WASHC1 encodes a core component of the WASH complex, a pentameric protein that functions as a nucleation-promoting factor at endosomal membranes 1. The WASH complex recruits and activates the Arp2/3 complex to generate branched actin filaments, driving tubule fission during endosomal cargo sorting and the recycling of transmembrane receptors including the LDL receptor, transferrin receptor, and T-cell receptors to the plasma membrane. In addition to endosomal trafficking, WASHC1 localizes to the nucleus where it interacts with DNA replication machinery, promoting cell survival under replication stress 2. Clinically, WASHC1 dysfunction impairs lipid homeostasis: hepatic WASHC1 ablation increases plasma LDL and HDL cholesterol by reducing surface expression of LDL receptor and scavenger receptor class B type I 3, while intestinal WASHC1 loss decreases cholesterol absorption and increases fecal sterol loss 4. WASHC1 is also implicated in T-cell immune synapse assembly and neurotrophic receptor trafficking in neurons 56. Notably, recent genomic studies indicate that the functional WASH1 protein may be primarily produced by LOC124908094 rather than the annotated WASHC1 gene on chromosome 9, though WASHC1 remains widely studied in disease contexts.