PTCHD3 is a 767 amino acid multi-pass membrane protein that localizes to the midpiece of the sperm tail, where it is implicated in sperm function and development. A member of the patched family, PTCHD3 contains one SSD (sterol-sensing) domain and is encoded by a gene that maps to human chromosome 10p12.1. Spanning nearly 135 million base pairs, chromosome 10 makes up approximately 4.5% of total DNA in cells and encodes nearly 1,200 genes. Several protein-coding genes, including those that encode for chemokines, cadherins, excision repair proteins, early growth response factors (Egrs) and fibroblast growth receptors (FGFRs), are located on chromosome 10. Defects in some of the genes that map to chromosome 10 are associated with Charcot-Marie Tooth disease, Jackson-Weiss syndrome, Usher syndrome, nonsyndromatic deafness, Wolman??s syndrome, Cowden syndrome, multiple endocrine neoplasia type 2 and porphyria.