Shh expression is required for embryonic hair follicle but not mammary gland development.

The embryonic mammary gland and hair follicle are both derived from the ventral ectoderm, and their development depends on a number of common fundamental developmental pathways. While the Hedgehog (Hh) signaling pathway is required for hair follicle morphogenesis, the role of this pathway during embryonic mammary gland development remains undetermined. We demonstrate here that, unlike the hair follicle, both Shh and Ihh are expressed in the developing embryonic mouse mammary rudiment as early as E12.5. In Shh(-/-) embryos, hair follicle development becomes arrested at an early stage, while the mammary rudiment, which continues to express Ihh, develops in a manner indistinguishable from that of wild-type littermates. The five pairs of mammary buds in Shh(-/-) female embryos exhibit normal branching morphogenesis at E16.5, forming a rudimentary ductal structure identical to wild-type embryonic mammary glands. We further demonstrate that loss of Hh signaling causes altered cyclin D1 expression in the embryonic dermal mesenchyme. Specifically, cyclin D1 is expressed at E14.5 principally in the condensed mesenchymal cells of the presumptive hair follicles and in both mesenchymal and epithelial cells of the mammary rudiments in wild-type and Shh-deficient embryos. By E18.5, robust cyclin D1 expression is maintained in mammary rudiments of both wild-type and Shh-deficient embryos. In hair follicles of wild-type embryos by E18.5, cyclin D1 expression switches to follicular epithelial cells. In contrast, strong cyclin D1 expression is observed principally in the mesenchymal cells of arrested hair follicles in Shh(-/-) embryos at E18.5. These data reveal that, despite the common embryonic origin of hair follicles and mammary glands, distinct patterns of Hh-family expression occur in these two tissues. Furthermore, these data suggest that cyclin D1 expression in the embryonic hair follicle is mediated by both Hh-independent and Hh-dependent mechanisms.

[1]  K. Matsumoto,et al.  Emerging multipotent aspects of hepatocyte growth factor. , 1996, Journal of biochemistry.

[2]  M. Scott,et al.  Conservation of the hedgehog/patched signaling pathway from flies to mice: induction of a mouse patched gene by Hedgehog. , 1996, Genes & development.

[3]  P. Beachy,et al.  Cyclopia and defective axial patterning in mice lacking Sonic hedgehog gene function , 1996, Nature.

[4]  A. McMahon,et al.  Hedgehog and Bmp genes are coexpressed at many diverse sites of cell-cell interaction in the mouse embryo. , 1995, Developmental biology.

[5]  A. McMahon,et al.  Genetic manipulation of hedgehog signaling in the endochondral skeleton reveals a direct role in the regulation of chondrocyte proliferation. , 2001, Development.

[6]  C. Birchmeier,et al.  Developmental roles of HGF/SF and its receptor, the c-Met tyrosine kinase. , 1998, Trends in cell biology.

[7]  N. Copeland,et al.  Cloning, expression, and chromosomal location of SHH and IHH: two human homologues of the Drosophila segment polarity gene hedgehog. , 1995, Genomics.

[8]  C. Albanese,et al.  The cyclin D1 gene is a target of the beta-catenin/LEF-1 pathway. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[9]  E. Fuchs,et al.  De Novo Hair Follicle Morphogenesis and Hair Tumors in Mice Expressing a Truncated β-Catenin in Skin , 1998, Cell.

[10]  J. Wysolmerski,et al.  Overexpression of parathyroid hormone-related protein or parathyroid hormone in transgenic mice impairs branching morphogenesis during mammary gland development. , 1995, Development.

[11]  W Gaffield,et al.  Essential role for Sonic hedgehog during hair follicle morphogenesis. , 1999, Developmental biology.

[12]  R. Maas,et al.  Msx2 deficiency in mice causes pleiotropic defects in bone growth and ectodermal organ formation , 2000, Nature Genetics.

[13]  J. Rossant,et al.  Diminished Sonic hedgehog signaling and lack of floor plate differentiation in Gli2 mutant mice. , 1998, Development.

[14]  R. Cardiff,et al.  Activation of different Wnt/β-catenin signaling components in mammary epithelium induces transdifferentiation and the formation of pilar tumors , 2002, Oncogene.

[15]  A. McMahon,et al.  The whereabouts of a morphogen: direct evidence for short- and graded long-range activity of hedgehog signaling peptides. , 2001, Developmental biology.

[16]  S. Elledge,et al.  Cyclin D1 provides a link between development and oncogenesis in the retina and breast , 1995, Cell.

[17]  D. Rowitch,et al.  Sonic hedgehog Promotes G1 Cyclin Expression and Sustained Cell Cycle Progression in Mammalian Neuronal Precursors , 2000, Molecular and Cellular Biology.

[18]  L. Hennighausen,et al.  Differential requirements for shh in mammary tissue and hair follicle morphogenesis. , 2002, Developmental biology.

[19]  J. Heath.  Morphogenesis of the mammary gland , 1977, Nature.

