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Signal transducer and activator of transcription (Stat) 5 controls the proliferation and differentiation of mammary alveolar epithelium.

Miyoshi K, Shillingford JM, Smith GH, Grimm SL, Wagner KU, Oka T, Rosen JM, Robinson GW, Hennighausen L - J. Cell Biol. (2001)

Bottom Line: Stat5- mammary epithelium developed ducts but failed to form alveoli, and no milk protein gene expression was observed.Expression of NKCC1, an Na-K-Cl cotransporter characteristic for ductal epithelia, and ZO-1, a protein associated with tight junction, were maintained in the alveoli-like structures of PrlR- and Stat5- epithelia.These data demonstrate that signaling via the PrlR and Stat5 is critical for the proliferation and differentiation of mammary alveoli during pregnancy.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Genetics and Physiology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA. mammary@nih.gov

ABSTRACT
Functional development of mammary epithelium during pregnancy depends on prolactin signaling. However, the underlying molecular and cellular events are not fully understood. We examined the specific contributions of the prolactin receptor (PrlR) and the signal transducers and activators of transcription 5a and 5b (referred to as Stat5) in the formation and differentiation of mammary alveolar epithelium. PrlR- and Stat5- mammary epithelia were transplanted into wild-type hosts, and pregnancy-mediated development was investigated at a histological and molecular level. Stat5- mammary epithelium developed ducts but failed to form alveoli, and no milk protein gene expression was observed. In contrast, PrlR- epithelium formed alveoli-like structures with small open lumina. Electron microscopy revealed undifferentiated features of organelles and a perturbation of cell-cell contacts in PrlR- and Stat5- epithelia. Expression of NKCC1, an Na-K-Cl cotransporter characteristic for ductal epithelia, and ZO-1, a protein associated with tight junction, were maintained in the alveoli-like structures of PrlR- and Stat5- epithelia. In contrast, the Na-Pi cotransporter Npt2b, and the gap junction component connexin 32, usually expressed in secretory epithelia, were undetectable in PrlR- and Stat5- mice. These data demonstrate that signaling via the PrlR and Stat5 is critical for the proliferation and differentiation of mammary alveoli during pregnancy.

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Maintenance of ZO-1 expression but loss of Cx 32 expression. Immunohistochemical staining of ZO-1 (green) and E-cadherin (red) at parturition (A–C). Tight junctions (green dots) were present in PrlR- (A) and Stat5- (B) the same as in wild-type epithelium (C). Arrows point to alveoli-like structures of PrlR- and Stat5- epithelia. (D) RT-PCR analysis of Cx 32 mRNA. Total RNA from wild-type, Stat5-, and PrlR- transplanted epithelia at parturition was reverse transcribed, and the cDNA was subjected to PCR. Cx 32 cDNA was detected in wild-type but not in PrlR- or Stat5- samples. GAPDH levels were similar in all samples. M, marker.
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fig5: Maintenance of ZO-1 expression but loss of Cx 32 expression. Immunohistochemical staining of ZO-1 (green) and E-cadherin (red) at parturition (A–C). Tight junctions (green dots) were present in PrlR- (A) and Stat5- (B) the same as in wild-type epithelium (C). Arrows point to alveoli-like structures of PrlR- and Stat5- epithelia. (D) RT-PCR analysis of Cx 32 mRNA. Total RNA from wild-type, Stat5-, and PrlR- transplanted epithelia at parturition was reverse transcribed, and the cDNA was subjected to PCR. Cx 32 cDNA was detected in wild-type but not in PrlR- or Stat5- samples. GAPDH levels were similar in all samples. M, marker.

Mentions: Epithelial cells contact each other via tight and adherens junctions (Cereijido et al., 1998; Borrmann et al., 2000; Vasioukhin and Fuchs, 2001), which stabilize epithelial structures and determine their integrity. Further, these junctions are necessary to establish and maintain cell polarity (Knust, 2000; Vicente-Manzanares and Sanchez-Madrid, 2000) that permits vectorial secretion (Barcellos-Hoff et al., 1989). Fig. 4 D shows the morphological appearance of a tight junction complex between the apical poles of two individual secretory cells in wild-type epithelium. One of the most conspicuous features of the Stat5- epithelium was the lack of organized cell contacts. To identify possible causes for the lack of organized cell contacts we investigated the expression of zonula occludens (ZO)-1, a component of tight junctions. Tight junctions were identified in PrlR- and Stat5- epithelia (Fig. 4, E and F) and visualized by ZO-1 staining (Fig. 5, A and B). We further investigated the expression of connexin, a protein in the gap junction complex, in PrlR- and Stat5- epithelia. It has been demonstrated previously (Pozzi et al., 1995; Locke et al., 2000) that mouse mammary tissue expresses three connexin isoforms (Cx 43, Cx 26, and Cx 32), which we confirmed using reverse transcription (RT)-PCR analyses. Whereas Cx 32 mRNA was detected in wild-type epithelia at day 1 of lactation, we were unable to detect expression in PrlR- and Stat5- epithelia at parturition (Fig. 5 D).


