Two types of non-canonical Wnt pathways have been described that mediate both posterior neural ectodermal and dorsal mesodermal CE the planar cell polarity (PCP) pathway ( Keller,2002 McEwen and Peifer,2000 Peifer and McEwen,2002) and the Wnt/Ca 2+ pathway( Kuhl et al., 2000). This work identifies XNF-ATc3 as a regulator of neural convergent extension in Xenopus and adds to a short list of molecules involved in this process. Consistent with a function in neural convergent extension, we show that XNF-ATc3 is expressed and transcriptionally active within the neural tube. Targeted injections of dominant-negative XNF-ATc3, or dosing over time with the calcineurin inhibitor cyclosporin in neural tube explants or in whole embryos, shows that inhibition of NF-AT signaling blocks neural convergent extension. This specific activity was further teased apart using a variety of temporal and spatial approaches. In the whole embryo, inhibition of NF-AT reveals a more selective function, affecting only convergent extension in the neural ectoderm. This is seen in whole embryos, mesodermal explants and posterior neural explants, solidly implicating a role of NF-AT in convergent extension. In this paper, we show that activation of NF-AT, a transcription factor known to modulate multiple signaling events, inhibits convergent extension in the dorsal mesoderm and in the posterior neural ectoderm. In Xenopus, convergent extension occurs in the dorsal mesoderm and posterior neural ectoderm, and is mediated by similar molecular pathways within these tissues.
Convergent extension is the primary driving force elongating the anteroposterior body axis.
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