REGIONAL DISTRIBUTION OF MATERNAL MESSENGER-RNA SOX-19 IN THE ZEBRAFISH EARLY EMBRYO

Asymmetric distribution of mRNA has been associated with polarisation and cell fate determination during early development of animal embryos . In this report we determine the distribution pattern of Zf-Sox 19 mR NA during early embryogenesis of zebrafish. Zf-Sox 19 mRNA is found in one pole of the embryo at the 8-cell stage and in the deep cell layer close to the yolk, perhaps under the influence of yolk determinants. Zf-Sox 19 is the earliest gene in zebrafish development whose RNA show s a restricted localisation. This result indicates that the first eigh t blastomeres are not equivalent in their molecular components.