ACETYLCHOLINE-RECEPTOR AND MYOGENIC FACTOR GENE-EXPRESSION IN TORPEDOEMBRYONIC-DEVELOPMENT

THE mRNA levels of acetylcholine receptor (AChR) and myogenic factors were followed during embryonic development of Torpedo skeletal muscle and its homologue, the electric organ. A different developmental patte rn of AChR gene expression was found in these two tissues: a slight de crease in the muscle, and a marked increase, concomitant with synapse formation, in the electric organ. However, the developmental pattern o f MyoD and MRF4 mRNA levels was similar in both tissues, with no signi ficant changes during development. This is in contrast with the sharp increase in the expression of AChR in the electric organ and may sugge st that the burst in the expression of AChR during the differentiation of myotubes into electrocytes is not regulated by changes in the myog enic factor mRNA levels.