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DNMT1 maintains progenitor function in self-renewing somatic tissue.

Sen GL, Reuter JA, Webster DE, Zhu L, Khavari PA - Nature (2010)

Bottom Line: DNMT1 protein was found enriched in undifferentiated cells, where it was required to retain proliferative stamina and suppress differentiation.Genome-wide analysis showed that a significant portion of epidermal differentiation gene promoters were methylated in self-renewing conditions but were subsequently demethylated during differentiation.These data demonstrate that proteins involved in the dynamic regulation of DNA methylation patterns are required for progenitor maintenance and self-renewal in mammalian somatic tissue.

View Article: PubMed Central - PubMed

Affiliation: Programs in Epithelial Biology and Cancer Biology and the Stanford Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Stanford, California 94305, USA.

ABSTRACT
Progenitor cells maintain self-renewing tissues throughout life by sustaining their capacity for proliferation while suppressing cell cycle exit and terminal differentiation. DNA methylation provides a potential epigenetic mechanism for the cellular memory needed to preserve the somatic progenitor state through repeated cell divisions. DNA methyltransferase 1 (DNMT1) maintains DNA methylation patterns after cellular replication. Although dispensable for embryonic stem cell maintenance, the role for DNMT1 in maintaining the progenitor state in constantly replenished somatic tissues, such as mammalian epidermis, is unclear. Here we show that DNMT1 is essential for epidermal progenitor cell function. DNMT1 protein was found enriched in undifferentiated cells, where it was required to retain proliferative stamina and suppress differentiation. In tissue, DNMT1 depletion led to exit from the progenitor cell compartment, premature differentiation and eventual tissue loss. Genome-wide analysis showed that a significant portion of epidermal differentiation gene promoters were methylated in self-renewing conditions but were subsequently demethylated during differentiation. Furthermore, UHRF1 (refs 9, 10), a component of the DNA methylation machinery that targets DNMT1 to hemi-methylated DNA, is also necessary to suppress premature differentiation and sustain proliferation. In contrast, Gadd45A and B, which promote active DNA demethylation, are required for full epidermal differentiation gene induction. These data demonstrate that proteins involved in the dynamic regulation of DNA methylation patterns are required for progenitor maintenance and self-renewal in mammalian somatic tissue.

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DNMT1 is down-regulated during epidermal differentiationa, Microarray analysis characterizing genes altered during calcium-induced differentiation (genes repressed ≥2 fold are shown in green). b, c, Time course of DNMT1 down-regulation after induction of differentiation on the mRNA and protein level; error bars=s.d., n=3. d, DNMT1 protein distribution in adult human epidermis. DNMT1 (orange), differentiation keratin 1 (K1: green), Hoechst nuclear stain (blue); scale bar=30μm, dotted line denotes basement membrane.
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Figure 1: DNMT1 is down-regulated during epidermal differentiationa, Microarray analysis characterizing genes altered during calcium-induced differentiation (genes repressed ≥2 fold are shown in green). b, c, Time course of DNMT1 down-regulation after induction of differentiation on the mRNA and protein level; error bars=s.d., n=3. d, DNMT1 protein distribution in adult human epidermis. DNMT1 (orange), differentiation keratin 1 (K1: green), Hoechst nuclear stain (blue); scale bar=30μm, dotted line denotes basement membrane.

Mentions: In self-renewing mammalian epithelial tissues, which are the sites of most human malignancies14, the basis for repressed differentiation in somatic stem cells is unclear. Epigenetic gene silencers, such as DNMT1,4 may help preserve progenitor gene expression patterns through repeated cell divisions. Loss of function studies have demonstrated the importance of DNMT1 for imprinting, embryogenesis, and tumorigenesis15. DNMT1 knockout mice display delayed development and lethality by mid-gestation, hindering analysis of the function of DNMT1 in self-renewing epithelia, such as epidermis7,16. In epidermis, undifferentiated progenitor cells residing in the basement membrane-bound basal layer undergo cell cycle arrest, outward migration, and terminal differentiation to generate the cutaneous permeability barrier. Consistent with a role in this process, DNMT1 transcript and protein were repressed upon calcium-induced differentiation of human keratinocytes in culture (Fig. 1a-c, Supplementary Table 1). DNMT1 protein was mainly confined to cells of the basal layer of adult human epidermal tissue and was absent in outer differentiated layers (Fig. 1d). Thus, DNMT1 is expressed in epidermal progenitor-containing cell populations and is lost during differentiation.


