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Dev Biol 2009 May 15;3292:327-37. doi: 10.1016/j.ydbio.2009.03.004.
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XsFRP5 modulates endodermal organogenesis in Xenopus laevis.

Damianitsch K , Melchert J , Pieler T .

Canonical Wnt signalling is known to be involved in the regulation of differentiation and proliferation in the context of endodermal organogenesis. Wnt mediated beta-catenin activation is understood to be modulated by secreted Frizzled-related proteins, such as XsFRP5, which is dynamically expressed in the prospective liver/ventral pancreatic precursor cells during late neurula stages, becoming liver specific at tailbud stages and shifting to the posterior stomach/anterior duodenum territory during tadpole stages of Xenopus embryogenesis. These expression characteristics prompted us to analyse the function of XsFRP5 in the context of endodermal organogenesis. We demonstrate that XsFRP5 can form a complex with and inhibit a multitude of different Wnt ligands, including both canonical and non-canonical ones. Knockdown of XsFRP5 results in transient pancreatic hypoplasia as well as in an enlargement of the stomach. In VegT-injected animal cap explants, XsFRP5 can induce expression of exocrine but not endocrine pancreatic marker genes. Both, its expression characteristics as well as its interactions with XsFRP5, define Wnt2b as a putative target for XsFRP5 in vivo. Knockdown of Wnt2b results in a hypoplastic stomach as well as in hypoplasia of the pancreas. On the basis of these findings we propose that XsFRP5 exerts an early regulatory function in the specification of the ventral pancreas, as well as a late function in controlling stomach size via inhibition of Wnt signalling.

PubMed ID: 19285490
Article link: Dev Biol

Species referenced: Xenopus laevis
Genes referenced: fga pdia2 pdx1 ptf1a sfrp5 sox2 vegt wnt11 wnt2b wnt5a
Morpholinos: sfrp5 MO3 sfrp5 MO4 wnt2b MO2 wnt2b MO3 wnt2b MO4

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