and mutations within the CBP gene but yet unable
to describe the role of these mutations in CBP specifically to any
specific genes/motifs within the whole genome or in the CRE elements in
the promoter region of different genes, which could play a vital role in
circumscribing the clinical severity of the disease as has been in seen in
a report from Sarmila et al., 2004; which stated the role in
overexpressing the SMN genes associated with Spinal Muscular Atrophy. The
disease shared quite similar clinical features with Rubinstein-Taybi
syndrome with a vast heterogeneity.
The transcription factors are reported to be phosphorylated by
Protein Kinase K (PKA) which is dependent on increase level of cAMP. CREB
has been reported to be the best linked between PKA activation and gene
transcription (Montmini et al., 1986). Authors also studied p300 which has
been reported to interact with many transcription factors, reflecting the
role of p300 and CBP as co-activators more generally in signal integration
(Goodman et al., 2000).
Deficit in histone acetylation in cell lines in this study can be
correlated to the defect in histone acetyltransferase activity of CBP in
general on the whole genome but the specific effect through the invitro
CREB acetylation must be considered by the respective authors by atleast
the linkage analysis of the CREB induced genes in the described nine
patients in this study. We assume, by doing so, the role of CREB or CRE
modulated disease severity could be ruled out. We have done the same for
Spinal Muscular Atrophy (data not published yet).
Similarly, the use of histone deacetylases (HDACi)followed by the the
acetylation status is too general for the entire genome. For sure, HDACi
will recover the "acetyltransferase activity" of CBP but the effect of
HDACi on the coactivation function of the CBP is not well explained. Any
of the histone deacetylases, will increase the whole genome expression but
defining the specific HDACi molecule for a specific gene is the need for
decreasing and circumscribing the clinical severity of Rubinstein-Taybi
syndrome. Some studies have been reported explaining the effect of HDACi
in SMA which make use of several molecules (Sumner et al., 2006 and
Brichta et al., 2003, Andreassi et al., 2004).
There is a need to explore the specific genes for their epigentic
control and effect in Rubinstein-Taybi syndrome therefore, further studies
are needed to confirm the effect of these mutation and histone
acetylation; towards defining specific genes in circumscribing the
clinical severity of Rubinstein-Taybi syndrome and to develop a strategy
for gene therapy.
References:
1. Montminy MR, Bilezikjian LM, (1987). Binding of a nuclear protein
to the cyclic-AMP response element of the somatostatin gene. Nature.
15;328(6126):175-8.
2. Lu Q, Hutchins AE, Doyle CM, Lundblad JR, Kwok RP, (2003).
Acetylation of cAMP-responsive element-binding protein (CREB) by CREB-
binding protein enhances
CREB-dependent transcription. J Biol Chem. 2;278(18):15727-34.
3. Sarmila Majumder, Saradhadevi Varadharaj, Kalpana Ghoshal, Umrao
Monani, Arthur H. M. Burghes, Samson T. Jacob, (2004). Identification of a
Novel Cyclic AMP-response Element (CRE-II) and the Role of CREB-1 in the
cAMP-induced Expression of the Survival Motor Neuron (SMN) Gene. The
journal of biological chemistry: 279, 15: 14803-1481.
4.Goodman RH, Smolik S, (2000). CBP/p300 in cell growth,
transformation, and development. Genes Dev. 1;14(13):1553-77.
5. Sumner CJ, (2006). Therapeutics development for spinal muscular
atrophy. NeuroRx: 3:235-245.
6. Brichta L, Hofmann Y, Hahnen E, Siebzehnrubl FA, Raschke H,
Blumcke I, Eyupoglu IY, Wirth B, (2003). Valproic acid increases the SMN2
protein level: a well-known drug as a potential therapy for spinal muscula
In their recently published paper describing mutations in
mitochondrial DNA polymerase gamma, Tang et al.(1) propose that the POLG
p.G268A (c.803G>C) and p.G517V (c.1550G>T) variants which have
previously been reported as pathogenic mutations should be considered as
unclassified variants that may represent rare neutral polymorphisms or
polymorphic modifiers.
In their recently published paper describing mutations in
mitochondrial DNA polymerase gamma, Tang et al.(1) propose that the POLG
p.G268A (c.803G>C) and p.G517V (c.1550G>T) variants which have
previously been reported as pathogenic mutations should be considered as
unclassified variants that may represent rare neutral polymorphisms or
polymorphic modifiers.
