THE ZONAL EXPRESSION OF CHICKEN CARTILAGE MATRIX PROTEIN GENE IN THE DEVELOPING SKELETON OF TRANSGENIC MICE

Cartilage matrix protein (CMP) is a major noncollagenous glycoprotein of hyaline cartilage with a molecular mass of about 148 kDa. It has be en proposed to be involved in matrix organization by its interactions with proteoglycan and type II collagen. The 54-kDa monomers form homot rimers stabilized by disulfide bonds. The gene for chicken cartilage m atrix protein was isolated, and its regulation has been studied recent ly in transient expression experiments. To learn more about the spatia l and temporal expression of the gene during ontogenic development, we created transgenic mice via microinjection of a 21.8-kb genomic fragm ent, encoding the chicken cartilage matrix protein. None of the founde r animals exhibited any abnormal phenotype. The developmental stage-sp ecific expression of the transgene was examined by immunostaining with a chicken CMP specific antiserum at different stages of embryonic dev elopment in cartilage from different sources: lower and upper limb, ve rtebrae, ribs and nasal septum. The level of transgene expression show ed marked differences in various zones of cartilage. Briefly, high lev els were found in the zones of proliferating chondrocytes, while littl e if any transgene product was detected in the very early and hypertro phic stage of chondrogenesis. The expression pattern of the transgene correlated with the endogenous mouse CMP and did not cause any morphol ogical changes detectable by microscopic analysis of cartilage. These data indicate that the injected CMP gene with its flanking sequences c ontained all the information necessary for cell type-specific expressi on in transgenic mice.