title: Smad4 and Trim33/Tif1γ redundantly regulate neural stem cells in the developing cortex.
abstract: During central nervous system (CNS) development, proliferation and differentiation of neural stem cells (NSCs) have to be regulated in a spatio-temporal fashion. Here, we report different branches of the transforming growth factor β (TGFβ) signaling pathway to be required for the brain area-specific control of NSCs. In the midbrain, canonical TGFβ signaling via Smad4 regulates the balance between proliferation and differentiation of NSCs. Accordingly, Smad4 deletion resulted in horizontal expansion of NSCs due to increased proliferation, decreased differentiation, and decreased cell cycle exit. In the developing cortex, however, ablation of Smad4 alone did not have any effect on proliferation and differentiation of NSCs. In contrast, concomitant mutation of both Smad4 and Trim33 led to an increase in proliferative cells in the ventricular zone due to decreased cell cycle exit, revealing a functional redundancy of Smad4 and Trim33. Furthermore, in Smad4-Trim33 double mutant embryos, cortical NSCs generated an excess of deep layer neurons concurrent with a delayed and reduced production of upper layer neurons and, in addition, failed to undergo the neurogenic to gliogenic switch at the right developmental stage. Thus, our data disclose that in different regions of the developing CNS different aspects of the TGFβ signaling pathway are required to ensure proper development.
authors.affiliation: Division of Cell and Developmental Biology, Institute of Anatomy, University of Zurich, Zurich, Switzerland, Current address: Helmholtz Center Munich, German Research Center for Environmental Health, Institute for Stem Cell Research, D-85764 Neuherberg, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Falk
authors.affiliation: Division of Cell and Developmental Biology, Institute of Anatomy, University of Zurich, Zurich, Switzerland.
authors.forename: Esméé
authors.initials: E
authors.lastname: Joosten
authors.affiliation: Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI 48109, USA and.
authors.forename: Vesa
authors.initials: V
authors.lastname: Kaartinen
authors.affiliation: Division of Cell and Developmental Biology, Institute of Anatomy, University of Zurich, Zurich, Switzerland.
authors.forename: Lukas
authors.initials: L
authors.lastname: Sommer
mesh_terms: D000367:Age Factors; D000818:Animals; D002453:Cell Cycle / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D049109:Cell Proliferation / Q000502:physiology; D002540:Cerebral Cortex / Q000166:cytology* / Q000196:embryology; D004622:Embryo, Mammalian; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D008636:Mesencephalon / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation / Q000235:genetics; D058953:Neural Stem Cells / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D011247:Pregnancy; D055748:SOXB1 Transcription Factors / Q000378:metabolism; D051901:Smad4 Protein / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D051155:Wnt1 Protein / Q000235:genetics / Q000378:metabolism; D000099260:Empty Spiracles Homeobox Proteins
chemical_list: D018398:Homeodomain Proteins; D055748:SOXB1 Transcription Factors; D051901:Smad4 Protein; D014157:Transcription Factors; D051155:Wnt1 Protein; D000099260:Empty Spiracles Homeobox Proteins; C490810:Smad4 protein, mouse; C527783:Sox2 protein, mouse; C491420:Trim33 protein, mouse; C495246:Wnt1 protein, mouse
keywords: Smad4; Trim33; brain development; cortex; neural stem cells