Expression of Patella vulgata Orthologs of engrailed and dpp-BMP2/4 in Adjacent Domains during Molluscan Shell Development Suggests a Conserved Compartment Boundary Mechanism

The engrailed gene is well known from its role in segmentation and central nervous system development in a variety of species. In molluscs, however, engrailed is involved in shell formation. So far, it seemed that engrailed had been co-opted uniquely for this particular process in molluscs. Here, we show that, in the gastropod mollusc Patella vulgata, an engrailed ortholog is expressed in the edge of the embryonic shell and in the anlage of the...