Muskelin is a 735 amino acid nuclear and cytoplasmic protein that mediates cytoskeletal responses and cell spreading to Thrombospondin 1, an extracellular matrix glycoprotein. Forming a CTLH complex with RMND5A, Ran BP-M and TWA1, Muskelin exists as two alternatively spliced isoforms. Muskelin is implicated as an isoform-specific anchoring protein for the prostaglandin EP3 receptor, and contains one LisH domain, a CTLH domain, six Kelch repeats and an N-terminal discoidin-like domain through which it self-associates via a head-to-tail mechanism. Human and mouse Muskelin share 98% amino acid seqeuence homology and are encoded by genes located on chromosomes 7q32.3 and 6 A3.3, respectively.