WDR83OS (also known as Asterix) is a component of the multi-pass translocon (MPT) complex that facilitates insertion of multi-spanning membrane proteins into the endoplasmic reticulum (ER) membrane 1. Within the MPT complex, WDR83OS heterodimerizes with CCDC47 to form the PAT (protein associated with ER translocon) subcomplex, which functions as an intramembrane chaperone 21. The PAT complex engages nascent transmembrane domains (TMDs) containing hydrophilic residues and protects them from the non-polar membrane environment during co-translational protein biogenesis, disengaging upon substrate folding 1. WDR83OS also interacts with multipass transmembrane proteins including TRPC6 and participates in signal recognition particle-independent protein-targeting pathways 3. Biallelic loss-of-function variants in WDR83OS cause a neurodevelopmental disorder characterized by neurodevelopmental delay, facial dysmorphism, and hypercholanemia (elevated bile acids) 24. Affected individuals consistently present with intellectual disability and intractable itching, while liver enzymes typically remain normal despite elevated bile acids 2. Zebrafish studies support WDR83OS's critical role in nervous system and craniofacial development 2. The specific mechanism linking WDR83OS dysfunction to cholestasis remains incompletely understood, though WDR83OS interacts with known bile homeostasis regulators.