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The histone H3K79 methyltransferase Dot1L is essential for mammalian development and heterochromatin structure.

Jones B, Su H, Bhat A, Lei H, Bajko J, Hevi S, Baltus GA, Kadam S, Zhai H, Valdez R, Gonzalo S, Zhang Y, Li E, Chen T - PLoS Genet. (2008)

Bottom Line: Dot1L-deficient ES cells show global loss of H3K79 methylation as well as reduced levels of heterochromatic marks (H3K9 di-methylation and H4K20 tri-methylation) at centromeres and telomeres.These changes are accompanied by aneuploidy, telomere elongation, and proliferation defects.Taken together, these results indicate that Dot1L and H3K79 methylation play important roles in heterochromatin formation and in embryonic development.

View Article: PubMed Central - PubMed

Affiliation: Epigenetics Program, Novartis Institutes for Biomedical Research, Cambridge, Massachusetts, United States of America.

ABSTRACT
Dot1 is an evolutionarily conserved histone methyltransferase specific for lysine 79 of histone H3 (H3K79). In Saccharomyces cerevisiae, Dot1-mediated H3K79 methylation is associated with telomere silencing, meiotic checkpoint control, and DNA damage response. The biological function of H3K79 methylation in mammals, however, remains poorly understood. Using gene targeting, we generated mice deficient for Dot1L, the murine Dot1 homologue. Dot1L-deficient embryos show multiple developmental abnormalities, including growth impairment, angiogenesis defects in the yolk sac, and cardiac dilation, and die between 9.5 and 10.5 days post coitum. To gain insights into the cellular function of Dot1L, we derived embryonic stem (ES) cells from Dot1L mutant blastocysts. Dot1L-deficient ES cells show global loss of H3K79 methylation as well as reduced levels of heterochromatic marks (H3K9 di-methylation and H4K20 tri-methylation) at centromeres and telomeres. These changes are accompanied by aneuploidy, telomere elongation, and proliferation defects. Taken together, these results indicate that Dot1L and H3K79 methylation play important roles in heterochromatin formation and in embryonic development.

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Essential role for Dot1L in mouse embryonic development.(A) A representative X-gal stained 7.5-dpc Dot1L3lox/+ embryo demonstrating ubiquitous Dot1L transcription throughout the embryo. (B) A representative X-gal stained 9.5-dpc Dot1L3lox/+ embryo demonstrating ubiquitous Dot1L transcription throughout the embryo with elevated Dot1L expression in the indicated regions. (C) A representative X-gal stained 9.5-dpc Dot1L3lox/+ yolk sac demonstrating Dot1L transcription in visceral endoderm, visceral mesoderm, and primitive erythrocytes. (D) Representative pictures of 9.5-dpc Dot1L1lox/+ and Dot1L1lox/1lox embryos. Dot1L1lox/+ embryos (left) were indistinguishable from wild-type embryos. Most Dot1L1lox/1lox embryos were undersized, had an enlarged heart (cardiac dilation) and stunted tail (center), while approximately 15% exhibited developmental arrest at E8.5 (right). (E) Representative pictures of a 10.5-dpc Dot1L1lox/1lox embryo (right) and a heterozygous littermate (left). (F) Representative pictures showing the yolk sac vasculature of 9.5-dpc Dot1L1lox/+ (left) and Dot1L1lox/1lox (right) embryos. The vasculature of the Dot1L1lox/1lox yolk sac is thinner and less organized than that of the heterozygous littermate.
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pgen-1000190-g002: Essential role for Dot1L in mouse embryonic development.(A) A representative X-gal stained 7.5-dpc Dot1L3lox/+ embryo demonstrating ubiquitous Dot1L transcription throughout the embryo. (B) A representative X-gal stained 9.5-dpc Dot1L3lox/+ embryo demonstrating ubiquitous Dot1L transcription throughout the embryo with elevated Dot1L expression in the indicated regions. (C) A representative X-gal stained 9.5-dpc Dot1L3lox/+ yolk sac demonstrating Dot1L transcription in visceral endoderm, visceral mesoderm, and primitive erythrocytes. (D) Representative pictures of 9.5-dpc Dot1L1lox/+ and Dot1L1lox/1lox embryos. Dot1L1lox/+ embryos (left) were indistinguishable from wild-type embryos. Most Dot1L1lox/1lox embryos were undersized, had an enlarged heart (cardiac dilation) and stunted tail (center), while approximately 15% exhibited developmental arrest at E8.5 (right). (E) Representative pictures of a 10.5-dpc Dot1L1lox/1lox embryo (right) and a heterozygous littermate (left). (F) Representative pictures showing the yolk sac vasculature of 9.5-dpc Dot1L1lox/+ (left) and Dot1L1lox/1lox (right) embryos. The vasculature of the Dot1L1lox/1lox yolk sac is thinner and less organized than that of the heterozygous littermate.

