EXPRESSION OF GROWTH ARREST-SPECIFIC (GAS) GENES IN MURINE KERATINOCYTES - GAS2 IS SPECIFICALLY REGULATED

In order to elucidate a possible role of growth arrest-specific (gas) genes in the regulation of tissue proliferation, we analyzed their exp ression in keratinocytes isolated from murine back skin. On the mRNA l evel gas1, gas5, and gas6 were found to be significantly expressed whe reas there was a relatively low expression of gas2, gas3, and gas4. Us ing keratinocytes fractionated according to their density resulted in subpopulations of cells: differentiating suprabasal cells in fractions I and II; proliferative basal cells in fractions ma, III and IV. We f ound gas2 protein to be expressed more strongly in the proliferative c ells than in the differentiating cells. Stimulation of hyperproliferat ion by 12-O-tetradecanoylphorbol-13-acetate (TPA) resulted in a transi ent increase of gas2 protein content concomitantly with the time of ma ximal cell renewal. In this respect the murine keratinocyte cell line MSCP5 resembled freshly isolated keratinocytes. There was a higher exp ression of gas2 protein during exponential growth than during growth a rrest, induced either by serum starvation or by TGF beta treatment. Si nce, in contrast to the results reported for 3T3 cells, growth arrest within these cells was not accompanied by an elevation of gas2 protein , we suggest a cell-specific regulation of its expression. (C) 1996 Ac ademic Press, Inc.