Formation of cadherin-expressing brain nuclei in diencephalic alar plate divisions

During the formation of brain nuclei, the vertebrate neural tube is partiti oned into distinct embryonic divisions. In this study, the expression of th ree members of the cadherin family of adhesion molecules (cadherin-6B, cadh erin-7, and R-cadherin) was mapped to study the differentiation of gray mat ter in the divisions of the diencephalic alar plate of chicken embryos from embryonic day 3 (E3) to E10. At early stages of development (E3-E4), each cadherin is expressed in restricted regions of the diencephalic wall of the neural tube. The borders of some of the expression domains coincide with d ivisional boundaries. As the mantle layer is formed and increases in thickn ess from E4 to E8, morphologically discernible aggregates of cells appear t hat express the three cadherins differentially. These aggregates represent the anlagen of specific diencephalic brain nuclei, e.g., the lateroanterior nucleus, the ventral geniculate nucleus, the nucleus rotundus, the perirot undic area, the principal precommissural nucleus, and the lateral spiriform nucleus. Most of the cadherin-expressing diencephalic nuclei studied in th is work apparently derive from a single embryonic division and remain there . The divisional boundaries are replaced gradually by the borders of cadher in-expressing brain nuclei. The current results support the idea that cadhe rins confer differential adhesiveness to developing structures of gray matt er in the diencephalic alar plate. Moreover, they suggest that each cadheri n plays a role in the formation of specific brain nuclei within the diencep halic divisions. J. Comp. Neurol. 421:461-480, 2000. (C) 2000 Wiley-Liss, I nc.