Characterization of a gene respondent to clinorotation in Xenopus A6 cells

The A6 epithelial cell line, derived from the kidney of Xenopus laevis, spontaneously form domes after it has reached confluence. In a previous study, we demonstrated that formation of domes is strongly inhibited in the cells cultured using a three-dimensional clinostat. In this study, we performed staining of filamentous actin and examination using electron microscopy to investigate morphological changes of A6 cells exposured to clinorotation for 10 days. Micrographs show that A6 cells in clinorotation lose cortical actin that is characteristic of epithelial cells. Therefore, we search for genes differentially expressed in A6 cells cultured in clinorotation and identified Xenopus laevis N-myc downstream-regulated gene-1 (xNDRG1) as a clinorotation respondent gene in A6 cells. In northern blots analysis, xNDRG1 mRNA significantly increased only in A6 cells cultured in clinorotation for 10 days, and maintained at a similar level in the cells cultured for 15 days. Centrifugations of A6 cells have no effect on expression of xNDRG1. We also aimed to characterize xNDRG1 during Xenopus laevis development by examining the temporal and spatial expression patterns of xNDRG1 transcripts in embryos. Our results suggest that xNDRG1 is necessary for pronephros development in Xenopus laevis.