Many proteins containing ZP (zona pellucida) domains play fundamental roles in development, immunity, hearing and cancer. These domains are located near the carboxy-terminus of the polypeptide and typically consist of approximately 260 amino acids. ZP domain-containing proteins are often glycosylated and are usually present in filaments or matrices and therefore are thought to be involved in protein polymerization. ZPLD1 (Zona pellucida-like domain-containing protein 1) is a 415 amino acid single-pass transmembrane protein that contains one ZP domain. The gene encoding ZPLD1 maps to human chromosome 3, which is made up of about 214 million bases encoding over 1,100 genes, including a chemokine receptor (CKR) gene cluster and a variety of human cancer-related gene loci. There are two isoforms of ZPLD1 that are produced as a result of alternative splicing events.