title: Basal progenitor cells in the embryonic mouse thalamus - their molecular characterization and the role of neurogenins and Pax6.
abstract: BACKGROUND
  The size and cell number of each brain region are influenced by the organization and behavior of neural progenitor cells during embryonic development. Recent studies on developing neocortex have revealed the presence of neural progenitor cells that divide away from the ventricular surface and undergo symmetric divisions to generate either two neurons or two progenitor cells. These 'basal' progenitor cells form the subventricular zone and are responsible for generating the majority of neocortical neurons. However, not much has been studied on similar types of progenitor cells in other brain regions.
  
  
  RESULTS
  We have identified and characterized basal progenitor cells in the embryonic mouse thalamus. The progenitor domain that generates all of the cortex-projecting thalamic nuclei contained a remarkably high proportion of basally dividing cells. Fewer basal progenitor cells were found in other progenitor domains that generate non-cortex projecting nuclei. By using intracellular domain of Notch1 (NICD) as a marker for radial glial cells, we found that basally dividing cells extended outside the lateral limit of radial glial cells, indicating that, similar to the neocortex and ventral telencephalon, the thalamus has a distinct subventricular zone. Neocortical and thalamic basal progenitor cells shared expression of some molecular markers, including Insm1, Neurog1, Neurog2 and NeuroD1. Additionally, basal progenitor cells in each region also expressed exclusive markers, such as Tbr2 in the neocortex and Olig2 and Olig3 in the thalamus. In Neurog1/Neurog2 double mutant mice, the number of basally dividing progenitor cells in the thalamus was significantly reduced, which demonstrates the roles of neurogenins in the generation and/or maintenance of basal progenitor cells. In Pax6 mutant mice, the part of the thalamus that showed reduced Neurog1/2 expression also had reduced basal mitosis.
  
  
  CONCLUSIONS
  Our current study establishes the existence of a unique and significant population of basal progenitor cells in the thalamus and their dependence on neurogenins and Pax6. These progenitor cells may have important roles in enhancing the generation of neurons within the thalamus and may also be critical for generating neuronal diversity in this complex brain region.
authors.affiliation: Department of Neuroscience, Developmental Biology Center and Stem Cell Institute, University of Minnesota, Minneapolis, MN 55455, USA. nakagawa@umn.edu
authors.forename: Lynn
authors.initials: L
authors.lastname: Wang
authors.forename: Krista K
authors.initials: KK
authors.lastname: Bluske
authors.forename: Lauren K
authors.initials: LK
authors.lastname: Dickel
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Nakagawa
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D005136:Eye Proteins / Q000235:genetics / Q000502:physiology*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D019579:Neocortex / Q000166:cytology / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism; D058953:Neural Stem Cells / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors / Q000235:genetics / Q000502:physiology*; D011247:Pregnancy; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D013788:Thalamus / Q000166:cytology* / Q000196:embryology / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D005136:Eye Proteins; D018398:Homeodomain Proteins; D009419:Nerve Tissue Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; D014157:Transcription Factors; C501008:Neurod1 protein, mouse; C102938:Neurog2 protein, mouse; C000605732:Pax6 protein, mouse; C486336:Neurog1 protein, mouse
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