MOLECULAR-CLONING, CHARACTERIZATION, AND GENETIC-MAPPING OF THE CDNA CODING FOR A NOVEL SECRETORY PROTEIN OF MOUSE - DEMONSTRATION OF ALTERNATIVE SPLICING IN SKIN AND CARTILAGE

A novel 85-kDa protein secreted by the mouse stromal osteogenic cell l ine MN7 was identified using two-dimensional polyacrylamide gel electr ophoresis (Mathieu, E., Meheus, L., Raymackers, J., and Merregaert, J. (1994) J. Bone Miner. Res. 9, 903-913). Degenerate primers were used to isolate the cDNA coding for this protein, The full-length cDNA clon e is 1.9 kilobases (kb) and codes for a protein of 559 amino acid resi dues, The DNA and deduced amino acid sequences have no counterparts in public data bases, but a structural similarity involving typical cyst eine doublets can be observed to serum albumin family proteins and to Endo16 (a calcium-binding protein of sea urchin), Northern blot analys is revealed the presence of a 1.9-kb transcript in various tissues, an d a shorter transcript of 1.5 kb, derived by alternative splicing in t ail, front paw and skin of embryonic mice. The gene for the p85 protei n, termed Ecm1 (for extracellular matrix protein 1), is a single-copy gene, which was localized to the region on mouse chromosome 3 known to contain at least one locus associated with developmental disorders of the skin, soft coat (soc), Alternative splicing may serve as a mechan ism for generating functional diversity in the Ecm1 gene.