DIFFERENTIAL EXPRESSION OF C-PROTEIN ISOFORMS IN THE DEVELOPING HEARTOF NORMAL AND CARDIAC LETHAL MUTANT AXOLOTLS (AMBYSTOMA-MEXICANUM)

Regulated assembly of contractile proteins into sarcomeric structures, such as A- and I-bands, is still currently being defined. The presenc e of distinct isoforms of several muscle proteins suggests a possible mechanism by which myocytes regulate assembly during myofibrillogenesi s. Of several muscle isoforms located within the A-band, myosin bindin g proteins (MyBP) are reported to be involved in the regulation and st abilization of thick filaments during sarcomere assembly. The present confocal study characterizes the expression of one of these myosin bin ding proteins, C-protein (MyBP-C) in wild-type and cardiac lethal muta nt embryos of the axolotl, Ambystoma mexicanum. C-protein isoforms are also detected in distinct temporal patterns in whole-mounted heart tu bes and thoracic skeletal muscles. Confocal analysis of axolotl embryo s shows both cardiac and skeletal muscles to regulate the expression o f C-protein isoforms over a specific developmental window. Although th e CPRO(Axslow) isoform is present during the initial heartbeat stage, its expression is not retained in the adult heart. C-protein isoforms are simultaneously expressed in both cardiac and skeletal muscle durin g embryogenesis. (C) 1996 Wiley-Liss, Inc.