Clinical exome sequencing reveals locus heterogeneity and phenotypic variability of cohesinopathies
2019
Defects in the
cohesinpathway are associated with cohesinopathies, notably
Cornelia de Lange syndrome(CdLS). We aimed to delineate pathogenic variants in known and candidate cohesinopathy genes from a clinical
exomeperspective. We retrospectively studied patients referred for clinical
exome sequencing(CES, N = 10,698). Patients with causative variants in novel or recently described cohesinopathy genes were enrolled for phenotypic characterization. Pathogenic or likely pathogenic single-nucleotide and insertion/deletion variants (SNVs/
indels) were identified in established disease genes including
NIPBL(N = 5),
SMC1A(N = 14), SMC3 (N = 4), RAD21 (N = 2), and
HDAC8(N = 8). The phenotypes in this genetically defined cohort skew towards the mild end of CdLS spectrum as compared with phenotype-driven cohorts. Candidate or recently reported cohesinopathy genes were supported by de novo SNVs/
indelsin STAG1 (N = 3), STAG2 (N = 5), PDS5A (N = 1), and WAPL (N = 1), and one inherited SNV in PDS5A. We also identified copy-number deletions affecting STAG1 (two de novo, one of unknown inheritance) and STAG2 (one of unknown inheritance). Patients with STAG1 and STAG2 variants presented with overlapping features yet without characteristic facial features of CdLS. CES effectively identified disease-causing alleles at the mild end of the cohensinopathy spectrum and enabled characterization of candidate disease genes.
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