Signal transducer and activator of transcription (Stat) 5 controls the proliferation and differentiation of mammary alveolar epithelium.

Miyoshi K, Shillingford JM, Smith GH, Grimm SL, Wagner KU, Oka T, Rosen JM, Robinson GW, Hennighausen L - J. Cell Biol. (2001)

Maintenance of ZO-1 expression but loss of Cx 32 expression. Immunohistochemical staining of ZO-1 (green) and E-cadherin (red) at parturition (A–C). Tight junctions (green dots) were present in PrlR- (A) and Stat5- (B) the same as in wild-type epithelium (C). Arrows point to alveoli-like structures of PrlR- and Stat5- epithelia. (D) RT-PCR analysis of Cx 32 mRNA. Total RNA from wild-type, Stat5-, and PrlR- transplanted epithelia at parturition was reverse transcribed, and the cDNA was subjected to PCR. Cx 32 cDNA was detected in wild-type but not in PrlR- or Stat5- samples. GAPDH levels were similar in all samples. M, marker.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2198867&req=5

fig5: Maintenance of ZO-1 expression but loss of Cx 32 expression. Immunohistochemical staining of ZO-1 (green) and E-cadherin (red) at parturition (A–C). Tight junctions (green dots) were present in PrlR- (A) and Stat5- (B) the same as in wild-type epithelium (C). Arrows point to alveoli-like structures of PrlR- and Stat5- epithelia. (D) RT-PCR analysis of Cx 32 mRNA. Total RNA from wild-type, Stat5-, and PrlR- transplanted epithelia at parturition was reverse transcribed, and the cDNA was subjected to PCR. Cx 32 cDNA was detected in wild-type but not in PrlR- or Stat5- samples. GAPDH levels were similar in all samples. M, marker.
Mentions: Epithelial cells contact each other via tight and adherens junctions (Cereijido et al., 1998; Borrmann et al., 2000; Vasioukhin and Fuchs, 2001), which stabilize epithelial structures and determine their integrity. Further, these junctions are necessary to establish and maintain cell polarity (Knust, 2000; Vicente-Manzanares and Sanchez-Madrid, 2000) that permits vectorial secretion (Barcellos-Hoff et al., 1989). Fig. 4 D shows the morphological appearance of a tight junction complex between the apical poles of two individual secretory cells in wild-type epithelium. One of the most conspicuous features of the Stat5- epithelium was the lack of organized cell contacts. To identify possible causes for the lack of organized cell contacts we investigated the expression of zonula occludens (ZO)-1, a component of tight junctions. Tight junctions were identified in PrlR- and Stat5- epithelia (Fig. 4, E and F) and visualized by ZO-1 staining (Fig. 5, A and B). We further investigated the expression of connexin, a protein in the gap junction complex, in PrlR- and Stat5- epithelia. It has been demonstrated previously (Pozzi et al., 1995; Locke et al., 2000) that mouse mammary tissue expresses three connexin isoforms (Cx 43, Cx 26, and Cx 32), which we confirmed using reverse transcription (RT)-PCR analyses. Whereas Cx 32 mRNA was detected in wild-type epithelia at day 1 of lactation, we were unable to detect expression in PrlR- and Stat5- epithelia at parturition (Fig. 5 D).

Bottom Line: Stat5- mammary epithelium developed ducts but failed to form alveoli, and no milk protein gene expression was observed.Expression of NKCC1, an Na-K-Cl cotransporter characteristic for ductal epithelia, and ZO-1, a protein associated with tight junction, were maintained in the alveoli-like structures of PrlR- and Stat5- epithelia.These data demonstrate that signaling via the PrlR and Stat5 is critical for the proliferation and differentiation of mammary alveoli during pregnancy.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Genetics and Physiology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA. mammary@nih.gov

ABSTRACT
Functional development of mammary epithelium during pregnancy depends on prolactin signaling. However, the underlying molecular and cellular events are not fully understood. We examined the specific contributions of the prolactin receptor (PrlR) and the signal transducers and activators of transcription 5a and 5b (referred to as Stat5) in the formation and differentiation of mammary alveolar epithelium. PrlR- and Stat5- mammary epithelia were transplanted into wild-type hosts, and pregnancy-mediated development was investigated at a histological and molecular level. Stat5- mammary epithelium developed ducts but failed to form alveoli, and no milk protein gene expression was observed. In contrast, PrlR- epithelium formed alveoli-like structures with small open lumina. Electron microscopy revealed undifferentiated features of organelles and a perturbation of cell-cell contacts in PrlR- and Stat5- epithelia. Expression of NKCC1, an Na-K-Cl cotransporter characteristic for ductal epithelia, and ZO-1, a protein associated with tight junction, were maintained in the alveoli-like structures of PrlR- and Stat5- epithelia. In contrast, the Na-Pi cotransporter Npt2b, and the gap junction component connexin 32, usually expressed in secretory epithelia, were undetectable in PrlR- and Stat5- mice. These data demonstrate that signaling via the PrlR and Stat5 is critical for the proliferation and differentiation of mammary alveoli during pregnancy.

Show MeSH