DEVELOPMENT OF CADHERIN-DEFINED PARASAGITTAL SUBDIVISIONS IN THE EMBRYONIC CHICKEN CEREBELLUM

The expression of three cadherins (cadherin-6B, cadherin-7, and R-cadh erin) was analyzed by immunohistochemistry at early to intermediate st ages of chicken cerebellar development (4.5-12 days of incubation [E4. 5-E12]). Expression was first detected at approximately E5. On the cer ebellar surface, expression of cadherin-6B and cadherin-7 is initially observed in transverse domains that subsequently elongate into parasa gittal stripes. The sequence of emergence, the borders, and the orient ation of these expression domains suggest a parcellation of the cerebe llum into distinct medial, lateral, and caudal embryonic subdivisions. These subdivisions relate to histologic features, to the expression o f gene regulatory proteins, and, possibly, to patterns of clonal restr iction. Individual cadherin-expressing cell clusters can be observed t o split into cortical and nuclear subdivisions, which are connected by nerve fibers expressing the same cadherin, thus establishing the para sagittal corticonuclear connectivity pattern found at later developmen tal stages. Our results suggest that cadherins may play a role in the transition from the early embryonic to the later functional organizati on of the cerebellum by providing a scaffold of potential adhesive cue s. J. Comp. Neurol. 401:367-381, 1998. (C) 1998 Wiley-Liss, Inc.