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Genomic Prevalence of Heterochromatic H3K9me2 and Transcription Do
Not Discriminate Pluripotent from Terminally Differentiated
Cells


Cellular differentiation entails reprogramming of the transcriptome from a

pluripotent to a unipotent fate. This process was suggested to coincide with a

global increase of repressive heterochromatin, which results in a reduction of

transcriptional plasticity and potential. Here we report the dynamics of the

transcriptome and an abundant heterochromatic histone modification,

dimethylation of histone H3 at lysine 9 (H3K9me2), during neuronal

differentiation of embryonic stem cells. In contrast to the prevailing model, we

find H3K9me2 to occupy over 50% of chromosomal regions already in stem

cells. Marked are most genomic regions that are devoid of transcription and a

subgroup of histone modifications. Importantly, no global increase occurs during

differentiation, but discrete local changes of H3K9me2 particularly at genic

regions can be detected. Mirroring the cell fate change, many genes show altered

expression upon differentiation. Quantitative sequencing of transcripts

demonstrates however that the total number of active genes is equal between stem

cells and several tested differentiated cell types. Together, these findings

reveal high prevalence of a heterochromatic mark in stem cells and challenge the

model of low abundance of epigenetic repression and resulting global basal level

transcription in stem cells. This suggests that cellular differentiation entails

local rather than global changes in epigenetic repression and transcriptional

activity.


Vyšlo v časopise: Genomic Prevalence of Heterochromatic H3K9me2 and Transcription Do Not Discriminate Pluripotent from Terminally Differentiated Cells. PLoS Genet 7(6): e32767. doi:10.1371/journal.pgen.1002090
Kategorie: Research Article
prolekare.web.journal.doi_sk: https://doi.org/10.1371/journal.pgen.1002090

Souhrn

Cellular differentiation entails reprogramming of the transcriptome from a

pluripotent to a unipotent fate. This process was suggested to coincide with a

global increase of repressive heterochromatin, which results in a reduction of

transcriptional plasticity and potential. Here we report the dynamics of the

transcriptome and an abundant heterochromatic histone modification,

dimethylation of histone H3 at lysine 9 (H3K9me2), during neuronal

differentiation of embryonic stem cells. In contrast to the prevailing model, we

find H3K9me2 to occupy over 50% of chromosomal regions already in stem

cells. Marked are most genomic regions that are devoid of transcription and a

subgroup of histone modifications. Importantly, no global increase occurs during

differentiation, but discrete local changes of H3K9me2 particularly at genic

regions can be detected. Mirroring the cell fate change, many genes show altered

expression upon differentiation. Quantitative sequencing of transcripts

demonstrates however that the total number of active genes is equal between stem

cells and several tested differentiated cell types. Together, these findings

reveal high prevalence of a heterochromatic mark in stem cells and challenge the

model of low abundance of epigenetic repression and resulting global basal level

transcription in stem cells. This suggests that cellular differentiation entails

local rather than global changes in epigenetic repression and transcriptional

activity.


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Štítky
Genetika Reprodukčná medicína

Článok vyšiel v časopise

PLOS Genetics


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