Linkage-specific deubiquitylation by OTUD5 defines an embryonic pathway intolerant to genomic variation [RNA-Seq]

Reversible modification of proteins with linkage-specific ubiquitin chains is critical for intracellular signaling. Yet, information on physiological roles and underlying signaling mechanisms of particular ubiquitin linkages during human development are limited. Here, relying on genomic constraint scores, we identify 10 patients with a novel multiple congenital anomaly disorder caused by hemizygous variants in OTUD5, encoding a K48-/K63-linkage-specific deubiquitylase. By studying these mutations, we find that OTUD5 controls neuroectodermal differentiation through cleaving K48-linked ubiquitin chains to counteract degradation of a select group of chromatin regulators. These include ARID1A/B, HDAC2, and HCF1, mutation of which underlie different developmental disorders that exhibit phenotypic overlap with OTUD5 patients. Consequently, loss of OTUD5 during early differentiation leads to less accessible chromatin at neuroectodermal enhancers and thus aberrant rewiring of gene expression networks. Our study describes a novel developmental disorder we name LINKED (LINKage-specific-deubiquitylation-deficiency-induced Embryonic Defects) syndrome, provides a previously unrecognized mechanistic link between phenotypically related diseases, and reveals linkage-specific ubiquitin cleavage from substrate groups (i.e. chromatin remodelers) as an essential mode of signaling required to coordinate embryonic differentiation pathways. Overall design: RNA-seq was performed in human stem cells and following three days of neural differentiation. Cells treated with control shRNA were compared against cells treated with shRNA targeting OTUD5. Each condition/timepoint was performed in triplicate.