Identification of genes that restrict astrocyte differentiation of midgestational neural precursor cells.
During development of the mammalian CNS, neurons and glial cells (astrocytes and oligodendrocytes) are generated from common neural precursor cells (NPCs). However, neurogenesis precedes gliogenesis, which normally commences at later stages of fetal telencephalic development. Astrocyte differentiation of mouse NPCs at embryonic day (E) 14.5 (relatively late gestation) is induced by activation of the transcription factor signal transducer and activator of transcription (STAT) 3, whereas at E11.5 (mid-gestation) NPCs do not differentiate into astrocytes even when stimulated by STAT3-activating cytokines such as leukemia inhibitory factor (LIF). This can be explained in part by the fact that astrocyte-specific gene promoters are highly methylated in NPCs at E11.5, but other mechanisms are also likely to play a role. We therefore sought to identify genes involved in the inhibition of astrocyte differentiation of NPCs at midgestation. We first examined gene expression profiles in E11.5 and E14.5 NPCs, using Affymetrix GeneChip analysis, applying the Percellome method to normalize gene expression level. We then conducted in situ hybridization analysis for selected genes found to be highly expressed in NPCs at midgestation. Among these genes, we found that N-myc and high mobility group AT-hook 2 (Hmga2) were highly expressed in the E11.5 but not the E14.5 ventricular zone of mouse brain, where NPCs reside. Transduction of N-myc and Hmga2 by retroviruses into E14.5 NPCs, which normally differentiate into astrocytes in response to LIF, resulted in suppression of astrocyte differentiation. However, sustained expression of N-myc and Hmga2 in E11.5 NPCs failed to maintain the hypermethylated status of an astrocyte-specific gene promoter. Taken together, our data suggest that astrocyte differentiation of NPCs is regulated not only by DNA methylation but also by genes whose expression is controlled spatio-temporally during brain development.
Sanosaka
T
T
Laboratory of Molecular Neuroscience, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5, Takayama, Ikoma, Nara 630-0101, Japan.
Namihira
M
M
Asano
H
H
Kohyama
J
J
Aisaki
K
K
Igarashi
K
K
Kanno
J
J
Nakashima
K
K
D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics*; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D025743:HMGA2 Protein / Q000235:genetics / Q000378:metabolism; D053605:Leukemia Inhibitory Factor / Q000494:pharmacology; D051379:Mice; D008813:Mice, Inbred ICR; D009474:Neurons / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D011247:Pregnancy; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism; D013234:Stem Cells / Q000502:physiology*; D014158:Transcription, Genetic / Q000502:physiology*; D014161:Transduction, Genetic / Q000379:methods
D025743:HMGA2 Protein; D053605:Leukemia Inhibitory Factor; D016271:Proto-Oncogene Proteins c-myc; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D049452:Green Fluorescent Proteins