SCUBE3 is a novel secreted 993 amino acid cell-surface osteoblast protein that plays an important role in bone cell biology. While highly expressed in osteoblasts, SCUBE3 expression is unobservable or very low in non-bone tissues. SCUBE3 forms homo-oligomers and hetero-oligomers with SCUBE1, and may undergo C-terminal proteolytic cleavage or become N-glycosylated following translation. Two SCUBE3 isoforms exist as a result of alternative splicing events. SCUBE3 contains one CUB domain and nine EGF-like domains, and is encoded by a gene which maps to human chromosome 6p21.31, a region associated with a rare form of metabolic bone disease known as Paget's disease. Chromosome 6 contains 170 million base pairs and comprises nearly 6% of the human genome.