Receptor-type tyrosine-protein phosphatase delta is an enzyme that is encoded by the PTPRD gene. The protein encoded by this gene is a member of the protein tyrosine phosphatase (PTP) family. PTPs are known to be signaling molecules that regulate a variety of cellular processes including cell growth, differentiation, mitotic cycle, and oncogenic transformation. PTPRD has been shown to interact with PTPRS and liprin-alpha-1. Studies of the similar genes in chick and fly suggest the role of this PTP is in promoting neurite growth, and regulating neurons axon guidance. Multiple tissue specific alternatively spliced transcript variants of this gene have been reported. Mutations in the PTPRD gene are associated with autism, obsessive–compulsive disorder, and breast cancer.