THE PROTHYMOSIN-ALPHA GENE IS SPECIFICALLY EXPRESSED IN ECTODERMAL AND MESODERMAL REGIONS DURING EARLY POSTIMPLANTATION MOUSE EMBRYOGENESIS

Prothymosin alpha (ProT alpha) is a highly acidic nuclear protein, onc e believed to have an extracellular immunoregulatory role but more rec ently implicated in cell proliferation and/or differentiation. Several recent studies have revealed that ProT alpha mRNA is present during e mbryogenesis. However, these studies did not investigate the spatial d istribution of ProT alpha mRNA in the embryo. Here we present a detail ed study of the spatial distribution of ProT alpha mRNA during the ear ly stages of postimplantation development (6.5-12.5 dpc) of the mouse. Three findings are of particular interest. First, ProT alpha mRNA lev els increase during the early postimplantation stages (6.5-8.5 dpc) of mouse embryogenesis. Second, ProT alpha mRNA is not uniformly distrib uted in the mouse embryo, but is present in a spatially specific manne r. Third, we have observed that the mouse ProT alpha gene is expressed almost exclusively in ectodermal and mesoderm-derived structures, and not in cells which give rise to the definitive endoderm.