RESUMO
Ephrins and their tyrosine kinase receptors (Ephs) are a highly conserved family of signaling proteins with various functions during embryonic development. Among others, Eph/ephrin signaling is involved in regulating axon guidance, cell migration, and tissue border formation through inducing modifications of the actin cytoskeleton and cell adhesion. During development ephrins and Ephs are expressed in spatially and temporarily regulated patterns in a wide range of tissues. Here, we analyzed the expression of seven members of the Eph and four member of the ephrin family during early stages of mouse inner ear development by whole-mount in situ hybridization. We detected expressions of EphA2, EphA4, EphA7, EphB1, ephrinA4, and ephrinA5 in and around the forming otic placode between embryonic day (E) 8.5 and E10, and report their detailed expression patterns. Our results reveal dynamic expression of several members of the ephrin/Eph family consistent with functions in otic placode development, invagination and neuroblast delamination.
Assuntos
Orelha Interna/embriologia , Efrinas/genética , Receptores da Família Eph/genética , Animais , Orelha Interna/metabolismo , Ectoderma/embriologia , Ectoderma/metabolismo , Efrinas/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Camundongos , Modelos Biológicos , Organogênese/genética , Organogênese/fisiologia , Receptor EphB1/genética , Receptor EphB1/metabolismo , Receptores da Família Eph/metabolismo , Somitos/embriologia , Somitos/metabolismo , Fatores de TempoRESUMO
Wnt factors are involved in the regulation of all steps of cartilage development. The activity of Wnt factors is generally regulated at the extracellular level by factors like the Dkk family, sFRPs, Cerberus and Wnt inhibitory factor 1 (Wif-1). Here we report that Wif-1 is highly expressed at cartilage-mesenchyme interfaces of the early developing skeleton. In fetal and postnatal skeletal development, Wif-1 is expressed in a sharply restricted zone in the upper hyaline layer of epiphyseal and articular cartilage and in trabecular bone. Coimmunoprecipitation and pull-down assays using recombinant Wif-1 and Wnt factors show specific binding of Wif-1 to Wnt3a, Wnt4, Wnt5a, Wnt7a, Wnt9a and Wnt11. Moreover, Wif-1 was able to block Wnt3a-mediated activation of the canonical Wnt signalling pathway. Consequently, Wif-1 impaired growth of mesenchymal precursor cells and neutralised Wnt3a-mediated inhibition of chondrogenesis in micromass cultures of embryonic chick limb-bud cells. These results identify Wif-1 as a novel extracellular Wnt modulator in cartilage biology.
Assuntos
Cartilagem/embriologia , Cartilagem/metabolismo , Condrogênese , Proteínas da Matriz Extracelular/metabolismo , Mesoderma/embriologia , Mesoderma/metabolismo , Proteínas Wnt/metabolismo , Proteínas Adaptadoras de Transdução de Sinal , Animais , Animais Recém-Nascidos , Proliferação de Células , Embrião de Galinha , Condrogênese/genética , Desenvolvimento Embrionário , Epífises/embriologia , Epífises/metabolismo , Proteínas da Matriz Extracelular/genética , Extremidades/embriologia , Regulação da Expressão Gênica no Desenvolvimento , Peptídeos e Proteínas de Sinalização Intercelular/genética , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Botões de Extremidades/citologia , Botões de Extremidades/embriologia , Botões de Extremidades/metabolismo , Células-Tronco Mesenquimais/citologia , Células-Tronco Mesenquimais/metabolismo , Mesoderma/citologia , Camundongos , Ligação Proteica , Transdução de Sinais , Técnicas de Cultura de Tecidos , Proteína Wnt3 , Proteína Wnt3ARESUMO
A central challenge in embryonic development is to understand how growth and pattern are coordinated to direct emerging new territories during morphogenesis. Here, we report on a signaling cascade that links cell proliferation and fate, promoting formation of a distinct progenitor domain within the developing chick hypothalamus. We show that the downregulation of Shh in floor plate-like cells in the forebrain governs their progression to a distinctive, proliferating hypothalamic progenitor domain. Shh downregulation occurs via a local BMP-Tbx2 pathway, Tbx2 acting to repress Shh expression. We show in vivo and in vitro that forced maintenance of Shh in hypothalamic progenitors prevents their normal morphogenesis, leading to maintenance of the Shh receptor, ptc, and preventing progression to an Emx2(+)-proliferative progenitor state. Our data identify a molecular pathway for the downregulation of Shh via a BMP-Tbx2 pathway and provide a mechanism for expansion of a discrete progenitor domain within the developing forebrain.