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Perturbing the cellular levels of steroid receptor coactivator-2 impairs murine endometrial function.

Szwarc MM, Kommagani R, Jeong JW, Wu SP, Tsai SY, Tsai MJ, O'Malley BW, DeMayo FJ, Lydon JP - PLoS ONE (2014)

Bottom Line: As pleiotropic coregulators, members of the p160/steroid receptor coactivator (SRC) family control a broad spectrum of transcriptional responses that underpin a diverse array of physiological and pathophysiological processes.Because of their potent coregulator properties, strict controls on SRC expression levels are required to maintain normal tissue functionality.This deficiency is significant since SRC involvement in many of these disorders is based on unscheduled increases in the levels (rather than the absence) of SRC expression.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America.

ABSTRACT
As pleiotropic coregulators, members of the p160/steroid receptor coactivator (SRC) family control a broad spectrum of transcriptional responses that underpin a diverse array of physiological and pathophysiological processes. Because of their potent coregulator properties, strict controls on SRC expression levels are required to maintain normal tissue functionality. Accordingly, an unwarranted increase in the cellular levels of SRC members has been causally linked to the initiation and/or progression of a number of clinical disorders. Although knockout mouse models have underscored the critical non-redundant roles for each SRC member in vivo, there are surprisingly few mouse models that have been engineered to overexpress SRCs. This deficiency is significant since SRC involvement in many of these disorders is based on unscheduled increases in the levels (rather than the absence) of SRC expression. To address this deficiency, we used recent mouse technology that allows for the targeted expression of human SRC-2 in cells which express the progesterone receptor. Through cre-loxP recombination driven by the endogenous progesterone receptor promoter, a marked elevation in expression levels of human SRC-2 was achieved in endometrial cells that are positive for the progesterone receptor. As a result of this increase in coregulator expression, female mice are severely subfertile due to a dysfunctional uterus, which exhibits a hypersensitivity to estrogen exposure. Our findings strongly support the proposal from clinical observations that increased levels of SRC-2 are causal for a number of endometrial disorders which compromise fertility. Future studies will use this mouse model to decipher the molecular mechanisms that underpin the endometrial defect. We believe such mechanistic insight may provide new molecular descriptors for diagnosis, prognosis, and/or therapy in the clinical management of female infertility.