DNMT1 maintains progenitor function in self-renewing somatic tissue.

Sen GL, Reuter JA, Webster DE, Zhu L, Khavari PA - Nature (2010)

DNMT1 is down-regulated during epidermal differentiationa, Microarray analysis characterizing genes altered during calcium-induced differentiation (genes repressed ≥2 fold are shown in green). b, c, Time course of DNMT1 down-regulation after induction of differentiation on the mRNA and protein level; error bars=s.d., n=3. d, DNMT1 protein distribution in adult human epidermis. DNMT1 (orange), differentiation keratin 1 (K1: green), Hoechst nuclear stain (blue); scale bar=30μm, dotted line denotes basement membrane.
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Related In: Results  -  Collection

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Figure 1: DNMT1 is down-regulated during epidermal differentiationa, Microarray analysis characterizing genes altered during calcium-induced differentiation (genes repressed ≥2 fold are shown in green). b, c, Time course of DNMT1 down-regulation after induction of differentiation on the mRNA and protein level; error bars=s.d., n=3. d, DNMT1 protein distribution in adult human epidermis. DNMT1 (orange), differentiation keratin 1 (K1: green), Hoechst nuclear stain (blue); scale bar=30μm, dotted line denotes basement membrane.
Mentions: In self-renewing mammalian epithelial tissues, which are the sites of most human malignancies14, the basis for repressed differentiation in somatic stem cells is unclear. Epigenetic gene silencers, such as DNMT1,4 may help preserve progenitor gene expression patterns through repeated cell divisions. Loss of function studies have demonstrated the importance of DNMT1 for imprinting, embryogenesis, and tumorigenesis15. DNMT1 knockout mice display delayed development and lethality by mid-gestation, hindering analysis of the function of DNMT1 in self-renewing epithelia, such as epidermis7,16. In epidermis, undifferentiated progenitor cells residing in the basement membrane-bound basal layer undergo cell cycle arrest, outward migration, and terminal differentiation to generate the cutaneous permeability barrier. Consistent with a role in this process, DNMT1 transcript and protein were repressed upon calcium-induced differentiation of human keratinocytes in culture (Fig. 1a-c, Supplementary Table 1). DNMT1 protein was mainly confined to cells of the basal layer of adult human epidermal tissue and was absent in outer differentiated layers (Fig. 1d). Thus, DNMT1 is expressed in epidermal progenitor-containing cell populations and is lost during differentiation.

Bottom Line: DNMT1 protein was found enriched in undifferentiated cells, where it was required to retain proliferative stamina and suppress differentiation.Genome-wide analysis showed that a significant portion of epidermal differentiation gene promoters were methylated in self-renewing conditions but were subsequently demethylated during differentiation.These data demonstrate that proteins involved in the dynamic regulation of DNA methylation patterns are required for progenitor maintenance and self-renewal in mammalian somatic tissue.

View Article: PubMed Central - PubMed

Affiliation: Programs in Epithelial Biology and Cancer Biology and the Stanford Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Stanford, California 94305, USA.

ABSTRACT
Progenitor cells maintain self-renewing tissues throughout life by sustaining their capacity for proliferation while suppressing cell cycle exit and terminal differentiation. DNA methylation provides a potential epigenetic mechanism for the cellular memory needed to preserve the somatic progenitor state through repeated cell divisions. DNA methyltransferase 1 (DNMT1) maintains DNA methylation patterns after cellular replication. Although dispensable for embryonic stem cell maintenance, the role for DNMT1 in maintaining the progenitor state in constantly replenished somatic tissues, such as mammalian epidermis, is unclear. Here we show that DNMT1 is essential for epidermal progenitor cell function. DNMT1 protein was found enriched in undifferentiated cells, where it was required to retain proliferative stamina and suppress differentiation. In tissue, DNMT1 depletion led to exit from the progenitor cell compartment, premature differentiation and eventual tissue loss. Genome-wide analysis showed that a significant portion of epidermal differentiation gene promoters were methylated in self-renewing conditions but were subsequently demethylated during differentiation. Furthermore, UHRF1 (refs 9, 10), a component of the DNA methylation machinery that targets DNMT1 to hemi-methylated DNA, is also necessary to suppress premature differentiation and sustain proliferation. In contrast, Gadd45A and B, which promote active DNA demethylation, are required for full epidermal differentiation gene induction. These data demonstrate that proteins involved in the dynamic regulation of DNA methylation patterns are required for progenitor maintenance and self-renewal in mammalian somatic tissue.

Show MeSH