title: Intraepithelial paracrine Hedgehog signaling induces the expansion of ciliated cells that express diverse progenitor cell markers in the basal epithelium of the mouse mammary gland.
abstract: The Hedgehog signaling pathway regulates embryo patterning and progenitor cell homeostasis in adult tissues, including epidermal appendages. A role for the Hh pathway in mammary biology and breast cancer has also been suggested. The aim of this study was to analyze Hh signaling in the mouse mammary gland through the generation of transgenic mice that express Sonic Hedgehog (Shh) under the control of the mammary-specific WAP promoter (WAP-Shh mice). To identify mammary cells capable of activating the Hh pathway we bred WAP-Shh mice to Ptch1-lacZ knock-in mice, in which the expression of a nuclear-targeted β-galactosidase reporter protein (β-gal) is driven by the endogenous Patched 1 gene regulatory region. After two cycles of induction of transgenic Shh expression, we detected areas of X-gal reactivity. Immunohistochemical analysis showed nuclear β-gal staining in clusters of mammary cells in WAP-Shh/Ptch1-lacZ bitransgenic mice. These were epithelial cells present in a basal location of displastic ducts and alveoli, adjacent to Shh-expressing luminal cells, and overexpressed epithelial basal markers keratin 5, 14 and 17 and transcription factor p63. Absence of smooth muscle actin expression and a cuboidal morphology differentiated Hh-responding cells from flat-shaped mature myoepithelial cells. Groups of cells expressing stem cell markers integrin β3 and keratins 6 and 15 were also detected within Hh-responding areas. In addition, we found that Hh-responding cells in the mammary glands of WAP-Shh/Ptch1-lacZ mice were ciliated and exhibited a low proliferation rate. Our data show the paracrine nature of hedgehog signaling in the epithelial compartment of the mouse mammary gland, where a subset of basal cells that express mammary progenitor cell markers and exhibit primary cilia is expanded in response to secretory epithelium-derived Shh.
authors.affiliation: Laboratory of Mammary Pathology, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Carretera de Majadahonda a Pozuelo Km 2, Majadahonda 28220, Madrid, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: García-Zaragoza
authors.forename: Raquel
authors.initials: R
authors.lastname: Pérez-Tavarez
authors.forename: Alicia
authors.initials: A
authors.lastname: Ballester
authors.forename: Vanesa
authors.initials: V
authors.lastname: Lafarga
authors.forename: Anaïs
authors.initials: A
authors.lastname: Jiménez-Reinoso
authors.forename: Angel
authors.initials: A
authors.lastname: Ramírez
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Murillas
authors.forename: Marta I
authors.initials: MI
authors.lastname: Gallego
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism*; D002923:Cilia / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism*; D005260:Female; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D053547:Keratin-14 / Q000235:genetics / Q000378:metabolism; D053569:Keratin-15; D053555:Keratin-5 / Q000235:genetics / Q000378:metabolism; D007633:Keratins / Q000235:genetics / Q000378:metabolism; D051741:Kruppel-Like Transcription Factors / Q000032:analysis / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D008894:Milk Proteins / Q000235:genetics / Q000378:metabolism; D000072079:Patched Receptors; D000072081:Patched-1 Receptor; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D000075746:Zinc Finger Protein Gli2
chemical_list: D015415:Biomarkers; C000618551:Gli2 protein, mouse; D053823:Hedgehog Proteins; D053547:Keratin-14; D053569:Keratin-15; D053555:Keratin-5; C507446:Krt14 protein, mouse; C492053:Krt15 protein, mouse; C118917:Krt17 protein, mouse; D051741:Kruppel-Like Transcription Factors; D008894:Milk Proteins; D000072079:Patched Receptors; D000072081:Patched-1 Receptor; C000606240:Ptch1 protein, mouse; D011956:Receptors, Cell Surface; C465570:Shh protein, mouse; D000075746:Zinc Finger Protein Gli2; C024471:whey acidic proteins; D007633:Keratins