RNA synthesis in te early embryogenesis of a fish (Misgurnus fossilis).

Synthesis of ribonucleic acids in early embryos has been extensively studied during recent years in a number of laboratories and has been shown to begin shortly after fertilization (Kafiani, Tatarskaya & Kanopkayte, 1958; Wilt, 1963; Brown & Littna, 1964; Decroly, Cape & Brachet, 1964; Glisin & Glisin, 1964; Kafiani & Timofeeva, 1964, 1965; Nemer & Infant, 1965). Early embryos of Xenopus (Brown & Gurdon, 1964; Brown & Littna, 1964, 1966) and of sea urchins (Wilt, 1963; Glisin & Glisin, 1964; Nemer & Infant, 1965) synthesize up to gastrula stage predominantly or exclusively polydisperse RNA of a nonribosomal nature usually referred to as DNA-like RNA (dRNA). The occurrence of continuous dRNA synthesis in early embryogenesis is in apparent conflict with the periodicity of the 'morphogenetic function' of cell nuclei found by one of us (Neyfakh, 1959, 1961, 1964, 1965) in embryos of a number of animal species. In fact, for a certain time after ferilization of eggs with a regulatory type of development, the nuclei remain morphogenetically inactive. Microsurgical (Harvey, 1940; Briggs & King, 1959), chemical (Gross & Cousineau, 1963; Lallier, 1963; Gross, Malkin & Moyer, 1964; Neyfakh, 1965) or radiation-induced (Neyfakh, 1959, 1961; Neyfakh & Rott, 1958; Shapiro & Lander, 1960) enucleation of the egg does not visibly affect early development up to the late blastula stage. After the initial period of inactivity, a period of 'morphogenetic activity' of the nuclei begins which assures the process of gastrulation. The occurrence of dRNA synthesis starting immediately or shortly after fertilization is hard to reconcile with the proposal of a direct relationship between the morphogenetic and the biochemical (dRNA-synthesizing) functions of cell nuclei. This work seeks to analyse this apparent contraction, to further understanding of the molecular basis of early embryogenesis.