The Journal of Neuroscience, April 2, 2008, 28(14):3707-3717; doi:10.1523/JNEUROSCI.4280-07.2008
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Development/Plasticity/Repair
Intermediate Progenitors in Adult Hippocampal Neurogenesis: Tbr2 Expression and Coordinate Regulation of Neuronal Output
Rebecca D. Hodge,1
Thomas D. Kowalczyk,1
Susanne A. Wolf,2
Juan M. Encinas,3
Caitlin Rippey,1
Grigori Enikolopov,3
Gerd Kempermann,2 and
Robert F. Hevner1
1Departments of Neurological Surgery and Pathology, University of Washington School of Medicine, Seattle, Washington 98101-1304, 2Max Delbrück Center for Molecular Medicine, 13125 Berlin, Germany, and 3Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724
Correspondence should be addressed to Robert F. Hevner, Seattle Children's Hospital Research Institute, Room 828, 1900 Ninth Avenue, Seattle, WA 98101-1304. Email: rhevner{at}u.washington.edu
Neurogenesis in the adult hippocampus is a highly regulated process that originates from multipotent progenitors in the subgranular zone (SGZ). Currently, little is known about molecular mechanisms that regulate proliferation and differentiation in the SGZ. To study the role of transcription factors (TFs), we focused on Tbr2 (T-box brain gene 2), which has been implicated previously in developmental glutamatergic neurogenesis. In adult mouse hippocampus, Tbr2 protein and Tbr2-GFP (green fluorescent protein) transgene expression were specifically localized to intermediate-stage progenitor cells (IPCs), a type of transit amplifying cells. The Tbr2+ IPCs were highly responsive to neurogenic stimuli, more than doubling after voluntary wheel running. Notably, the Tbr2+ IPCs formed cellular clusters, the average size of which (Tbr2+ cells per cluster) likewise more than doubled in runners. Conversely, Tbr2+ IPCs were selectively depleted by antimitotic drugs, known to suppress neurogenesis. After cessation of antimitotic treatment, recovery of neurogenesis was paralleled by recovery of Tbr2+ IPCs, including a transient rebound above baseline numbers. Finally, Tbr2 was examined in the context of additional TFs that, together, define a TF cascade in embryonic neocortical neurogenesis (Pax6
Ngn2
Tbr2
NeuroD
Tbr1). Remarkably, the same TF cascade was found to be linked to stages of neuronal lineage progression in adult SGZ. These results suggest that Tbr2+ IPCs play a major role in the regulation of adult hippocampal neurogenesis, and that a similar transcriptional program controls neurogenesis in adult SGZ as in embryonic cerebral cortex.
Key words: transcription factor; dentate gyrus; transit amplifying cells; glutamatergic neurons; subgranular zone; type-2 cells
Received Sept. 18, 2007;
revised Jan. 21, 2008;
accepted Feb. 23, 2008.
Correspondence should be addressed to Robert F. Hevner, Seattle Children's Hospital Research Institute, Room 828, 1900 Ninth Avenue, Seattle, WA 98101-1304. Email: rhevner{at}u.washington.edu
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S. J. Arnold, G.-J. Huang, A. F.P. Cheung, T. Era, S.-I. Nishikawa, E. K. Bikoff, Z. Molnar, E. J. Robertson, and M. Groszer
The T-box transcription factor Eomes/Tbr2 regulates neurogenesis in the cortical subventricular zone
Genes & Dev.,
September 15, 2008;
22(18):
2479 - 2484.
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