RESUMO
Sirenomelia or mermaid-like phenotype is one of the principal human congenital malformations that can be traced back to the stage of gastrulation. Sirenomelia is characterized by the fusion of the two hindlimbs into a single one. In the mouse, sirens have been observed in crosses between specific strains and as the consequence of mutations that increase retinoic acid levels. We report that the loss of bone morphogenetic protein 7 (Bmp7) in combination with a half dose or complete loss of twisted gastrulation (Tsg) causes sirenomelia in the mouse. Tsg is a Bmp- and chordin-binding protein that has multiple effects on Bmp metabolism in the extracellular space; Bmp7 is one of many Bmps and is shown here to bind to Tsg. In Xenopus, co-injection of Tsg and Bmp7 morpholino oligonucleotides (MO) has a synergistic effect, greatly inhibiting formation of ventral mesoderm and ventral fin tissue. In the mouse, molecular marker studies indicate that the sirenomelia phenotype is associated with a defect in the formation of ventroposterior mesoderm. These experiments demonstrate that dorsoventral patterning of the mouse posterior mesoderm is regulated by Bmp signaling, as is the case in other vertebrates. Sirens result from a fusion of the hindlimb buds caused by a defect in the formation of ventral mesoderm.
Assuntos
Proteínas Morfogenéticas Ósseas/genética , Ectromelia/veterinária , Mesoderma/fisiologia , Camundongos , Proteínas/genética , Doenças dos Roedores/embriologia , Transdução de Sinais , Fator de Crescimento Transformador beta/genética , Animais , Western Blotting/veterinária , Padronização Corporal/fisiologia , Proteína Morfogenética Óssea 7 , Proteínas Morfogenéticas Ósseas/metabolismo , Ectromelia/embriologia , Ectromelia/genética , Regulação da Expressão Gênica no Desenvolvimento , Membro Posterior/patologia , Técnicas Histológicas/veterinária , Hibridização In Situ/veterinária , Mutação/genética , Oligonucleotídeos Antissenso , Proteínas/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa/veterinária , Doenças dos Roedores/genética , Fator de Crescimento Transformador beta/metabolismo , Xenopus , Proteínas de XenopusRESUMO
Convergent extension movements occur ubiquitously in animal development. This special type of cell movement is controlled by the Wnt/planar cell polarity (PCP) pathway. Here we show that Xenopus paraxial protocadherin (XPAPC) functionally interacts with the Wnt/PCP pathway in the control of convergence and extension (CE) movements in Xenopus laevis. XPAPC functions as a signalling molecule that coordinates cell polarity of the involuting mesoderm in mediolateral orientation and thus selectively promotes convergence in CE movements. XPAPC signals through the small GTPases Rho A and Rac 1 and c-jun N-terminal kinase (JNK). Loss of XPAPC function blocks Rho A-mediated JNK activation. Despite common downstream components, XPAPC and Wnt/PCP signalling are not redundant, and the activity of both, XPAPC and PCP signalling, is required to coordinate CE movements.
Assuntos
Caderinas/metabolismo , Polaridade Celular , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Xenopus laevis/embriologia , Xenopus laevis/metabolismo , Proteína rhoA de Ligação ao GTP/metabolismo , Animais , Caderinas/genética , Embrião não Mamífero/embriologia , Embrião não Mamífero/metabolismo , Ativação Enzimática , Gástrula/citologia , Gástrula/metabolismo , Hibridização In Situ , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Proteínas Quinases JNK Ativadas por Mitógeno/genética , Protocaderinas , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Transdução de Sinais , Proteínas Wnt , Proteínas de Xenopus , Xenopus laevis/genética , Proteínas rac1 de Ligação ao GTP/metabolismo , Proteína rhoA de Ligação ao GTP/genéticaRESUMO
Dorsoventral patterning in animal development is regulated by a morphogenetic gradient of Bone morphogenetic protein signalling, which is established by a set of proteins that are conserved from Drosophila to vertebrates. These include Chordin (Chd)/Short gastrulation, Xolloid/Tolloid and Twisted gastrulation. Here, we report the identification of a cell-surface component of this morphogenetic pathway. Prompted by the observation that Chd protein bound to the surface of certain cell lines with subnanomolar affinity, we identified two cell-surface proteins that bind to Chd, one of which corresponds to Integrin-alpha3. Integrin-alpha3 and Chd are co-expressed in the Xenopus embryo. Transfection of Integrin-alpha3 increased the binding of Chd to the cell surface, which was competed by an excess of soluble Integrin-alpha3. After binding to the cell surface, Chd was translocated into intracellular endocytic compartments in a temperature-dependent manner. We propose that Integrin-alpha3 may regulate the concentration of Chd protein in the extracellular space by endocytosis.
Assuntos
Membrana Celular/metabolismo , Endocitose , Glicoproteínas/metabolismo , Integrina alfa3/metabolismo , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Animais , Células COS , Linhagem Celular , Drosophila , Ligação ProteicaRESUMO
How do very diverse signaling pathways induce neural differentiation in Xenopus? Anti-BMP (Chordin), FGF8, and IGF2 signals are integrated in the embryo via the regulation of Smad1 phosphorylation. Neural induction results from the combined inhibition of BMP receptor serine/threonine kinases and activation of receptor tyrosine kinases that signal through MAPK and phosphorylate Smad1 in the linker region, further inhibiting Smad1 transcriptional activity. This hard-wired molecular mechanism at the level of the Smad1 transcription factor may help explain the opposing activities of IGF, FGF, and BMP signals not only in neural induction, but also in other aspects of vertebrate development.