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Int J Dev Biol 1998 Sep 01;426:763-74.
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Evidence for non-axial A/P patterning in the nonneural ectoderm of Xenopus and zebrafish pregastrula embryos.

Read EM , Rodaway AR , Neave B , Brandon N , Holder N , Patient RK , Walmsley ME .

Recent studies in early Xenopus and zebrafish embryos have demonstrated that posteriorizing, non-axial signals arising from outside the organizer (or shield) contribute to A/P patterning of the neural axis, in contradiction to the classical Spemann model in which such signals were proposed to be solely organizer derived. Our studies on the early expression of the transcription factors GATA-2 and 3 in both Xenopus and zebrafish nonneural ectoderm lend support to the existence of such non-axial signaling in the A/P axis. Thus we find that the earliest expression of GATA-2 and 3 is located in nonneural ectoderm and is strongly patterned in a graded manner along the A/P axis, being high anteriorly and absent from the most posterior regions. This results by early neurula stages in three broad zones: an anterior region which is positive for both GATA-2 and 3, a middle region which is positive for GATA-2 alone and a posterior region in which neither gene is expressed. These regions correspond to head, trunk and tail ectoderm and may represent the beginnings of functional segmentation of nonneural ectoderm, as suggested in the concept of the 'ectomere'. We find that A/P patterning of GATA expression in nonneural ectoderm may occur as early as late blastula/early gastrula stages. We investigate which posteriorizing signals might contribute to such distinct non axial ectodermal patterning in the A/P axis and provide evidence that both FGF and a Wnt family member contribute towards the final A/P pattern of GATA expression in nonneural ectoderm.

PubMed ID: 9727832
Article link: Int J Dev Biol
Grant support: [+]

Species referenced: Xenopus
Genes referenced: acta2 dlx3 egf egr2 fgf4 gata2 gata3 hoxa7 hoxb9 hoxc9-like kit ncam1 otx2 pax2 snai2 tbxt

Article Images: [+] show captions