title: Ras signaling is essential for skin development.
abstract: Proliferation in the epidermis is a tightly controlled process. During skin development, epidermis formation and hair follicle morphogenesis crucially depend on the regulated balance between proliferation and differentiation. Here we deleted all three Ras loci (H-Ras, N-Ras and K-Ras) from keratinocytes in vitro as well as specifically from the epidermis in mice using a K5Cre strain. Upon Ras elimination, keratinocytes ceased proliferation and entered into senescence without any signs of apoptosis induction. Constitutive activation of the mitogen-activated protein kinase pathway was able to partially rescue the proliferative defects. In mice, Ras signaling was essential for proper development of the epidermis and hair follicles. Deletion of the three Ras loci during epidermis formation in mouse embryos caused a dramatic decrease in proliferation, resulting in a substantially thinner epidermis and delayed appearance of differentiation markers. We could not detect apoptotic or senescent cells in these embryos suggesting that loss of Ras protein expression only leads to severe hypoproliferation. These observations provide genetic evidence for an essential role of Ras proteins in the control of keratinocyte and epidermal proliferation.
authors.affiliation: Molecular Oncology Programme, Centro Nacional de Investigaciones Oncológicas (CNIO), Spanish National Cancer Research Center, Madrid, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Drosten
authors.affiliation: Molecular Oncology Programme, Centro Nacional de Investigaciones Oncológicas (CNIO), Spanish National Cancer Research Center, Madrid, Spain.
authors.forename: C G
authors.initials: CG
authors.lastname: Lechuga
authors.affiliation: Molecular Oncology Programme, Centro Nacional de Investigaciones Oncológicas (CNIO), Spanish National Cancer Research Center, Madrid, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Barbacid
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D049109:Cell Proliferation; D016922:Cellular Senescence / Q000235:genetics; D004817:Epidermis / Q000196:embryology / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D018859:Hair Follicle / Q000196:embryology / Q000378:metabolism; D015603:Keratinocytes / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D020928:Mitogen-Activated Protein Kinases; D015398:Signal Transduction; D012867:Skin / Q000196:embryology / Q000378:metabolism*; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D048049:Extracellular Signal-Regulated MAP Kinases; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins