A novel gene, tendin, is strongly expressed in tendons and ligaments and shows high homology with chondromodulin-I

Chondromodulin-I (CHM1) was identified recently as an angiogenesis inhibito r in cartilage. It is highly expressed in the avascular zones of cartilage but is absent in the late hypertrophic region, which is invaded by blood ve ssels during enchondral ossification. Blast searches with the C-terminal pa rt of CHM1 in available databases led to the identification of human and mo use cDNAs encoding a new protein, Tendin, that shares high homology with CH M1, Based on computer predictions, Tendin is a type II transmembrane protei n containing a putative proteinase cleavage and two glycosylation sites. No rthern assays with mouse RNAs demonstrated strong expression of a 1.5-kb te ndin transcript in the diaphragm, skeletal muscle, and the eye and low leve ls of expression in all other tissues investigated. In 17.5-day-old mouse e mbryos, in situ hybridization revealed high levels of tendin transcript in tendons and ligaments. Additional signals were detected in brain and spinal cord, liver, lung, bowels, thymus, and eye. Cartilage, where CHM1 is found , revealed low levels of tendin m-RNA. In adult mice, tendin is expressed i n neurons of all brain regions and the spinal cord. The tendin gene is loca lized in the human Xq22 region, to which several human diseases have been m apped. (C) 2001 Wiley-Liss, Inc.