Investigating Histone Demethylase Function During Hematopoietic Lineage Formation

Histone modifications serve as regulatory marks that help control gene expression and chromatin structure, and can facilitate transient and long term changes in gene transcription during organismal development. G9a/EHMT2 is a conserved histone methyltransferase that plays key roles during mammalian development through de novo dimethylation of histone H3 lysine 9 (H3K9me2), a mark associated with transcriptional silencing. We have recently discovered novel roles for G9a-H3K9me2 during lineage formation in human hematopoietic stem and progenitor cells (HSPCs): These include a role in specification of the megakaryopoietic/erythropoietic bi-potent progenitor (MEP) and an involvement in the reprogramming of epigenetic marks in the granulocyte, monocyte progenitor (GMP). In this application, we ask whether human Jumonji domain demethylases participate in these H3K9me2-dependent phenotypes and, more generally, whether they participate in HPSC lineage specification. To this end, we will first construct, assemble, and pre-validate RNAi reagents targeting 32 predicted Jumonji domain protein coding genes in the human genome. We then will use these reagents in isolated human HSPCs to determine whether Jumonji domain genes modulate lineage fate choice or MEP/GMP-specific H3K9me2 patterning during lineage specification.
We will specifically test the hypotheses that one or more Jumonji domain genes, a) promotes self-renewal of HSCs through counteracting G9a-H3K9me2 and b) promotes global loss of G9a-H3K9me2 during GMP formation. If successful, these results will uncover novel roles for histone demethylases during HSPC lineage formation and identify additional molecular manipulations with which to control stem cell fate, e.g. true self replication, and directed lineage commitment. In addition, the RNAi-Jumonji gene library will be a valuable resource to Progenitor Cell Biology Consortium members interested in examining histone methylation in a wide variety of stem cell types and systems.

Copyright ©2013 NHLBI Progenitor Cell Biology Consortium.

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