RESUMO
Lymphatic vessels arise chiefly from preexisting embryonic veins. Genetic regulators of lymphatic fate are known, but how dynamic cellular changes contribute during the acquisition of lymphatic identity is not understood. We report the visualization of zebrafish lymphatic precursor cell dynamics during fate restriction. In the cardinal vein, cellular commitment is linked with the division of bipotential Prox1-positive precursor cells, which occurs immediately prior to sprouting angiogenesis. Following precursor division, identities are established asymmetrically in daughter cells; one daughter cell becomes lymphatic and progressively upregulates Prox1, and the other downregulates Prox1 and remains in the vein. Vegfc drives cell division and Prox1 expression in lymphatic daughter cells, coupling signaling dynamics with daughter cell fate restriction and precursor division.
Assuntos
Proteínas de Homeodomínio/metabolismo , Vasos Linfáticos/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Fator C de Crescimento do Endotélio Vascular/metabolismo , Peixe-Zebra/metabolismo , Animais , Animais Geneticamente Modificados , Divisão Celular , Embrião não Mamífero/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Genes Reporter , Proteínas de Homeodomínio/genética , Linfangiogênese/fisiologia , Vasos Linfáticos/citologia , Microscopia Confocal , Neovascularização Fisiológica , Transdução de Sinais , Proteínas Supressoras de Tumor/genética , Fator C de Crescimento do Endotélio Vascular/genética , Peixe-Zebra/crescimento & desenvolvimentoRESUMO
In mammals, the homeodomain transcription factor Prox1 acts as the central regulator of lymphatic cell fate. Its restricted expression in a subset of cardinal vein cells leads to a switch towards lymphatic specification and hence represents a prerequisite for the initiation of lymphangiogenesis. Murine Prox1-null embryos lack lymphatic structures, and sustained expression of Prox1 is indispensable for the maintenance of lymphatic cell fate even at adult stages, highlighting the unique importance of this gene for the lymphatic lineage. Whether this pre-eminent role of Prox1 within the lymphatic vasculature is conserved in other vertebrate classes has remained unresolved, mainly owing to the lack of availability of loss-of-function mutants. Here, we re-examine the role of Prox1a in zebrafish lymphangiogenesis. First, using a transgenic reporter line, we show that prox1a is initially expressed in different endothelial compartments, becoming restricted to lymphatic endothelial cells only at later stages. Second, using targeted mutagenesis, we show that Prox1a is dispensable for lymphatic specification and subsequent lymphangiogenesis in zebrafish. In line with this result, we found that the functionally related transcription factors Coup-TFII and Sox18 are also dispensable for lymphangiogenesis. Together, these findings suggest that lymphatic commitment in zebrafish and mice is controlled in fundamentally different ways.
Assuntos
Proteínas de Homeodomínio/fisiologia , Linfangiogênese/fisiologia , Proteínas Supressoras de Tumor/fisiologia , Proteínas de Peixe-Zebra/fisiologia , Peixe-Zebra/crescimento & desenvolvimento , Animais , Animais Geneticamente Modificados , Fator II de Transcrição COUP/deficiência , Fator II de Transcrição COUP/genética , Fator II de Transcrição COUP/metabolismo , Diferenciação Celular , Linhagem da Célula , Células Endoteliais/citologia , Células Endoteliais/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Homeodomínio/genética , Linfangiogênese/genética , Vasos Linfáticos/citologia , Vasos Linfáticos/metabolismo , Camundongos , Camundongos Knockout , Mutação , Fatores de Transcrição SOXF/deficiência , Fatores de Transcrição SOXF/genética , Fatores de Transcrição SOXF/metabolismo , Especificidade da Espécie , Proteínas Supressoras de Tumor/deficiência , Proteínas Supressoras de Tumor/genética , Peixe-Zebra/genética , Peixe-Zebra/fisiologia , Proteínas de Peixe-Zebra/deficiência , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismoRESUMO
RATIONALE: The emergence of lymphatic endothelial cells (LECs) seems to be highly regulated during development. Although several factors that promote the differentiation of LECs in embryonic development have been identified, those that negatively regulate this process are largely unknown. OBJECTIVE: Our aim was to delineate the role of bone morphogenetic protein (BMP) 2 signaling in lymphatic development. METHODS AND RESULTS: BMP2 signaling negatively regulates the formation of LECs. Developing LECs lack any detectable BMP signaling activity in both zebrafish and mouse embryos, and excess BMP2 signaling in zebrafish embryos and mouse embryonic stem cell-derived embryoid bodies substantially decrease the emergence of LECs. Mechanistically, BMP2 signaling induces expression of miR-31 and miR-181a in a SMAD-dependent mechanism, which in turn results in attenuated expression of prospero homeobox protein 1 during development. CONCLUSIONS: Our data identify BMP2 as a key negative regulator for the emergence of the lymphatic lineage during vertebrate development.