Mentions: We first determined the expression of Dot1L during embryonic development, taking advantage of the fact that cells containing the Dot1L3lox allele express lacZ under the control of the endogenous Dot1L promoter. We conducted X-gal staining on Dot1L3lox/+ heterozygous embryos and wild-type littermates at different stages of development. Dot1L expression is ubiquitous as early as 7.5-dpc (the earliest time point tested, Figure 2A). At 9.5-dpc, Dot1L expression remains ubiquitous and areas of elevated expression are apparent. Tissues that demonstrate high levels of lacZ staining include the optic vesicle, the first branchial arch, the limb buds, the heart, the otic pit, and the neural ectoderm (Figure 2B). Dot1L is also expressed at high levels in extra-embryonic tissues, including the visceral endoderm and visceral mesoderm of the yolk sac, and in primitive erythrocytes (Figure 2C). Similar lacZ staining patterns are observed in embryos harvested at 10.5-dpc, 11.5-dpc, and 12.5-dpc (data not shown), suggesting that Dot1L is broadly expressed during embryonic development.


The histone H3K79 methyltransferase Dot1L is essential for mammalian development and heterochromatin structure.

Jones B, Su H, Bhat A, Lei H, Bajko J, Hevi S, Baltus GA, Kadam S, Zhai H, Valdez R, Gonzalo S, Zhang Y, Li E, Chen T - PLoS Genet. (2008)

Essential role for Dot1L in mouse embryonic development.(A) A representative X-gal stained 7.5-dpc Dot1L3lox/+ embryo demonstrating ubiquitous Dot1L transcription throughout the embryo. (B) A representative X-gal stained 9.5-dpc Dot1L3lox/+ embryo demonstrating ubiquitous Dot1L transcription throughout the embryo with elevated Dot1L expression in the indicated regions. (C) A representative X-gal stained 9.5-dpc Dot1L3lox/+ yolk sac demonstrating Dot1L transcription in visceral endoderm, visceral mesoderm, and primitive erythrocytes. (D) Representative pictures of 9.5-dpc Dot1L1lox/+ and Dot1L1lox/1lox embryos. Dot1L1lox/+ embryos (left) were indistinguishable from wild-type embryos. Most Dot1L1lox/1lox embryos were undersized, had an enlarged heart (cardiac dilation) and stunted tail (center), while approximately 15% exhibited developmental arrest at E8.5 (right). (E) Representative pictures of a 10.5-dpc Dot1L1lox/1lox embryo (right) and a heterozygous littermate (left). (F) Representative pictures showing the yolk sac vasculature of 9.5-dpc Dot1L1lox/+ (left) and Dot1L1lox/1lox (right) embryos. The vasculature of the Dot1L1lox/1lox yolk sac is thinner and less organized than that of the heterozygous littermate.
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Related In: Results  -  Collection