We have also identified these variants in our own cohort of 627
patients that were referred with a suspected disorder of mitochondrial DNA
maintenance. We detected p.G268A in 9 individuals (allele frequency
0.72%) of ages from 3 months to 63 years. Symptoms were variable ranging
from severe early onset mitochondrial DNA depletion syndrome to milder
late onset neuropathy/ataxia/ophthalmoplegia. In all 9 cases the variant
occurred as a heterozygous change with no other pathogenic POLG mutation,
suggesting that p.G268A is not a recessive mutation. Parental samples
were available in 3 cases, and for each of these we found the variant in
an unaffected parent, suggesting that p.G268A is very unlikely to be a
dominant mutation. Furthermore, one of the 9 index cases was later found
to be compound heterozygous for pathogenic mutations in another gene
associated with mtDNA maintenance disorders, DGUOK. In another case the
proband had a similarly affected sibling who did not have p.G268A.
Similarly, we have identified p.G517V 8 times (allele frequency
0.64%), always as a heterozygous change with no other pathogenic POLG
mutation. The age of the individuals ranged from 1-81 yrs and the
phenotype varied from infantile epilepsy/failure to thrive to adult onset
ophthalmoplegia/ataxia/myopathy. The unaffected parent of 1 of these
individuals was also heterozygous for p.G517V. A second affected
individual was later found to have pathogenic mutations in RRM2B.
Furthermore, the allele frequencies of p.G268A and p.G517V in our
patient cohort are remarkably similar to those found in a large control
population of European origin (2700 alleles) by the NHLBI exome sequencing
project (2); 0.59% and 0.86% respectively.
Therefore, our data, taken together with that for Tang et al. and the
NHLBI exome sequencing project, confirm that POLG p.G268A and p.G517V are
not pathogenic and are highly likely to represent neutral polymorphisms.
References.
(1) Tang S, Wang J, Lee NC, Milone M, Halberg MC, Schmitt ES, Craigen WJ,
Zhang W, Wong LJ. Mitochondrial DNA polymerase gamma mutations: an ever
expanding molecular and clinical spectrum. J Med Genet 2011;48:669-681.
(2) https://esp.gs.washington.edu/drupal/
Re: Genetic variant in the promoter of connective tissue growth
factor gene confers susceptibility to nephropathy in type 1 diabetes. Wang
et al., J Med Genet 2010; 47:391-397. Doi:10,1136/jmg.2009.073098
It was with great interest that we read the recent study by Wang et
al. on a novel C/G single nucleotide polymorphism (SNP) at position -20 in
the promoter of the connective tissue growth factor (CTGF) gene confe...
Re: Genetic variant in the promoter of connective tissue growth
factor gene confers susceptibility to nephropathy in type 1 diabetes. Wang
et al., J Med Genet 2010; 47:391-397. Doi:10,1136/jmg.2009.073098
It was with great interest that we read the recent study by Wang et
al. on a novel C/G single nucleotide polymorphism (SNP) at position -20 in
the promoter of the connective tissue growth factor (CTGF) gene confers
susceptibility to diabetic nephropathy in patients with type 1 diabetes
(T1D).[1] Based on these findings we studied this SNP in our cohort of T1D
to determine its association with the development of diabetic nephropathy.
This SNP was genotyped in 932 European Caucasoid subjects and failed to
detect the polymorphism.
Connective tissue growth factor (CTGF) is a secreted protein with a
molecular weight at 36-38 kDa and plays an important role in the balance
of degradation and synthesis of extracellular matrix although its
physiological functions are not limited to this.[2] Several studies have
demonstrated that CTGF plays a fundamental role in the histopathological
changes seen in diabetic nephropathy. It has been demonstrated that low
levels of glomerular CTGF are found in normal human glomeruli, but both
mRNA and protein levels of CTGF increase during the early stages of
diabetic nephropathy and continue to increase with disease progressionand
these increases also correlate with the degree of albuminuria.[3]
The CTGF gene is located on Chromosome 6q23 and has 5 exons. Several
SNPs have been identified in the promoter, introns, exons and 3'UTR
regions of the gene.[1,4-6] Some of these SNPs have been studied and shown
to be associated with various conditions including systemic sclerosis and
cardiovascular diseases.[5-6] Addition, Wang et al. report has described a
novel C/G SNP at position -20 in the promoter of the CTGF gene that is
associated with nephropathy in T1D.[1] In this report, 862 subjects from
the DCCT/EDIC cohort of T1D were genotyped. The frequencies of the CC, CG
and GG genotypes were 62.76% (541/862), 31.90% (275/862) and 5.34%
(46/862) in this cohort respectively. The frequency of GG genotype in
patients with microalbuminuia (albumin excretion rate (AER) >40mg/24h)
was significantly higher than patients with AER <40mg/24h, p<0.0001.
The GG genotype was also shown to have greater transcriptional activity
than that of the CG and CC genotypes.
