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TERT promotes epithelial proliferation through transcriptional control of a Myc- and Wnt-related developmental program.

Choi J, Southworth LK, Sarin KY, Venteicher AS, Ma W, Chang W, Cheung P, Jun S, Artandi MK, Shah N, Kim SK, Artandi SE - PLoS Genet. (2007)

Bottom Line: This role depends on its ability to synthesize telomere repeats in a manner dependent on the reverse transcriptase (RT) function of its protein component telomerase RT (TERT), as well as on a novel pathway whose mechanism is poorly understood.We show that TERT(ci) retains the full activities of wild-type TERT in enhancing keratinocyte proliferation in skin and in activating resting hair follicle stem cells, which triggers initiation of a new hair follicle growth phase and promotes hair synthesis.These data show that TERT controls tissue progenitor cells via transcriptional regulation of a developmental program converging on the Myc and Wnt pathways.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Stanford School of Medicine, Stanford, California, United States of America.

ABSTRACT
Telomerase serves a critical role in stem cell function and tissue homeostasis. This role depends on its ability to synthesize telomere repeats in a manner dependent on the reverse transcriptase (RT) function of its protein component telomerase RT (TERT), as well as on a novel pathway whose mechanism is poorly understood. Here, we use a TERT mutant lacking RT function (TERT(ci)) to study the mechanism of TERT action in mammalian skin, an ideal tissue for studying progenitor cell biology. We show that TERT(ci) retains the full activities of wild-type TERT in enhancing keratinocyte proliferation in skin and in activating resting hair follicle stem cells, which triggers initiation of a new hair follicle growth phase and promotes hair synthesis. To understand the nature of this RT-independent function for TERT, we studied the genome-wide transcriptional response to acute changes in TERT levels in mouse skin. We find that TERT facilitates activation of progenitor cells in the skin and hair follicle by triggering a rapid change in gene expression that significantly overlaps the program controlling natural hair follicle cycling in wild-type mice. Statistical comparisons to other microarray gene sets using pattern-matching algorithms revealed that the TERT transcriptional response strongly resembles those mediated by Myc and Wnt, two proteins intimately associated with stem cell function and cancer. These data show that TERT controls tissue progenitor cells via transcriptional regulation of a developmental program converging on the Myc and Wnt pathways.

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Validation of TERT-Regulated Genes by Quantitative RT-PCR(A–B) Representative TERT-activated genes (A) and TERT-repressed genes (B) associated with different functional categories were validated by real-time PCR. (TERT ON = Control 24-h timepoint; TERT OFF = 24 h after doxycycline treatment timepoint; n = 3. Error bars represent standard errors).(C) Semi-quantitative RT-PCR validation of some representative genes.(D) Detailed results of quantitative RT-PCR validation of TERT-regulated genes.
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pgen-0040010-g005: Validation of TERT-Regulated Genes by Quantitative RT-PCR(A–B) Representative TERT-activated genes (A) and TERT-repressed genes (B) associated with different functional categories were validated by real-time PCR. (TERT ON = Control 24-h timepoint; TERT OFF = 24 h after doxycycline treatment timepoint; n = 3. Error bars represent standard errors).(C) Semi-quantitative RT-PCR validation of some representative genes.(D) Detailed results of quantitative RT-PCR validation of TERT-regulated genes.

Mentions: To begin to understand the patterns of gene expression changes, we first classified TERT-regulated genes based on functional annotation [32]. TERT-activated genes consisted of three major categories, genes involved in development/morphogenesis (22.2%, 86/388), signal transduction (52.8%, 205/388), and cytoskeleton/membrane/cell-to-cell signaling (59.0%, 229/388) (Figure 4D). A number of TERT-activated genes were prominent members of the Wnt, Shh and BMP pathways, signaling cascades critical for hair follicle development and cycling. These include Bambi, Bmp8a, Ccnd2, Lef1, Nkd2, Smad7, Wnt5a, and Wnt11 (Figure 4F, colored in red). Other TERT-activated genes are not known to reside in these pathways, but have strong epidermal phenotypes in knockout or transgenic mice, including Cutl1, Dlx3, Fgf5, Foxq1, Kitl, Msx2, and Ovol1 (Figure 4F, colored in blue). Compared to TERT-activated genes, fewer TERT-repressed genes were associated with development/differentiation (8.0%, 19/238) and signal transduction (28.6%, 68/238), but a similar number were associated with cytoskeleton/membrane/cell-to-cell signaling (48.3%, 115/238) (Figure 4E and 4G). To validate our microarray results, we performed quantitative RT-PCR on 14 target genes derived from our gene expression profiling experiments. These candidate genes were chosen to represent each of the three functional categories assigned for TERT-regulated genes. Each of the 14 TERT-activated and TERT-repressed genes studied showed strong regulation by TERT withdrawal at 24 hours by real-time RT-PCR, results in close agreement with data from our microarray analysis (Figure 5). These data show that TERT controls the expression of critical regulators involved in epithelial development, signal transduction and cytoskeleton/cell adhesion.


