Expression of N-cadherin mRNA during development of the mouse brain.

The expression of N-cadherin mRNA was mapped in the brain of mice between embryonic day 12 (E12) and the adult stage by in situ hybridization of digoxigenin-labeled riboprobe. Two phases of N-cadherin expression can be distinguished. During the first phase (about E12 to E16), expression is ubiquitous throughout the brain and most prominent in the proliferative neuroepithelium. During the second phase (about E16 to postnatal day 6), N-cadherin expression is restricted to particular nuclei or laminae that share common functional features and neuroanatomical connections. Several of the N-cadherin-positive structures receive direct afferents from retinal ganglion cells or from the superior colliculus. Others belong to the reticular system and to the limbic system of the brain. In neocortex, N-cadherin is expressed by deeper layer cells. In the adult brain, only low levels of N-cadherin expression remain in very few types of cells, for example in the Purkinje cells of the cerebellum. These results are similar to data from chicken brain and suggest that the generalized expression of N-cadherin during the early phase and the restriction expression of this molecule in particular functional systems during the later phase is, at least in part, phylogenetically conserved between chicken and mouse. Moreover, the results show that N-cadherin expression extends to phylogenetically newer structures, e.g., the mammalian neocortex.