A total of 739 Caucasoid patients with T1D (Female: 402; Male: 347)
and with or without microvascular complications and 193 normal ethnically
matched controls (Female: 101; Male: 92) were recruited in our study.
Patients with T1D had an average age of 30.83 years (range: 1-76 years)
and the average age of onset was 16.86 years (range: <1-52 years) with
an average duration of T1D at 13.98 years (range: 0-55 years). The study
was approved by the Local Research Ethical Committee and informed consent
was obtained from all subjects. All patients have T1D as defined by The
Expert Committee on the Diagnosis and Classification of Diabetes
Mellitus.[7] Normal controls were obtained from cord blood samples
following normal healthy obstetric delivery in Derriford Hospital,
Plymouth.
Genomic DNA was prepared from peripheral and cord blood samples using
the Nucleon II extraction kit (Scotlab, Lanarkshire, UK) following the
manufacture's instruction. DNA samples were sent in 96-well plates to
KBioscioences together with the SNP information published in Wang's
study.[1] The sequence which covers the location of the SNP in bracket:
GTATAAAAGC[C/G]TCGGGCCGCC has been checked and confirmed with the
published sequence of the CTGF gene.[4,8] Genotyping for this SNP was
performed using KASPar assays which are a proprietary in-house system
(KBiosciences, Herts, UK). Unexpectedly, our results showed there was no
SNP at the position -20 of the CTGF gene in our entire population; all
subjects had the CC genotype.
We tried to understand why there were discrepancies between our
findings and those of Wang et al.[1] Wang's study is the only publication
regarding this SNP. There are a number of possible reasons for the
discrepancy. Firstly, with respect of the ethnicity, our studied
population was 100% Caucasian, Wang's subjects from the DCCT/EDIC cohort
of T1D contained 96-97% of Caucasian.[9] The genetic backgrounds might be
different even within Caucasian populations between different geographic
locations.[5,10] but we would expect that the differences in the genetic
backgrounds would cause the differences in the frequency of each genotype
rather than no genetic variants at the position -20 of the CTGF gene.
Secondly, sample size could be an issue, according to Wang's results: the
frequencies of GG and GC were 5.34% and 31.90% respectively in their
population, we should be able to detect about 39 subjects with GG and 235
subjects with GC genotypes out of our 739 subjects with T1D. Therefore, it
is unlikely that our sample size was too small to allow the detection of
the minor genotypes GG or GC. Thirdly, genotyping techniques may give rise
to false positives or negatives. We used a highly reputable commercial
genotyping facility-KBiosciences. Furthermore, our samples have been
extensively genotyped including another SNP (rs9399005) in the CTGF gene
that were typed in parallel to this one (Our unpublished data, 2011).
Wang's study used PCR in their-own laboratory and confirmed this SNP by bi
-directional sequencing. Sequences were detected on a Megabase N500
sequencer and results were analysed with sequencer software (Gene Codes
Corporation, Ann Arbour, Michigan, USA). Consequently, it is unlikely that
technical issues could explain the discrepancy between the sets of
results. Finally, we don't think that the disparate results in this SNP
between the two groups are due to the gender, age, duration of diabetes or
age at onset of diabetes of patients either as the CTGF gene is not
located in the X or Y chromosomes and the age, duration of diabetes and
age at onset of diabetes of patients in both groups were similar. In
conclusion, the reason for this discrepancy is unclear but is probably a
reflection of the heterogeneity of populations. Therefore, further studies
are needed to confirm this SNP from different groups or independent
populations.
References:
1. Wang B, Cater RE, Jaffa MA, et al. Genetic variant in the promoter of
connective tissue growth factor gene confers susceptibility to nephropathy
in type 1 diabetes. J Med Genet 2010;47:391-397.
2. Mason RM. Connective tissue growth factor (CCN2), a pathogenic factor
in diabetic nephropathy. What does it do? How does it do it? J Cell Commun
Signal 2009;3:95-104.
3. Wahab NA, Schaefer L, Weston BS, et al. Glomerular expression of
thrombospondin-1, transforming growth factor beta and connective tissue
growth factor at different stages of diabetic nephropathy and their
interdependent roles in mesangial response to diabetic stimuli.
Diabetologia 2005;48:2650-2660.
4. Blom IE, van Diji AJ, de Weger RA, et al. Identification of human ccn2
(connective tissue growth factor) promoter polymorphisms. J Clin Pathol
Mol Pathol 2001;54:192-196.
5. Granel B, Agriro L, Hachulla E, et al. Association between a CTGF gene
polymorphism and system sclerosis in a French population. J Rheumatol
2010;37:351-358.
