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Gene Expr Patterns
2007 Oct 01;78:852-7. doi: 10.1016/j.neuint.2007.07.003.
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Xenopus galectin-VIa shows highly specific expression in cement glands and is regulated by canonical Wnt signaling.
Abstract Anterior-posterior neural patterning of Xenopus embryo is determined during gastrulation and then followed by differentiation of neural structures including brain and eye. The cement gland is a mucus-secreting neural organ located in the anterior end of the neural plate. This study analyzed expression patterns of Xenopus galectin-VIa (Xgalectin-VIa) by whole-mount in situ hybridization, and found highly restricted expression of this gene in the cement gland region. These patterns were similar to those of XAG-1 and XCG, known cement gland-specific genes. In addition, Xgalectin-VIa was expressed in the dorsal edge of eye vesicles, the otic vesicle, and in part of the hatching gland at the tadpole stage. Although the spatial expression pattern was similar, the temporal expression of Xgalectin-VIa differed from that of XAG-1 and XCG. RT-PCR analysis showed only weak Xgalectin-VIa expression in early neurula embryos, whereas both XAG-1 and CGS were strongly expressed at that stage. We also showed that Xgalectin-VIa expression is repressed by enhancement of Wnt signaling and increased by its inhibition. Furthermore, Xgalectin-VIa expression was activated by neural-gene inducer Xotx2, as is the case for XAG-1 and CGS. Together, these results indicated that Xgalectin-VIa possesses different features from other cement gland genes and is a novel and useful marker of the cement gland in developing embryos.
Fig. 1. Spatial pattern of Xgalectin-VIa (A,B,C,J,K,L,M,N,O), XCG (D,E,F,Q) and XAG-1 (G,H,I,P) expression by whole-mount in situ ybridization. (A,D,G) Anterior views of the early neurula. Dorsal side is up. (B,E,H) Anterior views of the late neurula. (C,F,I) Lateral views of the tailbud. Xgalectin-VIa was expressed in a highly specific pattern in the cement gland region. (Jâ L) Spatial pattern of Xgalectin-VIa expression at late-tailbud (J) and tadpole (K,L) stages. CG, cement gland; eye, eye vesicle; OV, otic vesicle. (M,N) Histological section of (l). Sectioned regions are indicated in (l). (Oâ Q) Comparison of Xgalectin-VIa expression patterns (O) with those of XAG-1 (P) and XCG (Q) in the anterior region of tadpole-stage embryos. Xgalectin-VIa was expressed in hatching gland (HG; indicated with arrowhead), as observed for XAG-1.
Fig. 3. Effect of canonical Wnt signaling on Xgalectin-VIa expression. (A) 500 pg of β-catenin (βcat) mRNA (lane 1), 250 pg (lane 2) of βcat mRNA, 500 pg of lacZ (lane 3), 20 ng of standard control morpholino antisense oligo (CMO; lane 4), 10 ng of β-catenin MO (βcatMO; lane 5), and 20 ng of βcatMO (lane 6) were injected into animal poles of 8-cell embryos, followed by RT-PCR analysis with cDNAs derived from these whole embryos. The order reflects the gradient of canonical Wnt signaling. Similar to XAG-1 and XCG, Xgalectin-VIa expression was decreased by βcat mRNA (lanes 1, 2) and increased by βcatMO (lanes 5, 6). (B–J) Effects of βcat mRNA or βcatMO injection on Xgalectin, XAG-1, and XCG expression were also examined by WISH. 500 pg of lacZ mRNA (B,E,H), 500 pg of lacZ mRNA and 500 pg of βcat mRNA (C,F,I), or lacZ mRNA and 20 ng of βcatMO (D,G,J) were injected into the animal pole region of 8-cell embryos. After active staining with RED-Gal at stage 18, WISH was carried out with probes for Xgalectin-VIa (B,C,D), XAG-1 (E,F,G), and XCG (H,I,J). In all cases, βcat mRNA injection caused loss of gene expression (C,F,I). Conversely, βcatMO injection induced ectopic expressions (D,G,J; arrowhead).
