Abstract

Purpose: Transformer2 proteins (Tra2? and Tra2?) control splicing patterns in human cells, and no human phenotypes have been associated with germline variants in these genes. The aim of this work was to associate germline variants in the TRA2B gene to a novel neurodevelopmental disorder. Methods: A total of 12 individuals from 11 unrelated families who harbored predicted loss-of-function monoallelic variants, mostly de novo, were recruited. RNA sequencing and western blot analyses of Tra2?-1 and Tra2?-3 isoforms from patient-derived cells were performed. Tra2?1-GFP, Tra2?3-GFP and CHEK1 exon 3 plasmids were transfected into HEK-293 cells. Results: All variants clustered in the 5? part of TRA2B, upstream of an alternative translation start site responsible for the expression of the noncanonical Tra2?-3 isoform. All affected individuals presented intellectual disability and/or developmental delay, frequently associated with infantile spasms, microcephaly, brain anomalies, autism spectrum disorder, feeding difficulties, and short stature. Experimental studies showed that these variants decreased the expression of the canonical Tra2?-1 isoform, whereas they increased the expression of the Tra2?-3 isoform, which is shorter and lacks the N-terminal RS1 domain. Increased expression of Tra2?-3-GFP were shown to interfere with the incorporation of CHEK1 exon 3 into its mature transcript, normally incorporated by Tra2?-1. Conclusion: Predicted loss-of-function variants clustered in the 5? portion of TRA2B cause a new neurodevelopmental syndrome through an apparently dominant negative disease mechanism involving the use of an alternative translation start site and the overexpression of a shorter, repressive Tra2? protein. © 2022 The Authors