WASHC1 encodes a core component of the WASH complex, a nucleation-promoting factor that recruits and activates the Arp2/3 complex to generate branched actin filaments at endosomal membranes 1. The primary function involves endosomal tubule fission during cargo sorting and recycling of transmembrane receptors including the LDL receptor, scavenger receptor B type I, and T-cell receptors 2. WASHC1 facilitates cholesterol homeostasis by regulating hepatic LDL and HDL clearance; hepatic WASHC1 ablation elevates plasma cholesterol and reduces surface expression of lipid receptors 2. Intestinal WASHC1 deficiency impairs cholesterol absorption and alters bile acid composition, indicating WASHC1's role in lipid metabolism across tissues 3. Beyond endosomal trafficking, nuclear WASHC1 promotes cell survival under replication stress by facilitating MCM2-7 complex loading at DNA replication origins, maintaining chr9 stability 4. WASHC1 also negatively regulates autophagy and coordinates exocytosis of matrix metalloproteinase-14 during invasive cell migration. Recent genomic analysis reveals functional complexity: while WASHC1 on chromosome 9 was historically considered the primary WASH1 gene, LOC124908094 on chromosome 9 appears to be the predominant functional WASH1 coding gene, with WASHC1 potentially being a pseudogene 56. Clinical relevance includes associations with developmental and neurological disorders through WASH complex dysfunction.