6. Cozzolino M, Biondi ML, Banfi E, et al. CCN2 (CTGF) gene polymorphism
is a novel prognostic risk factor for cardiovascular outcomes in
hemodialysis patients. Blood Purif 2010;30:272-276.
7. The Expert Committee on the diagnosis and classification of diabetes
mellitus. Report of the Expert Committee on the diagnosis and
classification of diabetes mellitus. Diabetes Care 2003;26:S5-S20.
8. Homo sapiens chromosome 6, GRCh37.p2 primary reference assembly.
Retrieved on 23rd June 2011 from http://www.ncbi.nlm.nih.gov
9. The Diabetes Control and Complications Trial Research Group. The effect
of intensive treatment of diabetes on the development and progression of
long-term complications in insulin-dependent diabetes mellitus. N Eng J
Med 1993;329:977-986.
10. Rueda B, Simeon C, Hesselstrand R, et al. A large multicenter analysis
of CTGF-945 promoter polymorphism does not confirm association with
systemic sclerosis susceptibility or phenotype. Ann Rheum Dis 2009;68:1618
-1620.
It was with great interest that I read Casasnovas et al article
"Phenotypic Spectrum of MFN2 Mutations in the Spanish Population". The
authors mention the Gly298Arg mutation in one of their families, with 2
affected individuals, and state that this has previously been described.
They refer to Lawson's 2005 article (Ref#10, Lawson VH, Graham BV,
Flanigan KM. Clinical and electrophysiologic features of
CMT2A with mutation...
It was with great interest that I read Casasnovas et al article
"Phenotypic Spectrum of MFN2 Mutations in the Spanish Population". The
authors mention the Gly298Arg mutation in one of their families, with 2
affected individuals, and state that this has previously been described.
They refer to Lawson's 2005 article (Ref#10, Lawson VH, Graham BV,
Flanigan KM. Clinical and electrophysiologic features of
CMT2A with mutations in the mitofusin 2 gene. Neurology 2005;65:197) as
having described this mutation previously.
However, upon careful review of Lawson's article, I only found
mention of this mutation as a SNP found by the Utah researchers in 3% of
their control chromosomes.
Would the authors please comment on what evidence they have that this
is a disease causing mutation, or is this a benign polymorphism? As the
authors mention, this point mutation is in a highly conserved region of
the dynamin like GTPase region of mitofusin 2, and results in a non-
synonymous amino acid change, therefore one would suspect it as disease
causing.
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
We have read the entire paper with great care. We totally agree with the findings of the respected authors in this respective article. The article seems to be used by many researchers as a reference article so we need to update the status of SMA diagnosis for non deleted SMA patients. Many new approaches have been employed to diagnose non deleted SMA. One of such methods is long range PCR method (LR-PCR) (Clemont et al....
It was with great interest that I read the study by Tang and co- authors [1], in which they discovered twenty-five novel mutations in DNA polymerase gamma. Based on the presence of p.G268A substitution in heterozygosis in 19 subjects from a cohort of 2697 unrelated patients, they proposed to reclassify this mutation as a neutral polymorphism or a polymorphic modifier rather than a pathological mutation. Smith and co- auth...
The respective article was well read by us. We agree with the precious scientific findings by the authors but at the same time we would like to recall the two very basic fundamental functions of CBP, which involve CBP as a bridging molecule and a cofactor (Montmini et al., 1986) for CREB modulated gene expression and histone acetyltransferase activity of CBP on CREB modulated gene expression (Lu et al., 2003) specificall...
In their recently published paper describing mutations in mitochondrial DNA polymerase gamma, Tang et al.(1) propose that the POLG p.G268A (c.803G>C) and p.G517V (c.1550G>T) variants which have previously been reported as pathogenic mutations should be considered as unclassified variants that may represent rare neutral polymorphisms or polymorphic modifiers.
We have also identified these variants in our...
Re: Genetic variant in the promoter of connective tissue growth factor gene confers susceptibility to nephropathy in type 1 diabetes. Wang et al., J Med Genet 2010; 47:391-397. Doi:10,1136/jmg.2009.073098
It was with great interest that we read the recent study by Wang et al. on a novel C/G single nucleotide polymorphism (SNP) at position -20 in the promoter of the connective tissue growth factor (CTGF) gene confe...
It was with great interest that I read Casasnovas et al article "Phenotypic Spectrum of MFN2 Mutations in the Spanish Population". The authors mention the Gly298Arg mutation in one of their families, with 2 affected individuals, and state that this has previously been described. They refer to Lawson's 2005 article (Ref#10, Lawson VH, Graham BV, Flanigan KM. Clinical and electrophysiologic features of CMT2A with mutation...
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