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pgen-1000190-g002: Essential role for Dot1L in mouse embryonic development.(A) A representative X-gal stained 7.5-dpc Dot1L3lox/+ embryo demonstrating ubiquitous Dot1L transcription throughout the embryo. (B) A representative X-gal stained 9.5-dpc Dot1L3lox/+ embryo demonstrating ubiquitous Dot1L transcription throughout the embryo with elevated Dot1L expression in the indicated regions. (C) A representative X-gal stained 9.5-dpc Dot1L3lox/+ yolk sac demonstrating Dot1L transcription in visceral endoderm, visceral mesoderm, and primitive erythrocytes. (D) Representative pictures of 9.5-dpc Dot1L1lox/+ and Dot1L1lox/1lox embryos. Dot1L1lox/+ embryos (left) were indistinguishable from wild-type embryos. Most Dot1L1lox/1lox embryos were undersized, had an enlarged heart (cardiac dilation) and stunted tail (center), while approximately 15% exhibited developmental arrest at E8.5 (right). (E) Representative pictures of a 10.5-dpc Dot1L1lox/1lox embryo (right) and a heterozygous littermate (left). (F) Representative pictures showing the yolk sac vasculature of 9.5-dpc Dot1L1lox/+ (left) and Dot1L1lox/1lox (right) embryos. The vasculature of the Dot1L1lox/1lox yolk sac is thinner and less organized than that of the heterozygous littermate.
Mentions: We first determined the expression of Dot1L during embryonic development, taking advantage of the fact that cells containing the Dot1L3lox allele express lacZ under the control of the endogenous Dot1L promoter. We conducted X-gal staining on Dot1L3lox/+ heterozygous embryos and wild-type littermates at different stages of development. Dot1L expression is ubiquitous as early as 7.5-dpc (the earliest time point tested, Figure 2A). At 9.5-dpc, Dot1L expression remains ubiquitous and areas of elevated expression are apparent. Tissues that demonstrate high levels of lacZ staining include the optic vesicle, the first branchial arch, the limb buds, the heart, the otic pit, and the neural ectoderm (Figure 2B). Dot1L is also expressed at high levels in extra-embryonic tissues, including the visceral endoderm and visceral mesoderm of the yolk sac, and in primitive erythrocytes (Figure 2C). Similar lacZ staining patterns are observed in embryos harvested at 10.5-dpc, 11.5-dpc, and 12.5-dpc (data not shown), suggesting that Dot1L is broadly expressed during embryonic development.

Bottom Line: Dot1L-deficient ES cells show global loss of H3K79 methylation as well as reduced levels of heterochromatic marks (H3K9 di-methylation and H4K20 tri-methylation) at centromeres and telomeres.These changes are accompanied by aneuploidy, telomere elongation, and proliferation defects.Taken together, these results indicate that Dot1L and H3K79 methylation play important roles in heterochromatin formation and in embryonic development.

View Article: PubMed Central - PubMed

Affiliation: Epigenetics Program, Novartis Institutes for Biomedical Research, Cambridge, Massachusetts, United States of America.

ABSTRACT
Dot1 is an evolutionarily conserved histone methyltransferase specific for lysine 79 of histone H3 (H3K79). In Saccharomyces cerevisiae, Dot1-mediated H3K79 methylation is associated with telomere silencing, meiotic checkpoint control, and DNA damage response. The biological function of H3K79 methylation in mammals, however, remains poorly understood. Using gene targeting, we generated mice deficient for Dot1L, the murine Dot1 homologue. Dot1L-deficient embryos show multiple developmental abnormalities, including growth impairment, angiogenesis defects in the yolk sac, and cardiac dilation, and die between 9.5 and 10.5 days post coitum. To gain insights into the cellular function of Dot1L, we derived embryonic stem (ES) cells from Dot1L mutant blastocysts. Dot1L-deficient ES cells show global loss of H3K79 methylation as well as reduced levels of heterochromatic marks (H3K9 di-methylation and H4K20 tri-methylation) at centromeres and telomeres. These changes are accompanied by aneuploidy, telomere elongation, and proliferation defects. Taken together, these results indicate that Dot1L and H3K79 methylation play important roles in heterochromatin formation and in embryonic development.

Show MeSH
Related in: MedlinePlus