PROOPIOMELANOCORTIN GENE IS EXPRESSED IN POSTIMPLANTATION MOUSE EMBRYOS AND ENHANCES GROWTH-POTENTIAL OF MYOGENIC CELLS

We previously showed that the adrenocorticotropin hormone (ACTH) is a mitogen for myoblasts and is present in post-implantation mammalian em bryos (Cossu et al. [1989] Dev. Biol. 131:331-336; De Angelis et al. [ 1992] Dev. Biol. 151:446-458). In this paper, we investigated the expr ession of the corresponding gene, pro-opiomelanocortin (POMC), by in s itu hybridization and polymerase chain reaction. In situ analysis reve aled low level expression in the basal layer of 10.5 d.p.c. neural tub e and in several discrete areas around the dorsal aorta. By more sensi tive Reverse-transcription polymerase chain reaction (RT-PCR) analysis , expression was detected also in developing limb buds and in cultured myogenic cells, but not in fibroblasts. To investigate the possible r ole of POMC gene expression in myogenesis, we induced its over-express ion in proliferating myoblasts. Upon sub-optimal growth conditions, ov er-expressing cells were found to give rise to clones larger than cont rol cells. The differentiation potential of POMC over-expressing myoge nic cells was unchanged. (C) 1993 Wiley-Liss, Inc.