Amphibian intestinal villin: isolation and expression during embryonic and larval development.

An actin-binding protein of M(r) 105,000 has been isolated from anuran amphibian intestinal mucosa. Polyclonal antibodies directed against chicken and pig intestinal villins and anti-porcine villin headpiece monoclonal antibody crossreact with the amphibian M(r) 105,000 protein. Furthermore, the latter possesses an NH2-terminal sequence that is very homologous to those of avian and mammalian villins. In addition, polyclonal antibodies directed against amphibian intestinal M(r) 105,000 protein crossreact with chicken and mouse intestinal epithelial cell villins. These data indicate that the amphibian intestinal M(r) 105,000 protein is immunologically and structurally related to villin, an actin-binding protein expressed in specific epithelial tissues in vertebrates. Morphological, immunocytochemical and immunoblotting techniques were then used to investigate the expression of villin during embryonic and larval intestinal development of Xenopus laevis. Villin is not found in the egg or the endoderm of the early embryo. It is first detected just before hatching in the apical domain of endodermal cells at a time when few surface microvilli are visible by transmission electron microscopy. In the newly hatched larva, villin accumulates as these cells differentiate. These results provide a detailed developmental profile of Xenopus intestinal villin expression and demonstrate that this protein is a useful marker for the presumptive intestinal endoderm.