Osteocrin (OSTN)

OSTN encodes a deduced mature protein of 133 amino acids with a predicted molecular mass of approximately 11.4 kD. The human and mouse OSTN proteins share 74% sequence identity. Both contain a signal peptide and 2 predicted cleavage sites, KKKR and KKR, which are similar to those found in peptide hormone precursors. OSTN is evolutionarily conserved, with highest sequence conservation at the C terminus. Immunofluorescence Mutagenesis experiments demonstrated that the 5-kD band results from cleavage at the KKKR site. Northern blot analysis of mouse tissues detected bone-specific Ostn expression, but RT-PCR detected very low expression in muscle, kidney, testis, and heart. mouse Ostn expression is highest in embryos and neonates, peaking at postnatal day 4 and decreasing steadily with age.