Somatic and de novo Germline Variants of MEDs in Human Neural Tube Defects

Abstract

BackgroundNeural tube defects (NTDs) are among the most common and severe congenital defects in humans. Their genetic etiology is complex and remains poorly understood. The Mediator complex (MED) plays a vital role in neural tube development in animal models. However, no studies have yet examined the role of its human homolog in the etiology of NTDs.MethodsIn this study, 48 pairs of neural lesion site and umbilical cord tissues from NTD and 21 case-parent trios were involved in screening for NTD-related somatic and germlinede novovariants. A series of functional cell assays were performed. We generated aMed12p.Arg1784Cys knock-in mouse using CRISPR/Cas9 technology to validate the human findings.ResultsOne somatic variant,MED12p.Arg1782Cys, was identified in the lesion site tissue from an NTD fetus. This variant was absent in any other normal tissue from different germ layers of the same case. In 21 case-parent trios, onede novostop-gain variant,MED13Lp.Arg1760∗, was identified. Cellular functional studies showed thatMED12p.Arg1782Cys decreased MED12 protein level and affected the regulation ofMED12on the canonical-WNT signaling pathway. TheMed12p.Arg1784Cys knock-in mouse exhibited exencephaly and spina bifida.ConclusionThese findings provide strong evidence that functional variants ofMEDgenes are associated with the etiology of some NTDs. We demonstrated a potentially important role for somatic variants in the occurrence of NTDs. Our study is the first study in which an NTD-related variant identified in humans was validated in mice using CRISPR/Cas9 technology.