Ras-dva, a member of novel family of small GTPases, is required for the anterior ectoderm patterning in theXenopus laevisembryo

Abstract

Ras-like small GTPases are involved in the regulation of many processes essential for the specification of the vertebrate body plan. Recently, we identified the gene of novel small GTPase Ras-dva, which is specifically expressed at the anterior margin of the neural plate of the Xenopus laevis embryo. Now, we demonstrate that Ras-dva and its homologs in other species constitute a novel protein family, distinct from the previously known families of small GTPases. We show that the expression of Ras-dvabegins during gastrulation throughout the anterior ectoderm and is activated by the homeodomain transcription factor Otx2; however, later on, Ras-dva expression is inhibited in the anterior neural plate by another homeodomain factor Xanf1. Downregulation of Ras-dva functioning by the dominant-negative mutant or by the antisense morpholino oligonucleotides results in severe malformations of the forebrain and derivatives of the cranial placodes. Importantly, although the observed abnormalities can be rescued by co-injection of the Ras-dva mRNA, they cannot be rescued by the mRNA of the closest Ras-dva homolog from another family of small GTPases, Ras. This fact indicates functional specificity of the Ras-dva signaling pathway. At the molecular level, downregulation of Ras-dva inhibits the expression of several regulators of the anterior neural plate and folds patterning, such as Otx2, BF-1 (also known as Foxg1), Xag2, Pax6, Slug and Sox9, and interferes with FGF8 signaling within the anterior ectoderm. By contrast, expression of the epidermal regulator BMP4 and its target genes, Vent1, Vent2band Msx1, is upregulated. Together, the data obtained indicate that Ras-dva is an essential component of the signaling network that patterns the early anterior neural plate and the adjacent ectoderm in the Xenopus laevis embryos.

Zoledronate, ibandronate and clodronate enhance osteoblast differentiation in a dose dependent manner – A quantitative in vitro gene expression analysis of Dlx5, Runx2, OCN, MSX1 and MSX2

“…These signalling molecules control regulator proteins, also responsible for bone differentiation, such as Smad or MSX1. Tereshina et al, found an elevated gene expression of MSX1 due to small GTPase activation (Tereshina et al, 2006). This GTPase interaction causes inappropriate and sustained stimulation rather than inhibition, similar to bisphosphonate associated posttranslational protein modification.…”

“…Mutations in these genes might result in hypodontia, various kinds of craniosynostosis, facial anomalies, or parietal foramina in the head and neck regions (Cohen, 2006). MSX1, regulated by small GTPase, such as Ras-dva (Tereshina et al, 2006), as well as MSX2 are both enhanced by high concentrations (5 Â 10 À5 M) of nitrogen-containing bisphosphonates. In contrast to lower concentrations (5 Â 10 À6 and 5 Â 10 À7 ), Ibandronate and zoledronate stimulation caused a strong gene expression enhancement of MSX1 and MSX2 after 10 days.…”

Ras-dva1 small GTPase regulates telencephalon development in Xenopus laevis embryos by controlling Fgf8 and Agr signaling at the anterior border of the neural plate

“…All plasmids were described previously (Ermakova et al, 1999; Ermakova et al, 2007; Ivanova et al, 2013; Novoselov et al, 2003; Tereshina et al, 2006). Synthetic capped mRNA and anti-sense RNA dig-labeled probes for in situ hybridization were prepared by using mMessage Machine Kits (Ambion).…”

“…Recently, we have shown that in the Xenopus laevis embryo, the small GTPase Ras-dva1, which is expressed near ANB, is necessary for the Fgf8-mediated expression of the telencephalic regulator FoxG1 (previously named BF1 ) in cells at the anterior margin of the neural plate (Tereshina et al, 2006). This expression pattern indicates that Ras-dva1, which is a membrane-bound GTPase (Tereshina et al, 2007), might control the propagation of Fgf8 signal within these cells, composing the telencephalic rudiment.…”

Characterization of anIn VitroDifferentiation Assay for Pancreatic-Like Cell Development from Murine Embryonic Stem Cells: Detailed Gene Expression Analysis

“…Markers for the three germ layers and lineage-specific progenitors were then examined. The ectoderm marker, Pax6, 40 was expressed as early as 2 h (not shown) and until day 4 (Fig. 1C, D).…”