SOX9 in Organogenesis: Shared and Unique Transcriptional Functions

The document discusses the role of the protein SOX9 in organogenesis, or the formation of organs during embryonic development. SOX9 is crucial in the development of various organs including cartilage, testis, and hair follicle. It is involved in chondrocyte differentiation and proliferation in cartilage, Sertoli cell differentiation and testis determination, and the survival of mesenchymal cells and chondrocytes. SOX9 also plays a role in the development of the nervous system, retina, lung, heart valve, pancreas, bile duct, intestine, and prostate. In hair follicles, SOX9 is expressed in hair follicle stem cells and is involved in hair follicle morphogenesis and cycling. It is crucial for matrix cell proliferation and the maintenance of hair follicle stem cells. When SOX9 is removed, it leads to impaired proliferative capacity in the matrix cells, loss of the hair follicle stem cell marker CD34, and loss of external hair.