A homozygous humanWNT11loss-of-function variant associated with laterality, heart and renal defects

Wnt signaling plays important roles during vertebrate development, including left-right axis specification as well as heart and kidney organogenesis. We identified a homozygous human WNT11 variant in an infant with Situs inversus totalis , complex heart defects and renal hypodysplasia, and we used Xenopus embryos to functionally characterize this variant. WNT11 c.814delG encodes a loss-of-function protein with reduced stability that lost signaling activity in vivo . This is remarkable, because the variant encodes a truncated ligand with nearly identical length and predicted structure to dominant-negative Wnts. Furthermore, we demonstrate that alteration of the truncated C-terminal end can restore stability and dominant-negative signaling activity. Our study also suggests similar functions for WNT11 in human development as described in model organisms. Therefore, biallelic WNT11 dysfunction should be considered as novel genetic cause in syndromal human phenotypes presenting with congenital heart defects and renal hypoplasia, with or without laterality defects. The work presented here enhances our understanding of human development and structure-function relationships in Wnt ligands.