Régulation de l'expression des gènes α et β de la tropomyosine au cours du développement du muscle pectoral chez le poulet

Abstract

Summary. Regulation of the expression of a and 13 tropomyosin genes in developing chicken pectoralis muscle.Accumulation of mRNAs coding for a and j3 skeletal tropomyosins was investigated using specific probes and normalized to muscle creatine kinase (M-CK) mRNA by slot-blot assays. In developing pectoralis muscle, the ratio of aTM messenger/M-CK remained constant until hatching, at which time the messenger disappeared within a week. However, in the leg, this ratio remained constant until 8 days after hatching, whereafter it decreased progressively to reach 30 % in the adult. The aTM/M-CK ratios were almost the same in the embryonic leg and pectoralis muscle. After hatching, there was a large increase in pectoralis muscle ( x 3 at day + 4, x 0 at day + 21 ) whereas, the increase was less pronounced and more progressive in the leg ( 3 3 at day 21 Run-on assays showed that nuclei isolated from 1 5-day in ovo leg and pectoralis muscles had similar patterns of muscle specific gene transcription whereas post-hatched pectoralis muscle nuclei were shown to have a higher rate of a to j3 tropomyosin gene transcription. These data are in accordance with the results obtained for protein analysis of leg and pectoralis muscles and support the notion that changes in the protein pattern of developing muscle can be relevant to coordinate regulation of gene transcription.Introduction.