XB-ART-6561Development 2002 Oct 01;12919:4387-97. doi: 10.1242/dev.129.19.4387.
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Cement gland-specific activation of the Xag1 promoter is regulated by co-operation of putative Ets and ATF/CREB transcription factors.
The cement gland marks the extreme anterior ectoderm of the Xenopus embryo, and is determined through the overlap of several positional domains. In order to understand how these positional cues activate cement gland differentiation, the promoter of Xag1, a marker of cement gland differentiation, was analyzed. Previous studies have shown that Xag1 expression can be activated by the anterior-specific transcription factor Otx2, but that this activation is indirect. 102 bp of upstream genomic Xag1 sequence restricts reporter gene expression specifically to the cement gland. Within this region, putative binding sites for Ets and ATF/CREB transcription factors are both necessary and sufficient to drive cement gland-specific expression, and cooperate to do so. Furthermore, while the putative ATF/CREB factor is activated by Otx2, a factor acting through the putative Ets-binding site is not. These results suggest that Ets-like and ATF/CREB-like family members play a role in regulating Xag1 expression in the cement gland, through integration of Otx2 dependent and independent pathways.
PubMed ID: 12223398
Article link: Development
Species referenced: Xenopus laevis
Genes referenced: ag1 creb1 otx2
Article Images: [+] show captions
|Fig. 2. Upstream genomic Xag1 sequence drives cement gland-specific expression. In situ hybridization for endogenous Xag1 (A,B) or gfp transcripts (C,E-J) in early neurula (A,C,E,G) or tailbud (B,F,H-J) embryos. (D) GFP fluorescence in a transgenic tailbud embryo. Endogenous Xag1 is expressed at the anterior of the embryo from the end of gastrulation (A) in the cement gland (black arrowhead) and hatching gland primordia (black arrow), and in the cement gland (white arrowhead) and hatching gland (white arrow) in the tailbud embryo (B). This expression pattern is replicated by 8 kb of Xag1 genomic sequence driving a GFP reporter gene (C,D). (E-H) Cement gland-specific gfp expression is driven from early neurula stages by –275 bp (E,F) and –102 bp (G,H), but not 73 bp of upstream sequence (I) or the Xag1 TATA box (J) (arrowheads indicate location of cement gland). Expression is weaker with the –102 bp construct (G,H) than with the longer –275 bp construct (E,H), especially at neurula stages (arrowheads). Po, posterior; np, neural plate.|