Identification And Characterization Of Neuroblasts And The Progenitor Domains In The Adult And Fetal Human Brain

Adult mammals brains contains neural stem cells, which can generated new neurons. It is of great interest to identify new neurons in the adult human brain, but the persistence of neurogenesis in the subventricular zone (SVZ) and the existence of the rostral migratory stream (RMS)-like pathway in the adult human forebrain remain highly controversial. In the present study, we have described the general configuration of the RMS in adult monkey, fetal human and adult human brains. We provide evidence that neuroblasts exist continuously in the anterior ventral SVZ and RMS of the adult human brain. The neuroblasts appear singly or in pairs without forming chains; they exhibit migratory morphologies and co-express the immature neuronal markers doublecortin, polysialylated neural cell adhesion molecule and βⅢ-tubulin. Few of these neuroblasts appear to be actively proliferating in the anterior ventral SVZ but none in the RMS, indicating that neuroblasts distributed along the RMS are most likely derived from the ventral SVZ. Interestingly, no neuroblasts are found in the adult human olfactory bulb. Taken together, our data suggest that the SVZ maintains the ability to produce neuroblasts in the adult human brain. The human telencephalon, comprising a large number of distinct types of neurons, is considered the most complex biological structure known to science. However, our understanding of the origin of neural diversity in the mammalian telencephalon has been largely obtained from mice. Using several transcription factors, such as Pax6, Nkx2.1, Sp8and COUP-TFII, we have revealed that the expression patterns of in the developing human telencephalon are similar to that of the murine brain, which enables us to successfully identify four main proliferative domains:the dorsal telencephalon ventricular/subventricular zone and the lateral, medial, and caudal ganglionic eminences. This study generates a molecular map of the different progenitor domains present in the developing human telencephalon and should serve as a basis for a better understanding of the generation of neuronal diversity in the human forebrain.