DOT1L-Mediated H3K79 Methylation in Chromatin Is Dispensable for Wnt Pathway-Specific and Other Intestinal Epithelial Functions

Abstract

Methylation of H3K79 is associated with chromatin at expressed genes, though it is unclear if this histone modification is required for transcription of all genes. Recent studies suggest that Wnt-responsive genes depend particularly on H3K79 methylation, which is catalyzed by the methyltransferase DOT1L. Human leukemias carrying MLL gene rearrangements show DOT1L-mediated H3K79 methylation and aberrant expression of leukemogenic genes. DOT1L inhibitors reverse these effects, but their clinical use is potentially limited by toxicity in Wnt-dependent tissues such as intestinal epithelium. Genome-wide positioning of the H3K79me2 mark in Lgr5⁺ mouse intestinal stem cells and mature intestinal villus epithelium correlated with expression levels of all transcripts and not with Wnt-responsive genes per se. Selective Dot1l disruption in Lgr5⁺ stem cells or in whole intestinal epithelium eliminated H3K79me2 from the respective compartments, allowing genetic evaluation of DOT1L requirements. The absence of methylated H3K79 did not impair health, intestinal homeostasis, or expression of Wnt target genes in crypt epithelium for up to 4 months, despite increased crypt cell apoptosis. Global transcript profiles in Dot1l-null cells were barely altered. Thus, H3K79 methylation is not essential for transcription of Wnt-responsive or other intestinal genes, and intestinal toxicity is not imperative when DOT1L is rendered inactive in vivo.

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SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.01463-12.

ACKNOWLEDGMENTS

This work was supported by National Institutes of Health grants R01DK082889 (R.A.S.), R01CA140575 (S.A.A.), K01DK088868 (M.V.), RC2CA148222 (R.A.S. and S.A.A.), and P50CA127003.

We thank Sylvie Robine for gifting Villin-Cre^ER transgenic mice and Myles Brown for helpful discussions.

Author contributions are as follows. L.-L.H. contributed to the study design, conducting of experiments, data analysis, and editing of the manuscript. A.S. and S.A.A. contributed to the study design, data analysis, and editing of the manuscript. M.V. and K.M.B. contributed to conducting of experiments. R.A.S. contributed to the study design and supervision, data analysis, and writing and editing of the manuscript.

We declare that we have no conflicts of interest.