Zinc Finger Protein Zac1 Is Expressed in Chondrogenic Sites of the Mouse

Zac1 is a zinc finger transcription factor that elicits antiproliferative activity and is a potential tumor suppressor gene. Through a detailed spatiotemporal study by in situ hybridization of mouse embryos, we have found that Zac1 transcript is predominantly localized in developing chondrogenic tissue, in addition to the central nervous system as reported elsewhere. Zac1 is also expressed transiently in the myocardium, skeletal muscle, and basal aspect of the stratified embryonic epithelia. During cartilage development, the pattern of Zac1 expression is in close accordance with the distribution of type II collagen mRNA in mesenchymal condensation and prehypertrophic chondrocytes. In mouse ATDC5 cells undergoing in vitro chondrogenesis, the Zac1 mRNA is up-regulated in parallel with genes expressed in precartilage but the Zac1 expression is low when type II collagen mRNA is markedly increased in differentiated cells. Together, these results suggest that Zac1 is a potential regulatory gene involved in chondrogenic differentiation.