Biomedical subjects

Jun-ichi Kyuno

Publications and source records attributed to Jun-ichi Kyuno.

4 recordsLinked to original sources

PubMed2006

GDNF expression during Xenopus development.

Glial cell line-derived neurotrophic factor (GDNF) has multiple roles in kidney morphogenesis, spermatogenesis, and neurogenesis during development. In this study, we report the cloning and expression pattern of Xenopus laevis GDNF. The X. laevis GDNF cDNA sequence has a complete open reading frame of 684 bases, predicting 227 amino acid residues at the protein level. Comparison of the X. laevis GDNF amino acid sequence with those of chick, human, mouse, rat and zebrafish indicates that X. laevis GDNF has 60%-52% and 75%-62% identity over the whole amino acid sequence and for the putative mature forms, respectively. All known functional motifs of GDNF were conserved in the X. laevis sequence. Temporal expression analysis by RT-PCR indicated that GDNF transcripts were first detectable at stage 12 at a low level, and gradually increased up to stage 22. From stage 24, the expression sharply increased and continued at a similar level as development progressed. Spatial expression analysis by whole-mount in situ hybridization showed that the GDNF mRNA was predominantly detected in somites, pronephros, pharyngeal arches, epibranchial placodes, digestive tract and some of the lateral line structure. These results suggest that this X. laevis gene is the orthologue for GDNF.

Amino Acid Sequence↗

PubMed2003

Identification and characterization of Xenopus NDRG1.

NDRG1 is a member of the N-myc downstream-regulated gene (NDRG) family and is involved in cellular differentiation, activation of p53, cell cycle arrest, metastasis, and hypoxia. Expression of NDRG1 is repressed by the proto-oncogene, N-myc during mouse development, although the exact functional role of NDRG1 in development remains unknown. Here, we report the characterization of Xenopus laevis NDRG1 (xNDRG1) during X. laevis development. Expression of xNDRG1 transcript was first detected at stage 15, and was localized to the presumptive pronephric anlagen at stage 26 and to pronephros, eye, branchial arches, and tail-bud at stage 32. Overexpression of xNDRG1 results in a reduced pronephros and disorganized somites. Depletion of xNDRG1, using morpholinos, causes failure of pronephros development. These results suggest that xNDRG1 is required for pronephros development in X. laevis.

Amino Acid Sequence↗

PubMed2003

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.

Animals↗

PubMed2002

Role of the thrombopoietin (TPO)/Mpl system: c-Mpl-like molecule/TPO signaling enhances early hematopoiesis in Xenopus laevis.

Multiple organs are induced in the primitive embryonic ectoderm excised from blastula stage Xenopus laevis embryos, under the strict control of mesoderm inducing factors. This in vitro system is useful for exploring the mechanisms of development. In this study, the function of thrombopoietin (TPO)/c-Mpl signaling in the development of hematopoietic cells was investigated. An optimal hematopoietic cell induction system was established to evaluate the influence of growth factors on hematopoiesis. It was found that exogenous TPO enhanced hematopoiesis in explants induced by activin and bone morphogenetic protein (BMP)-4 and increased the number of both erythrocytes and leukocytes in a dose-dependent manner. Addition of anti-c-Mpl antibody completely inhibited the expansion of hematopoietic cells stimulated by TPO, and the antibody specifically recognized blood-like cells. These results demonstrate that TPO acts on hematopoietic progenitors induced in explants and the c-Mpl-like molecule in Xenopus mediates the cellular function of TPO. We also found that forced expression of TPO in embryos promoted hematopoiesis in the ventral blood island and the dorsal-- lateral plate mesoderm. These results suggest that hematopoietic stem and progenitor cells are regulated by TPO/c-Mpl signaling from when they appear in their ontogeny. They also suggest that TPO/c-Mpl signaling play a crucial role in the formation of hematopoietic cells in Xenopus.

Animals↗