DEVELOPMENTAL EXPRESSION OF PC3 GENE IS CORRELATED WITH NEURONAL CELLBIRTHDAY

We examined the developmental expression of PC3, a nerve growth factor (NGF) early induced gene in PC12 cells, in the rat central nervous sy stem (CNS) and we found that it represents a molecular marker of ongoi ng postmitotic neurons production. PC3 is initially expressed in the v entral quarter of the neural tube, at the level of the presumptive cer vical spinal cord just where and when (10-11 days post coitum (dpc)) t he motor neurons are arising. Subsequently, the appearance of PC3 expr ession follows a ventro-dorsal and a rostro-caudal gradient in the spi nal cord and a caudo-rostral gradient across the brain vesicles that c oincide, both spatially and temporally, with the gradients of neurogen esis described in the literature. As in PC12 cells, PC3 mRNA expressio n appears to be transient in vivo. In all regions of the CNS, it is re stricted to the ventricular zone of the neuroepithelium, while neurona l precursors cease to express PC3 as they migrate to the mantle zone. Moreover, PC3 mRNA disappears from the various regions of the CNS as n eurogenesis ceases.