Induction and early development of the hematopoietic and immune systems in Xenopus

Turpen, James B.

doi:10.1016/s0145-305x(98)00004-4

Cited by 30 publications

(20 citation statements)

References 62 publications

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“…Although we focused our study on the role of Wnt4 in the development of the VBI, we noticed that Wnt4 is also expressed in the dorsal lateral plate mesoderm (DLPM) and that Wnt4 depletion in the presumptive DLPM abolished the expression of SCL and LMO2. The DLPM is the common precursor of the pronephric duct and the dorsal lateral plate (DLP), which is the source of the first definitive blood cells that colonize the tadpole liver (2). Therefore, Wnt4 appears to be important not only for regulating primitive hematopoiesis but also for definitive hematopoiesis in Xenopus embryos.…”

Section: Discussionmentioning

confidence: 99%

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Wnt/β-catenin signaling is involved in the induction and maintenance of primitive hematopoiesis in the vertebrate embryo

Tran

Sekkali

Imschoot

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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The formation of primitive (embryonic) blood in vertebrates is mediated by spatio-temporally restricted signaling between different tissue layers. In Xenopus , in which primitive blood originates in the ventral blood island, this involves the secretion of bone morphogenetic protein (BMP) ligands by the ectoderm that signal to the underlying mesoderm during gastrulation. Using novel transgenic reporter lines, we report that the canonical Wnt/β-catenin pathway is also activated in the blood islands in Xenopus . Furthermore, Wnt-reporter activity was also detected in the blood islands of the mouse yolk sac. By using morpholino-mediated depletion in Xenopus , we identified Wnt4 as the ligand that is expressed in the mesoderm of the ventral blood island and is essential for the expression of hematopoietic and erythroid marker genes. Injection of an inducible Wnt-interfering construct further showed that, during gastrulation, Wnt/β-catenin signaling is required both in the mesoderm and in the overlying ectoderm for the formation of the ventral blood island. Using recombination assays with embryonic explants, we document that ectodermal BMP4 expression is dependent on Wnt4 signals from the mesoderm. Our results thus reveal a unique role for Wnt4-mediated canonical signaling in the formation and maintenance of the ventral blood island in Xenopus .

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Section: Discussionmentioning

confidence: 99%

“…Definitive hematopoietic stem cells (HSCs) in Xenopus arise from the dorsal lateral plate (DLP). In mammals, these HSCs originate in the aorta gonad-mesonephros region and in the mature yolk sac (2,3). Studies using ES cells and novel transplantation protocols have indicated that primitive progenitors can also contribute to definitive hematopoiesis (4,5).…”

mentioning

confidence: 99%

Wnt/β-catenin signaling is involved in the induction and maintenance of primitive hematopoiesis in the vertebrate embryo

Tran

Sekkali

Imschoot

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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“…In the mouse embryo, Myc is expressed in endothelial-like (PECAM-1 + ) cells that line the blood islands of the yolk sac (Baudino et al, 2002), which give rise to both the embryonic vasculature and primitive hematopoietic cells. In Xenopus, the precursors of blood and vasculature arise in an analogous region coined the ventral blood island (Turpen, 1998). To define precisely the spatial and temporal patterns of Xc-Myc expression in Xenopus embryos, we performed whole-mount in situ hybridization (Fig.…”

Section: XCmentioning

confidence: 99%

A Myc-Slug (Snail2)/Twist regulatory circuit directs vascular development

et al. 2008

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Myc-deficient mice fail to develop normal vascular networks and Myc-deficient embryonic stem cells fail to provoke a tumor angiogenic response when injected into immune compromised mice. However, the molecular underpinnings of these defects are poorly understood. To assess whether Myc indeed contributes to embryonic vasculogenesis we evaluated Myc function in Xenopus laevis embryogenesis. Here, we report that Xc-Myc is required for the normal assembly of endothelial cells into patent vessels during both angiogenesis and lymphangiogenesis. Accordingly, the specific knockdown of Xc-Myc provokes massive embryonic edema and hemorrhage. Conversely, Xc-Myc overexpression triggers the formation of ectopic vascular beds in embryos. Myc is required for normal expression of Slug/Snail2and Twist, and either XSlug/Snail2 or XTwist could compensate for defects manifest by Xc-Myc knockdown. Importantly, knockdown of Xc-Myc, XSlug/Snail2 or XTwist within the lateral plate mesoderm, but not the neural crest, provoked embryonic edema and hemorrhage. Collectively, these findings support a model in which Myc, Twist and Slug/Snail2 function in a regulatory circuit within lateral plate mesoderm that directs normal vessel formation in both the vascular and lymphatic systems.

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“…In this group also, HSC responsible for definitive hematopoiesis do not originate in the ventral blood island, a structure homologous to the YS of amniotes, but from a dorsal region that encompasses the pronephros, liver and dorsal aorta (Reviewed in (Turpen, 1998)). However, lymphopoiesis in some species from this group (Xenopus Laevis) seems to depend on a contribution of precursors from both sites (Bechtold et al, 1992).…”

Section: The Test: Ys-chimaerasmentioning

confidence: 99%

Of birds and mice: hematopoietic stem cell development

Godin

Cumano²

2005

Int. J. Dev. Biol.

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For many years it has been assumed that the ontogeny of the mammalian hematopoietic system involves sequential transfers of hematopoietic stem cells (HSCs) generated in the yolk sac blood islands, to successive hematopoietic organs as these become active in the embryo (fetal liver, thymus, spleen and eventually bone marrow). Very little was known about early events related to hematopoiesis that could take place during the 4.5 day gap separating the appearance of the yolk sac blood islands and the stage of a fully active fetal liver. Experiments performed in birds documented that the yolk sac only produce erythro-myeloid precursors that become extinct after the emergence of a second wave of intra-embryonic HSCs from the region neighbouring the dorsal aorta. The experimental approaches undertaken over the last ten years in the murine model, which are reviewed here, led to the conclusion that the rules governing avian hematopoietic development basically apply to higher vertebrates.

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Induction and early development of the hematopoietic and immune systems in Xenopus

Cited by 30 publications

References 62 publications

Wnt/β-catenin signaling is involved in the induction and maintenance of primitive hematopoiesis in the vertebrate embryo

Wnt/β-catenin signaling is involved in the induction and maintenance of primitive hematopoiesis in the vertebrate embryo

A Myc-Slug (Snail2)/Twist regulatory circuit directs vascular development

Of birds and mice: hematopoietic stem cell development

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