Chromatin-based mechanisms are pivotal regulators of transcriptional patterns that are central to cell fate determination, organogenesis and development in multicellular organisms. The activity of Polycomb Repressive Complex 2 (PRC2) is involved in the maintenance of transcriptional gene repression by catalyzing the trimethylation of histone H3 on lysine 27 at specific loci, and is a conserved modulator of developmental programs.
To reveal the extent to which PRC2 shapes transcriptional decisions during cell fate specification, I have characterized the epigenome organization of a single cell type from the root stem cell niche (SCN). Quantitative integration of (epi)-genomic data revealed three main chromatin states that correlate with distinct gene expression levels as well as patterns along the differentiation gradient. These results indicate that PRC2 activity over specific genes within the SCN regulates their timing of expression in daughter cells, at successive differentiation stages.
In addition, functional studies of PRC2 catalytic subunit homologues support the notion that distinct PRC2 complexes with different compositions cooperate to fine-tune the transcriptional regulation of key regulatory genes during root development.
Taken together, this work highlights the importance of PRC2-regulated chromatin states in shaping expression patterns along a differentiation gradient. They also pinpoint the potential of such epigenetic studies in predicting, from an initial chromatin state, the timing of gene transcriptional activation in subsequent differentiation stages.
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