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The uterine epithelium of the SRC-2:OE mouse is significantly sensitive to estrogen exposure.(A) Schematic showing the E2 treatment protocol applied to SRC-2LSL and SRC-2:OE mouse groups. (B) Gross morphology of uteri from SRC-2LSL and SRC-2:OE mice following hormone treatment regimen shown in (A). Histogram on the right displays the ratio of uterine weight over body weight for SRC-2LSL and SRC-2:OE mice following vehicle or E2 treatment (***denotes p<0.001 (n = 5 mice per genotype/treatment)). (C) H&E stained uterine mid-horn sections from the SRC-2LSL and SRC-2:OE mice following E2 treatment; white arrowhead shows enlarged endometrial glands; scale bar in top panel applies to bottom panel. (D) Top left panel shows low power magnification image of the uterine mid-section of the SRC-2:OE mouse following E2 treatment stained for the myc-tag (a serial section of H&E stained section shown in bottom panel in (C)). Right top panel is a high power magnification image demarcated by a red box in the top left panel. Two bottom panels are higher power magnification images shown in two top panels; LE, GE, and S denote luminal epithelium, glandular epithelium, and stroma respectively. Scale bar in bottom left panel applies to bottom right panel. (E) High power magnification images of uterine sections stained for BrdU incorporation from SRC-2LSL and SRC-2:OE mice following E2 treatment. Scale bar in top left panel applies to all panels. Histogram in left panel displays the percentage positive for BrdU incorporation in the glandular epithelium of uteri from the SRC-2LSL and SRC-2:OE mouse groups following vehicle or E2 treatment (***denotes p<0.001 (n = 5 mice per genotype/treatment)).
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pone-0098664-g008: The uterine epithelium of the SRC-2:OE mouse is significantly sensitive to estrogen exposure.(A) Schematic showing the E2 treatment protocol applied to SRC-2LSL and SRC-2:OE mouse groups. (B) Gross morphology of uteri from SRC-2LSL and SRC-2:OE mice following hormone treatment regimen shown in (A). Histogram on the right displays the ratio of uterine weight over body weight for SRC-2LSL and SRC-2:OE mice following vehicle or E2 treatment (***denotes p<0.001 (n = 5 mice per genotype/treatment)). (C) H&E stained uterine mid-horn sections from the SRC-2LSL and SRC-2:OE mice following E2 treatment; white arrowhead shows enlarged endometrial glands; scale bar in top panel applies to bottom panel. (D) Top left panel shows low power magnification image of the uterine mid-section of the SRC-2:OE mouse following E2 treatment stained for the myc-tag (a serial section of H&E stained section shown in bottom panel in (C)). Right top panel is a high power magnification image demarcated by a red box in the top left panel. Two bottom panels are higher power magnification images shown in two top panels; LE, GE, and S denote luminal epithelium, glandular epithelium, and stroma respectively. Scale bar in bottom left panel applies to bottom right panel. (E) High power magnification images of uterine sections stained for BrdU incorporation from SRC-2LSL and SRC-2:OE mice following E2 treatment. Scale bar in top left panel applies to all panels. Histogram in left panel displays the percentage positive for BrdU incorporation in the glandular epithelium of uteri from the SRC-2LSL and SRC-2:OE mouse groups following vehicle or E2 treatment (***denotes p<0.001 (n = 5 mice per genotype/treatment)).

Mentions: Because the luminal epithelium in the stimulated uterine horn of the SRC-2:OE mouse continues to proliferate following a E2P4 hormone treatment protocol used to elicit decidualization (Fig. 7), we asked whether the SRC-2:OE endometrial epithelium is more sensitive to acute E2 exposure than the endometrial epithelium of the SRC-2LSL sibling. An answer to this question also may explain why the endometrial epithelium of the intact SRC-2:OE mouse registers a moderately higher proliferative response than that of the SRC-2LSL sibling (Fig. 4 and Figures S2 and 4). Using a modification of an E2 treatment protocol applied to the ovariectomized mouse [56] (Fig. 8A), the SRC-2LSL and SRC-2:OE endometria were assessed at both the gross and cellular level in terms of responsiveness to E2 exposure. At the gross morphological level, Fig. 8B clearly shows that the SRC-2:OE uterus exhibits a significantly greater uterotrophic response (i.e. an increase in uterine weight due to water imbibition and epithelial proliferation [56]) to E2 administration as compared to the SRC-2LSL control. Histological analysis (H&E as well as Myc-tag staining) of transverse sections of representative mid-uterine horns from the SRC-2:OE and the SRC-2LSL mouse following E2 treatment, clearly shows that the SRC-2:OE endometrium exhibits a more striking uterotrophic response, especially in terms of the size and number of hyperplastic epithelial glands, many of which develop into hemorrhagic cysts (Fig. 8C and D). Not surprisingly, immunohistochemical analysis for BrdU incorporation reveals that the endometrial luminal and glandular epithelium of the SRC-2:OE mouse exhibits a significant increase in the number of cells scoring positive for proliferation as compared to the similarly treated SRC-2LSL control mouse (Fig. 8E). These results support the proposal that increasing the levels of SRC-2 enhances E2-driven epithelial proliferation in the mouse endometrium, which may explain the subfertility defect exhibited by the SRC-2:OE mouse at the cellular level. Future studies will entail using the SRC-2:OE mouse model to define the molecular mechanisms that are responsible for the endometrial dysfunctional response due to SRC-2 overexpression.


