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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.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.

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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NKCC1 and smooth muscle actin are expressed in PrlR- and Stat5- alveoli-like structures at parturition, but not in wild-type mice. Immunohistochemical staining of NKCC1 (red) and smooth muscle actin (green) in mammary epithelia of virgin mice (A, C, and E) and after parturition (B, D, and F). NKCC1 levels were high in ductal epithelium of wild-type virgin mice (A) and sharply reduced in alveoli by pregnancy day 12 (G, circle) and at parturition (B). PrlR- and Stat5- epithelia maintained high levels of NKCC1 at parturition (D and F, compare white arrows with white arrow in G).
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fig6: NKCC1 and smooth muscle actin are expressed in PrlR- and Stat5- alveoli-like structures at parturition, but not in wild-type mice. Immunohistochemical staining of NKCC1 (red) and smooth muscle actin (green) in mammary epithelia of virgin mice (A, C, and E) and after parturition (B, D, and F). NKCC1 levels were high in ductal epithelium of wild-type virgin mice (A) and sharply reduced in alveoli by pregnancy day 12 (G, circle) and at parturition (B). PrlR- and Stat5- epithelia maintained high levels of NKCC1 at parturition (D and F, compare white arrows with white arrow in G).

Mentions: Whole mount and histological analyses have demonstrated that the formation of mammary alveolar epithelium was severely impaired in the absence of the PrlR or Stat5. However, these types of analyses do not allow the identification of the epithelial cells as ductal or alveolar. To further determine the histological identity of these cells, we investigated the expression of proteins that characterize either ductal or secretory alveolar epithelium. We have observed that the Na-K-Cl cotransporter (NKCCl) is expressed at high levels in virgin mice and is located on the basolateral membrane of ductal epithelial cells, and unpublished data). Further, NKCC1 expression levels decreased in developing alveoli but are maintained in some cells of the ductal epithelia during pregnancy. Therefore, we examined the expression of NKCC1 by immunohistochemistry in transplanted PrlR- and Stat5- epithelia in virgin mice and at parturition. In virgin mice, NKCC1 was detected in endogenous epithelium and PrlR- and Stat5- transplants (Fig. 6, A, C, and E). At parturition, the levels of NKCC1 were sharply reduced in wild-type secretory alveolar cells (Fig. 6 B). In contrast, NKCC1 expression was consistently higher in PrlR- and Stat5- epithelia at parturition (Fig. 6, D and F), and the alveoli-like structures stained strongly for NKCC1. At pregnant day 12, wild-type alveolar cells already had reduced NKCC1 levels (Fig. 6 G). These results suggest that the cells forming alveoli-like structures still maintain features of ductal epithelia. Smooth muscle actin, which characterizes myoepithelial cells, was found in PrlR- and Stat5-, and control epithelia from virgin mice (Fig. 6, A, C, and E). At parturition, smooth muscle actin staining demonstrated a contiguous layer of thin myoepithelial cells surrounding the fully expanded wild-type alveoli (Fig. 6 B). On the other hand, PrlR- and Stat5- (Fig. 6, D and F) epithelia exhibited a staining pattern very similar to that seen in virgin wild-type epithelium (Fig. 6 A). The expression pattern of smooth muscle actin in alveoli-like structures was identical to that observed in ducts (Fig. 6, A, E, and F).


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)

NKCC1 and smooth muscle actin are expressed in PrlR- and Stat5- alveoli-like structures at parturition, but not in wild-type mice. Immunohistochemical staining of NKCC1 (red) and smooth muscle actin (green) in mammary epithelia of virgin mice (A, C, and E) and after parturition (B, D, and F). NKCC1 levels were high in ductal epithelium of wild-type virgin mice (A) and sharply reduced in alveoli by pregnancy day 12 (G, circle) and at parturition (B). PrlR- and Stat5- epithelia maintained high levels of NKCC1 at parturition (D and F, compare white arrows with white arrow in G).
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Related In: Results  -  Collection

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fig6: NKCC1 and smooth muscle actin are expressed in PrlR- and Stat5- alveoli-like structures at parturition, but not in wild-type mice. Immunohistochemical staining of NKCC1 (red) and smooth muscle actin (green) in mammary epithelia of virgin mice (A, C, and E) and after parturition (B, D, and F). NKCC1 levels were high in ductal epithelium of wild-type virgin mice (A) and sharply reduced in alveoli by pregnancy day 12 (G, circle) and at parturition (B). PrlR- and Stat5- epithelia maintained high levels of NKCC1 at parturition (D and F, compare white arrows with white arrow in G).
Mentions: Whole mount and histological analyses have demonstrated that the formation of mammary alveolar epithelium was severely impaired in the absence of the PrlR or Stat5. However, these types of analyses do not allow the identification of the epithelial cells as ductal or alveolar. To further determine the histological identity of these cells, we investigated the expression of proteins that characterize either ductal or secretory alveolar epithelium. We have observed that the Na-K-Cl cotransporter (NKCCl) is expressed at high levels in virgin mice and is located on the basolateral membrane of ductal epithelial cells, and unpublished data). Further, NKCC1 expression levels decreased in developing alveoli but are maintained in some cells of the ductal epithelia during pregnancy. Therefore, we examined the expression of NKCC1 by immunohistochemistry in transplanted PrlR- and Stat5- epithelia in virgin mice and at parturition. In virgin mice, NKCC1 was detected in endogenous epithelium and PrlR- and Stat5- transplants (Fig. 6, A, C, and E). At parturition, the levels of NKCC1 were sharply reduced in wild-type secretory alveolar cells (Fig. 6 B). In contrast, NKCC1 expression was consistently higher in PrlR- and Stat5- epithelia at parturition (Fig. 6, D and F), and the alveoli-like structures stained strongly for NKCC1. At pregnant day 12, wild-type alveolar cells already had reduced NKCC1 levels (Fig. 6 G). These results suggest that the cells forming alveoli-like structures still maintain features of ductal epithelia. Smooth muscle actin, which characterizes myoepithelial cells, was found in PrlR- and Stat5-, and control epithelia from virgin mice (Fig. 6, A, C, and E). At parturition, smooth muscle actin staining demonstrated a contiguous layer of thin myoepithelial cells surrounding the fully expanded wild-type alveoli (Fig. 6 B). On the other hand, PrlR- and Stat5- (Fig. 6, D and F) epithelia exhibited a staining pattern very similar to that seen in virgin wild-type epithelium (Fig. 6 A). The expression pattern of smooth muscle actin in alveoli-like structures was identical to that observed in ducts (Fig. 6, A, E, and F).

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.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.

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
Related in: MedlinePlus