A novel mouse gene highly conserved throughout evolution: regulation in adipocyte differentiation and in tumorigenic cell lines.

A cDNA clone referred to as 168 was previously isolated from mouse 1246 adipocytes by differential hybridization on the basis of its down regulation in adipocytes when compared to preadipocytes. 5' RACE was used to obtain a full length clone of 761 bp encoding for a highly basic 25 kD polypeptide that is extremely conserved in several diverse species of eukaryotes. There is a single amino acid substitution at position 202 compared to the human homolog, QM, a putative tumor suppressor. Clone 168 mRNA decreases 80% in rat primary culture of adipocytes compared to preadipocytes and does not decrease when differentiation is blocked by PGF2 alpha or EGF, indicating that the decrease is correlated with expression of the differentiation phenotype. Finally, two 1246 cell line variants that exhibit altered growth and increased tumorigenicity have a similar level of 168 mRNA when compared to the non tumorigenic adipogenic parent cell line.