Perturbing the cellular levels of steroid receptor coactivator-2 impairs murine endometrial function.

Szwarc MM, Kommagani R, Jeong JW, Wu SP, Tsai SY, Tsai MJ, O'Malley BW, DeMayo FJ, Lydon JP - PLoS ONE (2014)

The uterine epithelium of the SRC-2:OE mouse is significantly sensitive to estrogen exposure.(A) Schematic showing the E2 treatment protocol applied to SRC-2LSL and SRC-2:OE mouse groups. (B) Gross morphology of uteri from SRC-2LSL and SRC-2:OE mice following hormone treatment regimen shown in (A). Histogram on the right displays the ratio of uterine weight over body weight for SRC-2LSL and SRC-2:OE mice following vehicle or E2 treatment (***denotes p<0.001 (n = 5 mice per genotype/treatment)). (C) H&E stained uterine mid-horn sections from the SRC-2LSL and SRC-2:OE mice following E2 treatment; white arrowhead shows enlarged endometrial glands; scale bar in top panel applies to bottom panel. (D) Top left panel shows low power magnification image of the uterine mid-section of the SRC-2:OE mouse following E2 treatment stained for the myc-tag (a serial section of H&E stained section shown in bottom panel in (C)). Right top panel is a high power magnification image demarcated by a red box in the top left panel. Two bottom panels are higher power magnification images shown in two top panels; LE, GE, and S denote luminal epithelium, glandular epithelium, and stroma respectively. Scale bar in bottom left panel applies to bottom right panel. (E) High power magnification images of uterine sections stained for BrdU incorporation from SRC-2LSL and SRC-2:OE mice following E2 treatment. Scale bar in top left panel applies to all panels. Histogram in left panel displays the percentage positive for BrdU incorporation in the glandular epithelium of uteri from the SRC-2LSL and SRC-2:OE mouse groups following vehicle or E2 treatment (***denotes p<0.001 (n = 5 mice per genotype/treatment)).
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4048228&req=5

pone-0098664-g008: The uterine epithelium of the SRC-2:OE mouse is significantly sensitive to estrogen exposure.(A) Schematic showing the E2 treatment protocol applied to SRC-2LSL and SRC-2:OE mouse groups. (B) Gross morphology of uteri from SRC-2LSL and SRC-2:OE mice following hormone treatment regimen shown in (A). Histogram on the right displays the ratio of uterine weight over body weight for SRC-2LSL and SRC-2:OE mice following vehicle or E2 treatment (***denotes p<0.001 (n = 5 mice per genotype/treatment)). (C) H&E stained uterine mid-horn sections from the SRC-2LSL and SRC-2:OE mice following E2 treatment; white arrowhead shows enlarged endometrial glands; scale bar in top panel applies to bottom panel. (D) Top left panel shows low power magnification image of the uterine mid-section of the SRC-2:OE mouse following E2 treatment stained for the myc-tag (a serial section of H&E stained section shown in bottom panel in (C)). Right top panel is a high power magnification image demarcated by a red box in the top left panel. Two bottom panels are higher power magnification images shown in two top panels; LE, GE, and S denote luminal epithelium, glandular epithelium, and stroma respectively. Scale bar in bottom left panel applies to bottom right panel. (E) High power magnification images of uterine sections stained for BrdU incorporation from SRC-2LSL and SRC-2:OE mice following E2 treatment. Scale bar in top left panel applies to all panels. Histogram in left panel displays the percentage positive for BrdU incorporation in the glandular epithelium of uteri from the SRC-2LSL and SRC-2:OE mouse groups following vehicle or E2 treatment (***denotes p<0.001 (n = 5 mice per genotype/treatment)).
Mentions: Because the luminal epithelium in the stimulated uterine horn of the SRC-2:OE mouse continues to proliferate following a E2P4 hormone treatment protocol used to elicit decidualization (Fig. 7), we asked whether the SRC-2:OE endometrial epithelium is more sensitive to acute E2 exposure than the endometrial epithelium of the SRC-2LSL sibling. An answer to this question also may explain why the endometrial epithelium of the intact SRC-2:OE mouse registers a moderately higher proliferative response than that of the SRC-2LSL sibling (Fig. 4 and Figures S2 and 4). Using a modification of an E2 treatment protocol applied to the ovariectomized mouse [56] (Fig. 8A), the SRC-2LSL and SRC-2:OE endometria were assessed at both the gross and cellular level in terms of responsiveness to E2 exposure. At the gross morphological level, Fig. 8B clearly shows that the SRC-2:OE uterus exhibits a significantly greater uterotrophic response (i.e. an increase in uterine weight due to water imbibition and epithelial proliferation [56]) to E2 administration as compared to the SRC-2LSL control. Histological analysis (H&E as well as Myc-tag staining) of transverse sections of representative mid-uterine horns from the SRC-2:OE and the SRC-2LSL mouse following E2 treatment, clearly shows that the SRC-2:OE endometrium exhibits a more striking uterotrophic response, especially in terms of the size and number of hyperplastic epithelial glands, many of which develop into hemorrhagic cysts (Fig. 8C and D). Not surprisingly, immunohistochemical analysis for BrdU incorporation reveals that the endometrial luminal and glandular epithelium of the SRC-2:OE mouse exhibits a significant increase in the number of cells scoring positive for proliferation as compared to the similarly treated SRC-2LSL control mouse (Fig. 8E). These results support the proposal that increasing the levels of SRC-2 enhances E2-driven epithelial proliferation in the mouse endometrium, which may explain the subfertility defect exhibited by the SRC-2:OE mouse at the cellular level. Future studies will entail using the SRC-2:OE mouse model to define the molecular mechanisms that are responsible for the endometrial dysfunctional response due to SRC-2 overexpression.

