Villin expression in the visceral endoderm and in the gut anlage during early mouse embryogenesis.

Villin is an evolutionarily well conserved, Ca2+ regulated actin-binding protein, and a major structural component of the brush border of specialized absorptive cells. Using paraffin sections and an affinity purified polyclonal anti-villin antibody, we have investigated the early expression of villin during mouse embryogenesis. Villin is first detectable at the early post-implantation stage in visceral endodermal cells at the periphery of the egg cylinder. In this extra embryonic layer, the expression of villin increases and then persists until full term gestation. In the embryo, villin first appears in gut anlage during the axial rotation. Using the same methodology, villin expression is also demonstrated in differentiating embryoid bodies from a teratocarcinoma. Both in extra embryonic and embryonic extracts, villin expression is confirmed by immunoblot and Northern blot analysis which reveal, respectively, a single polypeptide of 93 kd and an mRNA of 3.4 kb in length, two well defined parameters for adult mouse villin gene expression. The results presented here show that paraffin sections allow very sensitive and highly resolutive detection of antigens in early embryogenesis. They provide a detailed developmental profile of villin expression and demonstrate the usefulness of villin as a marker for epithelial cells involved in absorptive processes.