Clinical relevance of postzygotic mosaicism in Cornelia de Lange syndrome and purifying selection of NIPBL variants in blood.
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2021
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Scientific Reports
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Abstract
Postzygotic mosaicism (PZM) in NIPBL is a strong source of causality for Cornelia de Lange syndrome
(CdLS) that can have major clinical implications. Here, we further delineate the role of somatic
mosaicism in CdLS by describing a series of 11 unreported patients with mosaic disease-causing
variants in NIPBL and performing a retrospective cohort study from a Spanish CdLS diagnostic
center. By reviewing the literature and combining our findings with previously published data, we
demonstrate a negative selection against somatic deleterious NIPBL variants in blood. Furthermore,
the analysis of all reported cases indicates an unusual high prevalence of mosaicism in CdLS,
occurring in 13.1% of patients with a positive molecular diagnosis. It is worth noting that most of
the affected individuals with mosaicism have a clinical phenotype at least as severe as those with
constitutive pathogenic variants. However, the type of genetic change does not vary between
germline and somatic events and, even in the presence of mosaicism, missense substitutions are
located preferentially within the HEAT repeat domain of NIPBL. In conclusion, the high prevalence
of mosaicism in CdLS as well as the disparity in tissue distribution provide a novel orientation for the
clinical management and genetic counselling of families.