[20]  S. Millar,et al.  WNT signals are required for the initiation of hair follicle development. , 2002, Developmental cell.

[21]  L. Hennighausen,et al.  Think globally, act locally: the making of a mouse mammary gland. , 1998, Genes & development.

[22]  C. Tickle,et al.  Expression of ptc and gli genes in talpid3 suggests bifurcation in Shh pathway. , 1999, Development.

[23]  A. Vaahtokari,et al.  Regulation of organogenesis. Common molecular mechanisms regulating the development of teeth and other organs. , 1995, The International journal of developmental biology.

[24]  L. Hennighausen,et al.  Developing a Mammary Gland is a Stāt Affair , 2004, Journal of Mammary Gland Biology and Neoplasia.

[25]  J. Thiery,et al.  Role of FGF10/FGFR2b signaling during mammary gland development in the mouse embryo. , 2002, Development.

[26]  A. McMahon,et al.  Indian hedgehog signaling regulates proliferation and differentiation of chondrocytes and is essential for bone formation. , 1999, Genes & development.

[27]  T. Nguyen,et al.  Spatial and temporal distribution of Indian hedgehog mRNA in the embryonic mouse mandible. , 1996, Archives of oral biology.

[28]  B. Larson.  Milk: The Mammary Gland and Its Secretions , 1961 .

[29]  L. Wolpert.  Developmental Biology , 1968, Nature.

[30]  C. Sugnet,et al.  The Gli2 transcription factor is required for normal mouse mammary gland development. , 2001, Developmental biology.

[31]  C. Hui,et al.  Sonic hedgehog-dependent activation of Gli2 is essential for embryonic hair follicle development. , 2003, Genes & development.

[32]  Klaus Kratochwil,et al.  Regulation of Mammary Gland Development by Tissue Interaction , 2004, Journal of Mammary Gland Biology and Neoplasia.

[33]  A. Brivanlou,et al.  Neural patterning in the vertebrate embryo. , 2001, International review of cytology.

[34]  Wei Du,et al.  Hedgehog regulates cell growth and proliferation by inducing Cyclin D and Cyclin E , 2002, Nature.

[35]  S. Noji,et al.  Early chick limb cartilaginous elements possess polarizing activity and express hedgehog‐related morphogenetic factors , 1996, Developmental dynamics : an official publication of the American Association of Anatomists.

[36]  Takashi Takabatake,et al.  Ptch2, a second mouse Patched gene is co-expressed with Sonic hedgehog , 1998, Nature Genetics.

[37]  H. Heng,et al.  Specific and redundant functions of Gli2 and Gli3 zinc finger genes in skeletal patterning and development. , 1997, Development.

[38]  I Fariñas,et al.  Development of several organs that require inductive epithelial-mesenchymal interactions is impaired in LEF-1-deficient mice. , 1994, Genes & development.

[39]  R. Paus,et al.  Sonic hedgehog signaling is essential for hair development , 1998, Current Biology.

[40]  L. Hennighausen,et al.  Side-branching in the mammary gland: the progesterone-Wnt connection. , 2000, Genes & development.

[41]  P. Hamel,et al.  Alx‐4, a transcriptional activator whose expression is restricted to sites of epithelial–mesenchymal interactions , 1998, Developmental dynamics : an official publication of the American Association of Anatomists.

[42]  C. Tabin,et al.  Biochemical evidence that Patched is the Hedgehog receptor , 1996, Nature.

[43]  C. Sugnet,et al.  Defects in mouse mammary gland development caused by conditional haploinsufficiency of Patched-1. , 1999, Development.

[44]  M. Nakafuku,et al.  Regulation of Gli2 and Gli3 activities by an amino-terminal repression domain: implication of Gli2 and Gli3 as primary mediators of Shh signaling. , 1999, Development.

[45]  L. Hennighausen,et al.  Signaling pathways in mammary gland development. , 2001, Developmental cell.

[46]  M. Bissell,et al.  The influence of tissue microenvironment (stroma and extracellular matrix) on the development and function of mammary epithelium. , 1993, Epithelial cell biology.

[47]  E. Fuchs,et al.  Overexpression of parathyroid hormone-related protein in the skin of transgenic mice interferes with hair follicle development. , 1994, Proceedings of the National Academy of Sciences of the United States of America.

[48]  L. Hennighausen,et al.  Prolactin Signaling in Mammary Gland Development* , 1997, The Journal of Biological Chemistry.

[49]  F. Sauvage,et al.  Sonic hedgehog signaling by the Patched–Smoothened receptor complex , 1999, Current Biology.

[50]  B. Morgan,et al.  Stage-specific effects of sonic hedgehog expression in the epidermis. , 1998, Developmental biology.

[51]  S. Scherer,et al.  Mutations in the human Sonic Hedgehog gene cause holoprosencephaly , 1996, Nature Genetics.

[52]  A. G. Kefalas,et al.  Think globally, act locally , 1998 .