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Astrocyte-specific genes are generally demethylated in neural precursor cells prior to astrocytic differentiation.

Hatada I, Namihira M, Morita S, Kimura M, Horii T, Nakashima K - PLoS ONE (2008)

Bottom Line: This differentiation-potential switch could be explained by epigenetic changes, since the promoters of astrocyte-specific marker genes, glial fibrillary acidic protein (Gfap) and S100beta, have been shown to become demethylated in late-stage NPCs prior to the onset of astrocyte differentiation; however, whether demethylation occurs generally in other astrocyctic genes remains unknown.Although these genes are already demethylated in late-stage NPCs, they are not expressed until cells differentiate into astrocytes.Thus, late-stage NPCs have epigenetic potential which can be realized in their expression after astrocyte differentiation.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Genome Science, Biosignal Genome Resource Center, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan. ihatada@showa.gunma-u.ac.jp

ABSTRACT
Epigenetic changes are thought to lead to alterations in the property of cells, such as differentiation potential. Neural precursor cells (NPCs) differentiate only into neurons in the midgestational brain, yet they become able to generate astrocytes in the late stage of development. This differentiation-potential switch could be explained by epigenetic changes, since the promoters of astrocyte-specific marker genes, glial fibrillary acidic protein (Gfap) and S100beta, have been shown to become demethylated in late-stage NPCs prior to the onset of astrocyte differentiation; however, whether demethylation occurs generally in other astrocyctic genes remains unknown. Here we analyzed DNA methylation changes in mouse NPCs between the mid-(E11.5) and late (E14.5) stage of development by a genome-wide DNA methylation profiling method using microarrays and found that many astrocytic genes are demethylated in late-stage NPCs, enabling the cell to become competent to express these genes. Although these genes are already demethylated in late-stage NPCs, they are not expressed until cells differentiate into astrocytes. Thus, late-stage NPCs have epigenetic potential which can be realized in their expression after astrocyte differentiation.

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Screening of conserved STAT and SMAD binding sites in demethylated and upregulated genes.Schematic representation of screening of conserved STAT and SMAD binding sites in hypomethylated genes both in E14.5 NPCs and astrocytes. Numbers of genes are indicated in parentheses.
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pone-0003189-g008: Screening of conserved STAT and SMAD binding sites in demethylated and upregulated genes.Schematic representation of screening of conserved STAT and SMAD binding sites in hypomethylated genes both in E14.5 NPCs and astrocytes. Numbers of genes are indicated in parentheses.

Mentions: A CpG sequence in a conserved STAT-binding site in the Gfap gene promoter is methylated in NPCs midgestation when astrogliogenesis does not normally commence; however, it becomes demethylated in late gestational NPCs that have gained the potential to differentiate into astrocytes [15]. Thus, the Gfap gene with the hypomethylated promoter can be expressed upon astrocyte differentiation induced by LIF, which activates the JAK/STAT signaling pathway [13]. Therefore, we searched for conserved STAT-binding sites in the genes hypomethylated both in E14.5 NPCs and astrocytes compared to E11.5 NPCs. To avoid omitting threshold level genes, the threshold used in E14.5 NPCs was extended (D10<0.5). Among these genes, those that showed upregulation in E14.5 NPCs or astrocytes compared to E11.5 NPCs were used for analysis (Fig. 8). Sequences including 500-(basepair) bp upstream and 500-bp downstream of the probes were searched for STAT3 binding sites with the CpG sequence (TTN4-6AA, CG in any N position). Such methylation-sensitive STAT binding sites were found among these 18 genes; however, none were conserved between mice and humans except for Gfap, which shows hypomethylation both in E14.5 NPCs and astrocytes (Fig. 1). Although we cannot rule out the possibility that some demethylated STAT binding sites were not detected by the MIAMI method because of its target limitation, these results suggest that not all astrocyte-specific genes are epigenetically controlled only via STAT binding site methylation.


