Alex R Pinto

Publications (3)13.9 Total impact

• Article: Estrogen deficiency reversibly induces telomere shortening in mouse granulosa cells and ovarian aging in vivo.

  Sharyn Bayne, He Li, Margaret E E Jones, Alex R Pinto, Michelle van Sinderen, Ann Drummond, Evan R Simpson, Jun-Ping Liu
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  ABSTRACT: Estrogen is implicated as playing an important role in aging and tumorigenesis of estrogen responsive tissues; however the mechanisms underlying the mitogenic actions of estrogen are not fully understood. Here we report that estrogen deficiency in mice caused by targeted disruption of the aromatase gene results in a significant inhibition of telomerase maintenance of telomeres in mouse ovaries in a tissue-specific manner. The inhibition entails a significant shortening of telomeres and compromised proliferation in the follicular granulosa cell compartment of ovary. Gene expression analysis showed decreased levels of proto-oncogene c-Myc and the telomerase catalytic subunit, telomerase reverse transcriptase (TERT), in response to estrogen deficiency. Estrogen replacement therapy led to increases in TERT gene expression, telomerase activity, telomere length and ovarian tissue growth, thereby reinstating ovary development to normal in four weeks. Our data demonstrate for the first time that telomere maintenance is the primary mechanism mediating the mitogenic effect of estrogen on ovarian granulosa cell proliferation by upregulating the genes of c-Myc and TERT in vivo. Estrogen deficiency or over-activity may cause ovarian tissue aging or tumorigenesis, respectively, through estrogen regulation of telomere remodeling.
  Protein & Cell 04/2011; 2(4):333-46.
• Article: Bone morphogenetic protein-7 induces telomerase inhibition, telomere shortening, breast cancer cell senescence, and death via Smad3.

  Lucy Cassar, Craig Nicholls, Alex R Pinto, He Li, Jun-Ping Liu
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  ABSTRACT: Human telomerase reverse transcriptase (hTERT) is central to maintain telomeres for continuous cell proliferation, but it remains unknown how extracellular cues regulate telomerase maintenance of telomeres. Here we report that the cytokine bone morphogenetic protein-7 (BMP7) induces Smad3 phosphorylation, nuclear translocation, and hTERT gene repression. BMP7 induces Smad3-dependent telomerase inhibition in a time- and concentration-dependent manner in breast cancer cells. Chronic exposure of breast cancer cells to BMP7 results in short telomeres, cell senescence, and apoptosis. Mutation of BMPRII receptor, but not TGFbetaRII, ACTRIIA, or ACTRIIB, blocked BMP7-induced repression of the hTERT gene promoter activity, leading to increased telomerase activity, lengthened telomeres, and continued cell proliferation. Expression of hTERT inhibits BMP7-induced breast cancer cell senescence and apoptosis. Thus, our data suggest that BMP7 induces breast cancer cell aging and death by a mechanism involving inhibition of telomerase activity and telomere maintenance via BMPRII receptor- and Smad3-mediated repression of the hTERT gene.
  The FASEB Journal 03/2009; 23(6):1880-92. · 5.71 Impact Factor
• Article: Estrogen deficiency leads to telomerase inhibition, telomere shortening and reduced cell proliferation in the adrenal gland of mice.

  Sharyn Bayne, Margaret Ee Jones, He Li, Alex R Pinto, Evan R Simpson, Jun-Ping Liu
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  ABSTRACT: Estrogen deficiency mediates aging, but the underlying mechanism remains to be fully determined. We report here that estrogen deficiency caused by targeted disruption of aromatase in mice results in significant inhibition of telomerase activity in the adrenal gland in vivo. Gene expression analysis showed that, in the absence of estrogen, telomerase reverse transcriptase (TERT) gene expression is reduced in association with compromised cell proliferation in the adrenal gland cortex and adrenal atrophy. Stem cells positive in c-kit are identified to populate in the parenchyma of adrenal cortex. Analysis of telomeres revealed that estrogen deficiency results in significantly shorter telomeres in the adrenal cortex than that in wild-type (WT) control mice. To further establish the causal effects of estrogen, we conducted an estrogen replacement therapy in these estrogen-deficient animals. Administration of estrogen for 3 weeks restores TERT gene expression, telomerase activity and cell proliferation in estrogen-deficient mice. Thus, our data show for the first time that estrogen deficiency causes inhibitions of TERT gene expression, telomerase activity, telomere maintenance, and cell proliferation in the adrenal gland of mice in vivo, suggesting that telomerase inhibition and telomere shortening may mediate cell proliferation arrest in the adrenal gland, thus contributing to estrogen deficiency-induced aging under physiological conditions.
  Cell Research 11/2008; 18(11):1141-50. · 8.19 Impact Factor