gas2 is a multifunctional gene involved in the regulation of apoptosis andchondrogenesis in the developing mouse limb

The growth-arrest-specific 2 (gas2) gene was initially identified on accoun t of its high level of expression in murine fibroblasts under growth arrest conditions, followed by downregulation upon reentry into the cell cycle (S chneider et al,, Cell 54, 787-793, 1988), In this study, the expression pat terns of the gas2 gene and the Gas2 peptide were established in the develop ing limbs of 11.5- to 14.5-day mouse embryos. It was found that gas2 was ex pressed in the interdigital tissues, the chondrogenic regions, and the myog enic regions, Low-density limb culture and Brdu incorporation assays reveal ed that gas2 might play an important role in regulating chondrocyte prolife ration and differentiation. Moreover, it might play a similar role during l imb myogenesis. In addition to chondrogenesis and myogeneis, gase is involv ed in the execution of the apoptotic program in hindlimb interdigital tissu es-by acting as a death substrate for caspase enzymes. TUNEL analysis demon strated that the interdigital tissues underwent apoptosis between 13.5 and 15.5 days. Exactly at these time points, the C-terminal domain of the Gas2 peptide was cleaved as revealed by Western blot analysis. Moreover, pro-cas pase-3 tan enzyme that can process Gas2) was cleaved into its active form i n the interdigital tissues. The addition of zVAD-fmk, a caspase enzyme inhi bitor, to 12.5-day-old hindlimbs maintained in organ culture revealed that the treatment inhibited interdigital cell death. This inhibition correlated with the absence of the Gas2 peptide and pro-caspase-3 cleavage. The data suggest that Gase might be involved in the execution of the apoptotic proce ss. (C) 1999 Academic Press.