Latexin: a molecular marker for regional specification in the neocortex.

It largely remains to be elucidated how the mammalian neocortex is regionally specified during development. In an attempt to obtain molecular markers in the neocortex, we have generated a monoclonal antibody PC3.1 which recognizes a subset of neurons located in lateral, but not dorsal, neocortical areas. The antigen is a novel class of protein, named latexin, having a molecular weight of 29,000. Our in vitro studies have revealed that the neocortical regional specification for the production of latexin-positive neurons occurs very early prior to thalamocortical interactions and the completion of neurogenesis, indicating that elements intrinsic to the neocortex play important roles in the neocortical specification. Furthermore, our recent analyses have suggested that this regional specification is attributable, at least in part, to an early restriction of developmental potential in neocortical progenitor cells to become latexin-positive neurons.