TEMPORAL EXPRESSION OF MYOGENIC REGULATORY GENES DURING ACTIVATION, PROLIFERATION, AND DIFFERENTIATION OF RAT SKELETAL-MUSCLE SATELLITE CELLS

The satellite cell is responsible for growth and repair of postnatal s keletal muscle. We investigated the expression of the myogenic regulat ory gene (MRG) family in these cells in the stages from quiescence to fusion. Using polymerase chain reaction amplification of reverse-trans cribed RNA (RT-PCR) isolated from adult rat satellite cells, we demons trated a temporal sequence of gene activation, which is distinct from that previously observed in embryonic semitic cells. No MRG expression was detected in predominantly quiescent cells. MyoD is activated by 1 2 h in cell culture, prior to the first evidence of proliferation. MRF 4 and myf-5 appear by 48 h and may be associated with the first divisi on cycle. Myogenin is not detectable until 72 h after satellite cell r ecovery from the muscle fiber, coincidental with the first evidence of differentiation. (C) 1994 Wiley-Liss, Inc.