Clinical, in vitro, and in vivo evidence of WAPL as a cohesinopathy-associated gene and phenotypic driver of 10q22.3q23.2 genomic disorder

Cohesin orchestrates gene expression via three-dimensional chromosome folding. Genes encoding cohesin and cohesin loaders have been associated with Mendelian disorders, whereas genes encoding cohesin release factors, including WAPL and its binding partners PDS5A and PDS5B, have not. We explored the relevance of cohesin release factors in Mendelian disease by phenotyping individuals with heterozygous predicted damaging variants in WAPL ( n = 27), PDS5A ( n = 8), and PDS5B ( n = 8), by modeling WAPL deficiency in human cells and mice, and by aggregating disease association statistics from consortia studies. We identified a WAPL -related disorder featuring developmental delay, intellectual disability, and risk of other developmental anomalies. Similarities between individuals with damaging WAPL variants and those with large, recurrent 10q22.3q23.2 (10q) deletions encompassing WAPL nominate WAPL as a driver gene within this genomic disorder region. While individuals with PDS5A or PDS5B variants exhibited features of developmental disorders, neither cohort-based statistics nor subject phenotyping associated these genes with specific phenotypes. We used CRISPR to generate truncating variants in WAPL and 10q deletion or duplication in human induced pluripotent stem cells (iPSCs) and induced neurons. Transcriptomics identified significant overlap between WAPL haploinsufficiency and 10q deletion differentially expressed genes. Mice with 50% Wapl expression exhibited mild deficits of growth and learning/memory, whereas those with 25% residual Wapl displayed birth defects and postnatal lethality, revealing a dosage liability threshold below the level of heterozygosity. In summary, we delineated a genetic condition caused by cohesin release factor deficiency, nominated WAPL as a driver gene within a genomic disorder region, and further illuminated dosage sensitivity of human cohesin.