TERT promotes epithelial proliferation through transcriptional control of a Myc- and Wnt-related developmental program.

Choi J, Southworth LK, Sarin KY, Venteicher AS, Ma W, Chang W, Cheung P, Jun S, Artandi MK, Shah N, Kim SK, Artandi SE - PLoS Genet. (2007)

Validation of TERT-Regulated Genes by Quantitative RT-PCR(A–B) Representative TERT-activated genes (A) and TERT-repressed genes (B) associated with different functional categories were validated by real-time PCR. (TERT ON = Control 24-h timepoint; TERT OFF = 24 h after doxycycline treatment timepoint; n = 3. Error bars represent standard errors).(C) Semi-quantitative RT-PCR validation of some representative genes.(D) Detailed results of quantitative RT-PCR validation of TERT-regulated genes.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2211538&req=5

pgen-0040010-g005: Validation of TERT-Regulated Genes by Quantitative RT-PCR(A–B) Representative TERT-activated genes (A) and TERT-repressed genes (B) associated with different functional categories were validated by real-time PCR. (TERT ON = Control 24-h timepoint; TERT OFF = 24 h after doxycycline treatment timepoint; n = 3. Error bars represent standard errors).(C) Semi-quantitative RT-PCR validation of some representative genes.(D) Detailed results of quantitative RT-PCR validation of TERT-regulated genes.
Mentions: To begin to understand the patterns of gene expression changes, we first classified TERT-regulated genes based on functional annotation [32]. TERT-activated genes consisted of three major categories, genes involved in development/morphogenesis (22.2%, 86/388), signal transduction (52.8%, 205/388), and cytoskeleton/membrane/cell-to-cell signaling (59.0%, 229/388) (Figure 4D). A number of TERT-activated genes were prominent members of the Wnt, Shh and BMP pathways, signaling cascades critical for hair follicle development and cycling. These include Bambi, Bmp8a, Ccnd2, Lef1, Nkd2, Smad7, Wnt5a, and Wnt11 (Figure 4F, colored in red). Other TERT-activated genes are not known to reside in these pathways, but have strong epidermal phenotypes in knockout or transgenic mice, including Cutl1, Dlx3, Fgf5, Foxq1, Kitl, Msx2, and Ovol1 (Figure 4F, colored in blue). Compared to TERT-activated genes, fewer TERT-repressed genes were associated with development/differentiation (8.0%, 19/238) and signal transduction (28.6%, 68/238), but a similar number were associated with cytoskeleton/membrane/cell-to-cell signaling (48.3%, 115/238) (Figure 4E and 4G). To validate our microarray results, we performed quantitative RT-PCR on 14 target genes derived from our gene expression profiling experiments. These candidate genes were chosen to represent each of the three functional categories assigned for TERT-regulated genes. Each of the 14 TERT-activated and TERT-repressed genes studied showed strong regulation by TERT withdrawal at 24 hours by real-time RT-PCR, results in close agreement with data from our microarray analysis (Figure 5). These data show that TERT controls the expression of critical regulators involved in epithelial development, signal transduction and cytoskeleton/cell adhesion.

Bottom Line: This role depends on its ability to synthesize telomere repeats in a manner dependent on the reverse transcriptase (RT) function of its protein component telomerase RT (TERT), as well as on a novel pathway whose mechanism is poorly understood.We show that TERT(ci) retains the full activities of wild-type TERT in enhancing keratinocyte proliferation in skin and in activating resting hair follicle stem cells, which triggers initiation of a new hair follicle growth phase and promotes hair synthesis.These data show that TERT controls tissue progenitor cells via transcriptional regulation of a developmental program converging on the Myc and Wnt pathways.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Stanford School of Medicine, Stanford, California, United States of America.

ABSTRACT
Telomerase serves a critical role in stem cell function and tissue homeostasis. This role depends on its ability to synthesize telomere repeats in a manner dependent on the reverse transcriptase (RT) function of its protein component telomerase RT (TERT), as well as on a novel pathway whose mechanism is poorly understood. Here, we use a TERT mutant lacking RT function (TERT(ci)) to study the mechanism of TERT action in mammalian skin, an ideal tissue for studying progenitor cell biology. We show that TERT(ci) retains the full activities of wild-type TERT in enhancing keratinocyte proliferation in skin and in activating resting hair follicle stem cells, which triggers initiation of a new hair follicle growth phase and promotes hair synthesis. To understand the nature of this RT-independent function for TERT, we studied the genome-wide transcriptional response to acute changes in TERT levels in mouse skin. We find that TERT facilitates activation of progenitor cells in the skin and hair follicle by triggering a rapid change in gene expression that significantly overlaps the program controlling natural hair follicle cycling in wild-type mice. Statistical comparisons to other microarray gene sets using pattern-matching algorithms revealed that the TERT transcriptional response strongly resembles those mediated by Myc and Wnt, two proteins intimately associated with stem cell function and cancer. These data show that TERT controls tissue progenitor cells via transcriptional regulation of a developmental program converging on the Myc and Wnt pathways.

Show MeSH
Related in: MedlinePlus