Osteocrin

Using single-sequence trap methods, two different groups identified the same peptide with similarity to natriuretic peptides from the bone in 2003 (named OSTN), and from the muscle in 2004 (named musclin).

The human OSTN gene (OSTN) is located on chromosome 3 (3q28) while ANP (NPPA)/BNP (NPPB) (1p36) and CNP (NPPC) (2q37) are located on different chromosomes. The human OSTN mRNA is 3231bp (402bp coding sequence). Like BNP mRNA, repetitive AUUUA motifs in the 30-untranslated region are present in humans and Xenopus OSTN mRNAs. However, some species, including mice, chickens, and zebrafish, do not possess this motif.

Although OSTN was originally found to inhibit osteoblast activity in vitro,the main action of OSTN is blocking the clearance activity of NPR-C. The effect increases the circulating CNP level and reinforces CNP/NPR-B binding.Therefore, OSTN is thought to be amodulator of circulating CNP.OSTN expresses in the muscle, which may act as a myokine.However, the target cells are unknown.

OSTN contains two natriuretic peptide motifs, and is expressed mainly in the bones and muscle. It is thought to be an endogenous specific ligand for the clearance natriuretic peptide receptor (NPR-C) and to modulate CNP levels by blocking NPR-C activity.