Expression of xSDF-1α, xCXCR4, and xCXCR7 during gastrulation in Xenopus laevis.

Chemokines play a crucial role in developmental processes and recent studies have revealed that they also control gastrulation movements. In this paper, we report the expression patterns of xSDF-1α, xCXCR4 and xCXCR7 and regulation of the expression of xSDF-1α and xCXCR4 during gastrulation. We performed whole mount in situ hybridization (WISH) and quantitative real-time RT-PCR (qRT-PCR) analyses to examine the distribution of transcripts. The effect of activin/nodal signaling on the expression of xSDF-1α and its receptors was examined by animal cap assay and microinjection of cer-s mRNA. We have demonstrated that the xSDF-1αtranscript is increased in the blastocoel roof during gastrulation, but not in the involuted mesoderm. xCXCR4 was expressed in the mesendoderm at late blastula and was retained throughout gastrulation. xCXCR7 was found in the dorsal lip around the blastopore in the early gastrula stage and became localized in the presumptive notochord later. We also show that the expression of xCXCR4 and xSDF-1transcript is increased in the blastocoel roof during gastrulation, but not in the involuted mesoderm. xCXCR4 was expressed in the mesendoderm at late blastula and was retained throughout gastrulation. xCXCR7 was found in the dorsal lip around the blastopore in the early gastrula stage and became localized in the presumptive notochord later. We also show that the expression of xCXCR4 and xSDF-1α were reciprocally regulated by activin/nodal signaling. These results suggest that xSDF-1α and its receptors contribute to the cell arrangement of mesoderm cells and their expression patterns are partially regulated by activin/nodal signaling.