APXL is a 1,616 amino acid protein that localizes to a variety of locations within the cell, including the cytoplasm, the cytoskeleton, the cell junction and the apical cell membrane. Containing one ASD1 domain, one ASD2 domain and one PDZ domain, APXL interacts with F-Actin and is thought to mediate endothelial cell morphology during cell spreading, possibly regulating melanosome biogenesis and inducing γ Tubulin redistribution. APXL is expressed in kidney, brain, lung, pancreas and placenta and is overexpressed in melanomas, suggesting a role in tumor transformation and metastasis. The gene encoding APXL maps to human chromosome X, which contains nearly 153 million base pairs and houses over 1,000 genes. In conjunction with chromosome Y, chromosome X is responsible for sex determination. There are a number of conditions related to an abnormal number and combination of sex chromosomes, some of which include Turner's syndrome, color blindness, hemophilia and Duchenne muscular dystrophy.