KDM6 Demethylase Independent Loss of Histone H3 Lysine 27 Trimethylation during Early Embryonic Development

Abstract

The early mammalian embryo utilizes histone H3 lysine 27 trimethylation (H3K27me3) to maintain essential developmental genes in a repressive chromatin state. As differentiation progresses, H3K27me3 is removed in a distinct fashion to activate lineage specific patterns of developmental gene expression. These rapid changes in early embryonic chromatin environment are thought to be dependent on H3K27 demethylases. We have taken a mouse genetics approach to remove activity of both H3K27 demethylases of the Kdm6 gene family, Utx (Kdm6a, X-linked gene) and Jmjd3 (Kdm6b, autosomal gene). Male embryos null for active H3K27 demethylation by the Kdm6 gene family survive to term. At mid-gestation, embryos demonstrate proper patterning and activation of Hox genes. These male embryos retain the Y-chromosome UTX homolog, UTY, which cannot demethylate H3K27me3 due to mutations in catalytic site of the Jumonji-C domain. Embryonic stem (ES) cells lacking all enzymatic KDM6 demethylation exhibit a typical decrease in global H3K27me3 levels with differentiation. Retinoic acid differentiations of these ES cells demonstrate loss of H3K27me3 and gain of H3K4me3 to Hox promoters and other transcription factors, and induce expression similar to control cells. A small subset of genes exhibit decreased expression associated with reduction of promoter H3K4me3 and some low-level accumulation of H3K27me3. Finally, Utx and Jmjd3 mutant mouse embryonic fibroblasts (MEFs) demonstrate dramatic loss of H3K27me3 from promoters of several Hox genes and transcription factors. Our results indicate that early embryonic H3K27me3 repression can be alleviated in the absence of active demethylation by the Kdm6 gene family.

Parallel evolution of male germline epigenetic poising and somatic development in animals

“…These cell types are unique in that they can be 65 identified and reliably collected from whole testes in multiple mammalian species without the 66 use of transgenes or genetic markers (see Methods). In addition, they differ substantially from 67 each other in their place in the cell cycle and in the physical state of their chromatin: pachytenes 68 are tetraploid cells in meiotic prophase, with large nuclei and synapsed pairs of homologous 69 chromosomes, while round spermatids are haploid cells that have completed meiosis and have 70 small, compact nuclei. Inclusion of both cell types in our study allowed us to control for the 71 effects of chromatin compaction and physical state of the nucleus during spermatogenic 72 development.…”

Histone Demethylase KDM6A Controls the Mammary Luminal Lineage through Enzyme-Independent Mechanisms

“…In contrast, various lineage establishments require KDM6A protein but not its demethylase activity of KDM6A, including embryonic stem cell differentiation, Caenorhabditis elegans development, and early embryonic development (10,49,50). The role of KDM6A in regulating gene expression, aside from demethylating histones, is still not understood.…”

Inhibition of KDM6 activity during murine ESC differentiation induces DNA damage

“…However, part of the GSK-J4 effect has to involve H3K27 methylation as we see attenuation of treatment effects in differentiating Eed-KO ESCs. Recently, Shpargel et al have reported that KDM6A KDM6B double-KO embryos can develop to term and that repressed genes lose H3K27 methylation and are then expressed (Shpargel et al, 2014). The strategy used in the approach by Shpargel et al involved the deletion of KDM6B exons 14-21.…”