THE FUNCTION OF HMG-BOX TRANSCRIPTION FACTORS Sox4a AND Sox4b IN ZEBRAFISH BONE DEVELOPMENT AND HOMEOSTASIS.

In mammals, the Sox4 gene is involved in development of endocardial crests, the brain, the lung, teeth, gonads and lymphocytes. Recently, Sox4 was shown to control bone mass and mineralization in mice. In zebrafish, two homologs for the mammalian Sox4 are present, sox4a and sox4b. Here we investigate the function of the sox4a and sox4b genes in cartilage and bone development in zebrafish. Therefore, we focus our attention on the first bone structures to be formed, the head skeleton and more precisely the pharyngeal cartilage. We show that both genes are expressed in the pharyngeal region, albeit at different time points during development. Double in situ hybridization experiments are used to exactly define the particular tissues where they are expressed. Furthermore, microinjection experiments of antisense oligonucleotides are used to block translation of these specific genes and to define their precise function during cartilage and bone development.