A reexamination of heart muscle differentiation in the postnodal piece of chick blastoderm mediated by exogenous RNA

Abstract

Previous findings on exogenous RNA-induced heart muscle differentiation in the non-heartforming cultured explants of the chick blastoderm, the postnodal pieces, were reexamined. Some of the changes that characterized the transition in the host tissues were: (i) the formation of highly ordered myofibrils; (ii) the appearance of characteristic cytoplasmic glycogen particles; (iii) a 2.5- and 3.5-fold increase in actin and myosin-like polypetides respectively; (iv) an increase in acetylcholinesterase activity; and (v) the acquisition of spontaneous and rhythmic pulsations. These specific changes appeared only in those explants that received a poly(A)-containing RNA fraction obtained from the 16-day-old chick embryonic heart. Neither synthetic polynucleotides nor a variety of RNA from several sources could replace the RNA from chick embryonic heart as an inducer of heart muscle differentiation.