Neurogenesis in adult dentate gyrus: Evidence of mitosis in differentiated granule cells following spatial learning

An increasing body of evidence has been presented to demonstrate the idea that neurogenesis occurs only during development and ends before puberty is erroneous. In adult vertebrate brain, neurogenesis persists throughout life mainly in two discrete regions – the dentate gyrus of the hippocampus (DG) and the olfactory bulb. Neurogenesis has been shown by detection of tagged thymidine analogues which are incorporated into the S phase of the cell cycle, but these
may also detect repaired DNA in post-mitotic neurons and/or an abortive cell cycle. Recent retroviral labelling has shown that neuronal progenitors/neuroblasts divide and produce functional neurons. However, it is unclear whether differentiated granule cells (GC) in the DG can divide and give rise to another GC. We have used three-dimensional (3D) reconstructions of serial ultrathin sections to identify and reconstruct GC, thereby illustrating individual mitotic elements and phases. We report that functional GC with clear synaptic specializations re-enter the cell cycle demonstrating for the first time that newly generated neurons within the DG can arise not only from stem cell precursors, but also from differentiated GC.

Neurogenesis in adult dentate gyrus: Evidence of mitosis in differentiated granule cells following spatial learning
V.Popov, J.J.Rodriguez, H.A.Davies, I.V.Kraev, D.Banks, M.I.Cordero, C.Sandi and M.G.Stewart
18TH NATIONAL MEETING OF THE BRITISH NEUROSCIENCE ASSOCIATION 2005