Developmental and regional regulation of rab3: a new brain specific "ras-like" gene

Recently, the expression of rab3, a new ras-like gene, has been shown to be restricted to brain tissues (Olofsson et al., 1988). This finding has prompted us to study the expression of rab3 in different brain regions of the developing mouse. The two transcripts corresponding to rab3 (1.8 and 1.3 kb) were first detected in the brains of E13 mouse embryos and were not randomly distributed. Highest levels were found in the mesencephalon, followed by the cortex, striatum, cerebellum, and brain stem in that order. In vitro, the expression of the 1.8-kb transcript was neuron specific, whereas the small transcript was present in neurons and astrocytes. This is the first report showing developmental and regional regulation of a nervous system-restricted ras-like gene. Based on the homologies found between the rab genes and YPT1 or sec-4, we suggest that the physiological role of rab3 might be related to the stabilization of the neuronal cytoskeleton or to post-Golgi vesicle transport and fusion.