Investigation of molecular etiopathogenesis of syndromes with contractures in fetal period by next generation sequencing methods

Multiple congenital contractures (MCC), alternatively referred to as arthrogryposis multiplex congenita, is a phenotypic descriptor implying congenital contractures in two or more body areas. Whole exome sequencing (WES) provides an effective approach for elucidating the molecular basis, considering the presence of genetic and phenotypic heterogeneity. We aimed to identify the molecular etiology in fetuses within the lethal MCC spectrum, using WES. 15 patients from 11 families displaying MCC were enrolled. WES analysis was performed in 11 index cases that had normal array-CGH results. Sanger sequencing was performed for validation and segregation of the variants. Eight families were shown to harbor known or novel candidate variants in COG6, NEB, RAPSN, KIAA1109, DOK7, HSPG2, and PSAT1. Three patients manifested with blended phenotypes, harboring additional biallelic variants in VPS13B, DNAH9, and USH2A. Moreover, we identified a frameshift variant in USP14 in three similarly affected fetuses. The resemblance of the fetal findings to the previously reported Usp14-/- mouse models and RT-qPCR performed in our study supported that the variant likely led to a novel human MCC phenotype. Overall, molecular etiology was determined in 81.8% of the cohort using WES analysis. This is the first MCC cohort study conducted entirely on fetuses. Our results provide new insights into the clinical and molecular spectrum of lethal MCC phenotypes, expand the genotype-phenotype correlations, and present the first human phenotype that appears to be attributable to a truncating variant in USP14.