title: Transcription factors Mash-1 and Prox-1 delineate early steps in differentiation of neural stem cells in the developing central nervous system.
abstract: Like other tissues and organs in vertebrates, multipotential stem cells serve as the origin of diverse cell types during genesis of the mammalian central nervous system (CNS). During early development, stem cells self-renew and increase their total cell numbers without overt differentiation. At later stages, the cells withdraw from this self-renewal mode, and are fated to differentiate into neurons and glia in a spatially and temporally regulated manner. However, the molecular mechanisms underlying this important step in cell differentiation remain poorly understood. In this study, we present evidence that the expression and function of the neural-specific transcription factors Mash-1 and Prox-1 are involved in this process. In vivo, Mash-1- and Prox-1-expressing cells were defined as a transient proliferating population that was molecularly distinct from self-renewing stem cells. By taking advantage of in vitro culture systems, we showed that induction of Mash-1 and Prox-1 coincided with an initial step of differentiation of stem cells. Furthermore, forced expression of Mash-1 led to the down-regulation of nestin, a marker for undifferentiated neuroepithelial cells, and up-regulation of Prox-1, suggesting that Mash-1 positively regulates cell differentiation. In support of these observations in vitro, we found specific defects in cellular differentiation and loss of expression of Prox-1 in the developing brain of Mash-1 mutant mice in vivo. Thus, we propose that induction of Mash-1 and Prox-1 is one of the critical molecular events that control early development of the CNS.
authors.affiliation: Division of Neurobiology, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, Tokyo, 113-0033 Japan.
authors.forename: M a
authors.initials: Ma
authors.lastname: Torii
authors.forename: F
authors.initials: F
authors.lastname: Matsuzaki
authors.forename: N
authors.initials: N
authors.lastname: Osumi
authors.forename: K
authors.initials: K
authors.lastname: Kaibuchi
authors.forename: S
authors.initials: S
authors.lastname: Nakamura
authors.forename: S
authors.initials: S
authors.lastname: Casarosa
authors.forename: F
authors.initials: F
authors.lastname: Guillemot
authors.forename: M
authors.initials: M
authors.lastname: Nakafuku
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D015153:Blotting, Western; D002454:Cell Differentiation; D002478:Cells, Cultured; D002490:Central Nervous System / Q000166:cytology / Q000254:growth & development*; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D018257:Helix-Loop-Helix Motifs; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D017403:In Situ Hybridization; D051379:Mice; D018345:Mice, Knockout; D011817:Rabbits; D051381:Rats; D013234:Stem Cells / Q000166:cytology*; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D025521:Tumor Suppressor Proteins; D000098551:Prospero-Related Homeobox 1 Protein
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D000098551:Prospero-Related Homeobox 1 Protein; C499317:Ascl1 protein, mouse; C499318:Ascl1 protein, rat