Distinct mechanisms control the timing of differentiation of two myeloid populations in Xenopus ventral blood islands

Abstract

Previous study has suggested that distinct populations of myeloid cells exist in the anterior ventral blood islands (aVBI) and posterior ventral blood islands (pVBI) in Xenopus neurula embryo. However, details for differentiation programs of these two populations have not been elucidated. In the present study, we examined the role of Wnt, vascular endothelial growth factor (VEGF) and fibroblast growth factor signals in the regulation of myeloid cell differentiation in the dorsal marginal zone and ventral marginal zone explants that are the sources of myeloid cells in the aVBI and pVBI. We found that regulation of Wnt activity is essential for the differentiation of myeloid cells in the aVBI but is not required for the differentiation of myeloid cells in the pVBI. Endogenous activity of the VEGF signal is necessary for differentiation of myeloid cells in the pVBI but is not involved in the differentiation of myeloid cells in the aVBI. Overall results reveal that distinct mechanisms are involved in the myeloid, erythroid and endothelial cell differentiation in the aVBI and pVBI.

GATA2 regulates Wnt signaling to promote primitive red blood cell fate

“…To do this, the ventral half of embryos, which gives rise to the majority of RBCs in the VBI (Ciau-Uitz et al, 2010; Maeno et al, 2012), was explanted and ectoderm was either retained or removed at successive stages of development, from mid-gastrulation (stage 11) through the end of gastrulation (stage 13). The ventral explants were cultured until wild type siblings reached the tailbud stage (stage 34) and then assayed by whole mount in situ hybridization (WMISH) for expression of globin , a marker of differentiated RBCs (assay illustrated in Fig.…”

Expression and localization of Rdd proteins inXenopusembryo

“…This treatment suppressed the expression of tie-2 , a vascular precursor cell marker (Fig. 5A), at the tailbud stage, and resultant tadpoles had an impaired morphology of vascularization (data not shown) [28]. The tailbud embryos injected with VEGF MO showed loss of Rdd protein localization at the vascular structures, such as vitelline veins, inter-somitic vasculature, and branchial arches (Fig.…”

“…Xenopus laevis embryos were obtained as previously described [28]. Developmental stages were determined as described by Niuewkoop and Faber [32].…”

“…When these embryos reached st. 8, the animal cap was excised and cultured in 50% Marc's Modified Ringer solution (100 mM NaCl, 2 mM CaCl 2 , 1 mM MgCl 2 , 5 mM HEPES, pH 7.4) containing an antibiotic (30 g/ml kanamycin sulfate) until st. 20. MOs used in the study are the same as those used in previous studies: Rdd3/4 MO, 5'-TAAAGA-TGG-TGC-TCA-CTC-TCA-GCA-T-3' [30]; VEGF MO, 5'-TGG-CCT-TTT-AGT-ACT-TGA-AAG-ACG-G-3' [28]. …”

“…It was shown in Xenopus that VEGF produced in the hypochord is essential for formation of the vascular structure in the dorsal-lateral plate [24, 25]. Activation and inactivation of the fibroblast growth factor signal control the fate of vascular and blood cell lineages in the ventral blood island mesoderm [26, 27, 28]. A recent study also demonstrated a role of R-spondings and Wnt signal in activation of vascular cell differentiation [29].…”