SELECTIVE ADHESION OF CELLS FROM DIFFERENT TELENCEPHALIC REGIONS

We asked whether specification of different regions of the rodent and avian telencephalon during development involved the acquisition of dif ferential adhesive properties. Cells from different regions were aggre gated in a short-term aggregation assay, and their segregation was ana lyzed. Both neurons and precursor cells from cortex segregate from str iatal cells at early, but not later, stages, whereas cells from rodent neocortex and hippocampus segregated only during later stages. Segreg ation was abolished when Ca2+-dependent but not Ca2+-independent adhes ion molecules were selectively removed. Thus, selective adhesion appea rs to be a conserved mechanism that restricts cellular mixing and migh t serve to maintain positional information during forebrain developmen t. A candidate for mediating the Ca2+-dependent segregation is the CD1 5 (Lewis(x)) carbohydrate epitope, which is selectively expressed by m ammalian cortex but not striatum.