Col10a1 gene expression and chondrocyte hypertrophy during skeletal development and disease

Abstract

The type X collagen gene, COL10A1, is specifically expressed by hypertrophic chondrocytes during endochondral ossification. Endochondral ossification is a well-coordinated process that involves a cartilage intermediate and leads to formation of most of the skeleton in vertebrates during skeletogenesis. Chondrocyte hypertrophy is a critical stage of endochondral ossification linking both bone and cartilage development. Given its specific association with chondrocyte hypertrophy, type X collagen plays essential roles in endochondral ossification. It was previously shown that transgenic mice with mutant type X collagen develop variable skeleton-hematopoietic abnormalities indicating defective endochondral ossification, while mutations and abnormal expression of human COL10A1 cause abnormal chondrocyte hypertrophy that has been seen in many skeletal disorders, including skeletal chondrodysplasia and osteoarthritis. In this review, we summarized the skeletal chondrodysplasia with COL10A1 gene mutation that shows growth plate defect. We also reviewed recent studies that correlate the type X collagen gene expression and chondrocyte hypertrophy with osteoarthritis. Due to its significant clinical relevance, the type X collagen gene regulation has been extensively studied over the past two decades. Here, we focus on recent progress characterizing the cis-enhancer elements and their binding factors that together confer hypertrophic chondrocyte-specific murine type X collagen gene (Col10a1) expression. Based on literature review and our own studies, we surmise that there are multiple factors that contribute to hypertrophic chondrocyte-specific Col10a1 expression. These factors include both transactivators (such as Runx2, MEF2C etc.) and repressors (such as AP1, NFATc1, Sox9 etc.), while other co-factors or epigenetic control of Col10a1 expression may not be excluded.