Cell migration domains in the chick telencephalon

[摘要] Little is known about the process by which the vertebrate forebrain (the diencephalon and telencephalon) becomes regionalized during development. In studies reported here, DiI injections were used to label the embryonic day 3 (stage-16) chick telencephalon in ovo , and the migration patterns of labelled cells were analyzed in relation to various molecular markers, including the regulatory genes Cash-l and Sonic hedgehog (Shh). Cells generated in the ventral telencephalon (basal ventricular ridge, or BVR) were found to migrate widely, but were restricted from crossing into the more dorsal telencephalon (dorsal ventricular ridge, or DVR), and the more caudaldiencephalon. The cell migration boundary between the BVR and DVR correlates with a Cash-l expression boundary, and the cell migration boundary between BVR and diencephalon correlates with a Shh expression boundary. In addition, cellmigration patterns were dramatically different in the BVR and DVR territories. These results suggest that the BVR represents a "cell migration domain," or a true unit oftelencephalic compartmental organization, which is distinct from cell migration domains in both the DVR and diencephalon. In addition, two lines of evidence in theearly embryo are shown to support the proposal that avian BVR is homologous to mammalian basal ganglia, and that avian DVR is homologous to mammalian cerebral cortex: regulatory gene expression patterns in the chick and mouse telencephalon are very similar; and the cell migration patterns in the chick telencephalon demonstrated here are found to correspond closely to those previously reported in the mouse telencephalon.Using the same DiI labelling technique, a regional fate map of the stage-16 chick telencephalon was derived. This fate map can now be used to guide transplantation or misexpression experiments, and to interpret gene expressionpatterns in the stage-16 telencephalon. For example, though Cash-l is expressed in the entire BVR at ES-E7 (stage 24-30), superimposition of its expression pattern onto the stage-16 fate map shows that it is only expressed in a subregion of the presumptive BVR at stage-16.

[发布机构] University:California Institute of Technology;Department:Biology

[关键词] Cellular and Molecular Neurobiology