American journal of human genetics
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Case Reports
De Novo Mutations in SLC1A2 and CACNA1A Are Important Causes of Epileptic Encephalopathies.
Epileptic encephalopathies (EEs) are the most clinically important group of severe early-onset epilepsies. Next-generation sequencing has highlighted the crucial contribution of de novo mutations to the genetic architecture of EEs as well as to their underlying genetic heterogeneity. Our previous whole-exome sequencing study of 264 parent-child trios revealed more than 290 candidate genes in which only a single individual had a de novo variant. ⋯ Notably, recurrent mutations accounted for 7/17 of the pathogenic variants identified. As a result of high-depth coverage, parental mosaicism was identified in two out of 14 cases tested with mutant allelic fractions of 5%-6% in the unaffected parents, carrying significant reproductive counseling implications. These results confirm that dysregulation in diverse cellular neuronal pathways causes EEs, and they will inform the diagnosis and management of individuals with these devastating disorders.
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Genome-wide association studies (GWASs) have provided many insights into cancer genetics. However, the molecular mechanisms of many susceptibility SNPs defined by GWASs in cancer heritability and in promoting cancer risk remain elusive. New research strategies, including functional evaluations, are warranted to systematically explore truly causal genetic variants. ⋯ Based on cell proliferation, wound healing, and transwell assays as well as the mouse xenograft model, we identify EPB41 as a HCC susceptibility gene in vitro and in vivo. Consistent with this notion, we note that EPB41 expression is significantly decreased in HCC tissue specimens, especially in portal vein metastasis or intrahepatic metastasis, compared to normal tissues. Our results highlight the involvement of regulatory genetic variants in HCC and provide pathogenic insights of this malignancy via a genome-wide approach.
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Multicenter Study Comparative Study
Penetrance of Hemochromatosis in HFE Genotypes Resulting in p.Cys282Tyr and p.[Cys282Tyr];[His63Asp] in the eMERGE Network.
Hereditary hemochromatosis (HH) is a common autosomal-recessive disorder associated with pathogenic HFE variants, most commonly those resulting in p. Cys282Tyr and p. His63Asp. ⋯ Only males showed differences across genotypes in transferrin saturation levels (100% of homozygotes versus 37.5% of compound heterozygotes with transferrin saturation > 50%; p = 0.003), serum ferritin levels (77.8% versus 33.3% with serum ferritin > 300 ng/ml; p = 0.006), and diabetes (44.7% versus 28.0%; p = 0.03). No differences were found in the prevalence of heart disease, arthritis, or liver disease, except for the rate of liver biopsy (10.9% versus 1.8% [p = 0.013] in males; 9.1% versus 2% [p = 0.035] in females). Given the higher rate of HH diagnosis than in prior studies, the high penetrance of iron overload, and the frequency of at-risk genotypes, in addition to other suggested actionable adult-onset genetic conditions, opportunistic screening should be considered for p.[Cys282Tyr];[Cys282Tyr] individuals with existing genomic data.
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Comparative Study
Truncating Mutations of MAGEL2, a Gene within the Prader-Willi Locus, Are Responsible for Severe Arthrogryposis.
Arthrogryposis multiplex congenita (AMC) is characterized by the presence of multiple joint contractures resulting from reduced or absent fetal movement. Here, we report two unrelated families affected by lethal AMC. By genetic mapping and whole-exome sequencing in a multiplex family, a heterozygous truncating MAGEL2 mutation leading to frameshift and a premature stop codon (c.1996delC, p. ⋯ PWS is associated with, to varying extents, reduced fetal mobility, severe infantile hypotonia, childhood-onset obesity, hypogonadism, and intellectual disability. MAGEL2 mutations have been recently reported in affected individuals with features resembling PWS and called Schaaf-Yang syndrome. Here, we show that paternal MAGEL2 mutations are also responsible for lethal AMC, recapitulating the clinical spectrum of PWS and suggesting that MAGEL2 is a PWS-determining gene.
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KIAA0586, the human ortholog of chicken TALPID3, is a centrosomal protein that is essential for primary ciliogenesis. Its disruption in animal models causes defects attributed to abnormal hedgehog signaling; these defects include polydactyly and abnormal dorsoventral patterning of the neural tube. Here, we report homozygous mutations of KIAA0586 in four families affected by lethal ciliopathies ranging from a hydrolethalus phenotype to short-rib polydactyly. ⋯ Whereas centriolar maturation seemed unaffected in mutant cells, we observed an abnormal extended pattern of CEP290, a centriolar satellite protein previously associated with ciliopathies. Our data show the crucial role of KIAA0586 in human primary ciliogenesis and subsequent abnormal hedgehog signaling through abnormal GLI3 processing. Our results thus establish that KIAA0586 mutations cause lethal ciliopathies.