Bottom Line: As pleiotropic coregulators, members of the p160/steroid receptor coactivator (SRC) family control a broad spectrum of transcriptional responses that underpin a diverse array of physiological and pathophysiological processes.Because of their potent coregulator properties, strict controls on SRC expression levels are required to maintain normal tissue functionality.This deficiency is significant since SRC involvement in many of these disorders is based on unscheduled increases in the levels (rather than the absence) of SRC expression.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America.

ABSTRACT
As pleiotropic coregulators, members of the p160/steroid receptor coactivator (SRC) family control a broad spectrum of transcriptional responses that underpin a diverse array of physiological and pathophysiological processes. Because of their potent coregulator properties, strict controls on SRC expression levels are required to maintain normal tissue functionality. Accordingly, an unwarranted increase in the cellular levels of SRC members has been causally linked to the initiation and/or progression of a number of clinical disorders. Although knockout mouse models have underscored the critical non-redundant roles for each SRC member in vivo, there are surprisingly few mouse models that have been engineered to overexpress SRCs. This deficiency is significant since SRC involvement in many of these disorders is based on unscheduled increases in the levels (rather than the absence) of SRC expression. To address this deficiency, we used recent mouse technology that allows for the targeted expression of human SRC-2 in cells which express the progesterone receptor. Through cre-loxP recombination driven by the endogenous progesterone receptor promoter, a marked elevation in expression levels of human SRC-2 was achieved in endometrial cells that are positive for the progesterone receptor. As a result of this increase in coregulator expression, female mice are severely subfertile due to a dysfunctional uterus, which exhibits a hypersensitivity to estrogen exposure. Our findings strongly support the proposal from clinical observations that increased levels of SRC-2 are causal for a number of endometrial disorders which compromise fertility. Future studies will use this mouse model to decipher the molecular mechanisms that underpin the endometrial defect. We believe such mechanistic insight may provide new molecular descriptors for diagnosis, prognosis, and/or therapy in the clinical management of female infertility.

Show MeSH
Related in: MedlinePlus