👤 Hanan E Shamseldin

There is a growing interest in standardizing gene-disease associations for the purpose of facilitating the proper classification of variants in the context of Mendelian diseases. One key line of evidence is the independent observation of pathogenic variants in unrelated individuals with similar phenotypes. Here, we expand on our previous effort to exploit the power of autozygosity to produce homozygous pathogenic variants that are otherwise very difficult to encounter in the homozygous state due to their rarity. The identification of such variants in genes with only tentative associations to Mendelian diseases can add to the existing evidence when observed in the context of compatible phenotypes. In this study, we report 20 homozygous variants in 18 genes ( Show less

PurposeThe application of genomic sequencing to investigate unexplained death during early human development, a form of lethality likely enriched for severe Mendelian disorders, has been limited.MethodsIn this study, we employed exome sequencing as a molecular autopsy tool in a cohort of 44 families with at least one death or lethal fetal malformation at any stage of in utero development. Where no DNA was available from the fetus, we performed molecular autopsy by proxy, i.e., through parental testing.ResultsPathogenic or likely pathogenic variants were identified in 22 families (50%), and variants of unknown significance were identified in further 15 families (34%). These variants were in genes known to cause embryonic or perinatal lethality (ALPL, GUSB, SLC17A5, MRPS16, THSD1, PIEZO1, and CTSA), genes known to cause Mendelian phenotypes that do not typically include embryonic lethality (INVS, FKTN, MYBPC3, COL11A2, KRIT1, ASCC1, NEB, LZTR1, TTC21B, AGT, KLHL41, GFPT1, and WDR81) and genes with no established links to human disease that we propose as novel candidates supported by embryonic lethality of their orthologs or other lines of evidence (MS4A7, SERPINA11, FCRL4, MYBPHL, PRPF19, VPS13D, KIAA1109, MOCS3, SVOPL, FEN1, HSPB11, KIF19, and EXOC3L2).ConclusionOur results suggest that molecular autopsy in pregnancy losses is a practical and high-yield alternative to traditional autopsy, and an opportunity for bringing precision medicine to the clinical practice of perinatology. Show less

Brain channelopathies represent a growing class of brain disorders that usually result in paroxysmal disorders, although their role in other neurological phenotypes, including the recently described NALCN-related infantile encephalopathy, is increasingly recognized. In three Saudi Arabian families and one Egyptian family all affected by a remarkably similar phenotype (infantile encephalopathy and largely normal brain MRI) to that of NALCN-related infantile encephalopathy, we identified a locus on 2q34 in which whole-exome sequencing revealed three, including two apparently loss-of-function, recessive mutations in UNC80. UNC80 encodes a large protein that is necessary for the stability and function of NALCN and for bridging NALCN to UNC79 to form a functional complex. Our results expand the clinical relevance of the UNC79-UNC80-NALCN channel complex. Show less

Dysmorphology syndromes are among the most common referrals to clinical genetics specialists. Inability to match the dysmorphology pattern to a known syndrome can pose a major diagnostic challenge. With an aim to accelerate the establishment of new syndromes and their genetic etiology, we describe our experience with multiplex consanguineous families that appeared to represent novel autosomal recessive dysmorphology syndromes at the time of evaluation. Combined autozygome/exome analysis of multiplex consanguineous families with apparently novel dysmorphology syndromes. Consistent with the apparent novelty of the phenotypes, our analysis revealed a strong candidate variant in genes that were novel at the time of the analysis in the majority of cases, and 10 of these genes are published here for the first time as novel candidates (CDK9, NEK9, ZNF668, TTC28, MBL2, CADPS, CACNA1H, HYAL2, CTU2, and C3ORF17). A significant minority of the phenotypes (6/31, 19%), however, were caused by genes known to cause Mendelian phenotypes, thus expanding the phenotypic spectrum of the diseases linked to these genes. The conspicuous inheritance pattern and the highly specific phenotypes appear to have contributed to the high yield (90%) of plausible molecular diagnoses in our study cohort. Reporting detailed clinical and genomic analysis of a large series of apparently novel dysmorphology syndromes will likely lead to a trend to accelerate the establishment of novel syndromes and their underlying genes through open exchange of data for the benefit of patients, their families, health-care providers, and the research community.Genet Med 18 7, 686-695. Show less