Astrocyte-specific genes are generally demethylated in neural precursor cells prior to astrocytic differentiation.

Hatada I, Namihira M, Morita S, Kimura M, Horii T, Nakashima K - PLoS ONE (2008)

Screening of conserved STAT and SMAD binding sites in demethylated and upregulated genes.Schematic representation of screening of conserved STAT and SMAD binding sites in hypomethylated genes both in E14.5 NPCs and astrocytes. Numbers of genes are indicated in parentheses.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2527128&req=5

pone-0003189-g008: Screening of conserved STAT and SMAD binding sites in demethylated and upregulated genes.Schematic representation of screening of conserved STAT and SMAD binding sites in hypomethylated genes both in E14.5 NPCs and astrocytes. Numbers of genes are indicated in parentheses.
Mentions: A CpG sequence in a conserved STAT-binding site in the Gfap gene promoter is methylated in NPCs midgestation when astrogliogenesis does not normally commence; however, it becomes demethylated in late gestational NPCs that have gained the potential to differentiate into astrocytes [15]. Thus, the Gfap gene with the hypomethylated promoter can be expressed upon astrocyte differentiation induced by LIF, which activates the JAK/STAT signaling pathway [13]. Therefore, we searched for conserved STAT-binding sites in the genes hypomethylated both in E14.5 NPCs and astrocytes compared to E11.5 NPCs. To avoid omitting threshold level genes, the threshold used in E14.5 NPCs was extended (D10<0.5). Among these genes, those that showed upregulation in E14.5 NPCs or astrocytes compared to E11.5 NPCs were used for analysis (Fig. 8). Sequences including 500-(basepair) bp upstream and 500-bp downstream of the probes were searched for STAT3 binding sites with the CpG sequence (TTN4-6AA, CG in any N position). Such methylation-sensitive STAT binding sites were found among these 18 genes; however, none were conserved between mice and humans except for Gfap, which shows hypomethylation both in E14.5 NPCs and astrocytes (Fig. 1). Although we cannot rule out the possibility that some demethylated STAT binding sites were not detected by the MIAMI method because of its target limitation, these results suggest that not all astrocyte-specific genes are epigenetically controlled only via STAT binding site methylation.

Bottom Line: This differentiation-potential switch could be explained by epigenetic changes, since the promoters of astrocyte-specific marker genes, glial fibrillary acidic protein (Gfap) and S100beta, have been shown to become demethylated in late-stage NPCs prior to the onset of astrocyte differentiation; however, whether demethylation occurs generally in other astrocyctic genes remains unknown.Although these genes are already demethylated in late-stage NPCs, they are not expressed until cells differentiate into astrocytes.Thus, late-stage NPCs have epigenetic potential which can be realized in their expression after astrocyte differentiation.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Genome Science, Biosignal Genome Resource Center, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan. ihatada@showa.gunma-u.ac.jp

ABSTRACT
Epigenetic changes are thought to lead to alterations in the property of cells, such as differentiation potential. Neural precursor cells (NPCs) differentiate only into neurons in the midgestational brain, yet they become able to generate astrocytes in the late stage of development. This differentiation-potential switch could be explained by epigenetic changes, since the promoters of astrocyte-specific marker genes, glial fibrillary acidic protein (Gfap) and S100beta, have been shown to become demethylated in late-stage NPCs prior to the onset of astrocyte differentiation; however, whether demethylation occurs generally in other astrocyctic genes remains unknown. Here we analyzed DNA methylation changes in mouse NPCs between the mid-(E11.5) and late (E14.5) stage of development by a genome-wide DNA methylation profiling method using microarrays and found that many astrocytic genes are demethylated in late-stage NPCs, enabling the cell to become competent to express these genes. Although these genes are already demethylated in late-stage NPCs, they are not expressed until cells differentiate into astrocytes. Thus, late-stage NPCs have epigenetic potential which can be realized in their expression after astrocyte differentiation.

Show MeSH