Article Text
Abstract
Background Holoprosencephaly (HPE), the most common malformation of the human forebrain, may result from mutations in over 12 genes. Sonic Hedgehog (SHH) was the first such gene discovered; mutations in SHH remain the most common cause of non-chromosomal HPE. The severity spectrum is wide, ranging from incompatibility with extrauterine life to isolated midline facial differences.
Objective To characterise genetic and clinical findings in individuals with SHH mutations.
Methods Through the National Institutes of Health and collaborating centres, DNA from approximately 2000 individuals with HPE spectrum disorders were analysed for SHH variations. Clinical details were examined and combined with published cases.
Results This study describes 396 individuals, representing 157 unrelated kindreds, with SHH mutations; 141 (36%) have not been previously reported. SHH mutations more commonly resulted in non-HPE (64%) than frank HPE (36%), and non-HPE was significantly more common in patients with SHH than in those with mutations in the other common HPE related genes (p<0.0001 compared to ZIC2 or SIX3). Individuals with truncating mutations were significantly more likely to have frank HPE than those with non-truncating mutations (49% vs 35%, respectively; p=0.012). While mutations were significantly more common in the N-terminus than in the C-terminus (including accounting for the relative size of the coding regions, p=0.00010), no specific genotype―phenotype correlations could be established regarding mutation location.
Conclusions SHH mutations overall result in milder disease than mutations in other common HPE related genes. HPE is more frequent in individuals with truncating mutations, but clinical predictions at the individual level remain elusive.
- Holoprosencephaly
- Sonic Hedgehog
- SHH
- genetics
- genome-wide
- academic medicine
- adrenal disorders
- anterior segment disease
- cancer: breast
- cancer: CNS
- cytogenetics
- molecular genetics
- clinical genetics
- developmental
- diagnosis
- guidelines
- congenital heart disease
- epigenetics
- genetic screening/counselling
- aneuploidy
- chromosomal
- ethics
- complex traits
- neurosciences
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- Holoprosencephaly
- Sonic Hedgehog
- SHH
- genetics
- genome-wide
- academic medicine
- adrenal disorders
- anterior segment disease
- cancer: breast
- cancer: CNS
- cytogenetics
- molecular genetics
- clinical genetics
- developmental
- diagnosis
- guidelines
- congenital heart disease
- epigenetics
- genetic screening/counselling
- aneuploidy
- chromosomal
- ethics
- complex traits
- neurosciences
Footnotes
BDS and KAB contributed equally to this work. The views expressed by KAB in this article are those of the author and do not necessarily reflect the official policy or position of the Department of the Army, nor the US government.
Funding This work was supported by the Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Department of Health and Human Services, USA.
Competing interests None.
Patient consent Obtained.
Ethics approval Ethics approval was provided by National Human Genome Research Institute IRB.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement All relevant data are included in this article. All other clinical information specific to patients is managed by their respective clinicians and/or our reference laboratories.