Trb2, a mouse homolog of tribbles, is dispensable for kidney and mouse development

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Abstract

Glomeruli comprise an important filtering apparatus in the kidney and are derived from the metanephric mesenchyme. A nuclear protein, Sall1, is expressed in this mesenchyme, and we previously reported that Trb2, a mouse homolog of Drosophila tribbles, is expressed in the mesenchyme-derived tissues of the kidney by microarray analyses using Sall1-GFP knock-in mice. In the present report, we detected Trb2 expression in a variety of organs during gestation, including the kidneys, mesonephros, testes, heart, eyes, thymus, blood vessels, muscle, bones, tongue, spinal cord, and ganglions. In the developing kidney, Trb2 signals were detected in podocytes and the prospective mesangium of the glomeruli, as well as in ureteric bud tips. However, Trb2 mutant mice did not display any apparent phenotypes and no proteinuria was observed, indicating normal glomerular functions. These results suggest that Trb2 plays minimal roles during kidney and mouse development.

Section snippets

Materials and methods

Generation of Trb2 mutant mice. The homologous arms of the targeting vector were isolated using the Red/ET recombination cloning system (Gene Bridges GmbH) and a bacterial artificial chromosome (BAC) clone obtained from the C57BL/6 library. The 5′arm (8.3 kb) was obtained using the primers 5′-AACCCAGCCAGCAGCTCCAGAATT-3′ and 5′-GCTCATCCATCTCTCCAGAGGGGTT-3′, while the 3′ arm (4.1 kb) was obtained using 5′-AGACTCCCGGGATCATTATGCGTG-3′ and 5′-TCTGCCTGTCTGCCCATAGCAACAT-3′. The 5′ arm was cloned into

Generation of Trb2 mutant mice

To examine the roles of Trb2 in vivo, we generated Trb2 mutant mice using embryonic stem cells. The Trb2 gene is composed of three exons, and exon 1 includes the first ATG site. We replaced a portion of exon 1 including 44 base pairs upstream of the initiation codon with the LacZ-Neo cassette, which consists of a β-galactosidase gene and a neomycin-resistance gene sandwiched by lox71 and loxP sequences (Fig. 1A). Southern blotting analysis and genomic PCR confirmed correct homologous

Discussion

Trb2 is a mouse homolog of Drosophila tribbles. By generating Trb2-lacZ mutant mice, we showed that Trb2 is expressed in the podocytes of developing kidney glomeruli, as well as in many other tissues. However, homozygous mice did not exhibit any apparent phenotypes. Glomeruli were formed and no proteinuria was observed, suggesting normal podocyte functions in the absence of Trb2. Our data indicate that Trb2 has minimal functions in kidney and mouse development.

We detected Trb2 expression in a

Acknowledgments

We thank H. Kobayashi for helpful discussions. This work was supported in part by the Ministry of Education, Culture, Sports, Science and Technology and by the Ministry of Health, Labor and Welfare of Japan. Minoru Takasato was supported by the Japan Society for the Promotion of Science.

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