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Dev Biol 2004 Jul 15;2712:322-38. doi: 10.1016/j.ydbio.2004.03.036.
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Proximo-distal specialization of epithelial transport processes within the Xenopus pronephric kidney tubules.

The embryonic kidneys of larval aquatic vertebrates such as fish and frogs serve as excellent model systems for exploring the early development of nephric organs. These experimental systems can easily be manipulated by microsurgery, microinjection, genetics, or combinations of these approaches. However, little is known about how physiologically similar these simple kidneys are to the more complex mammalian adult kidneys. In addition, almost nothing is known about proximo-distal patterning of nephrons in any organism. In order begin to explore the physiological specialization of the pronephric tubules along the proximo-distal axis, a combination of uptake assays using fluorescently tagged proteins, LDL particles and dextrans, and an informatics-targeted in situ screen for transport proteins have been performed on embryos of the frog, Xenopus laevis. Genes identified to be expressed within unique subdomains of the pronephric tubules include an ABC transporter, two amino acid cotransporters, two sodium bicarbonate cotransporters, a novel sodium glucose cotransporter, a sodium potassium chloride cotransporter (NKCC2), a sodium chloride organic solute cotransporter (ROSIT), and a zinc transporter. A novel combination of colorimetric and fluorescent whole-mount in situ hybridization (FCIS) was used to precisely map the expression domain of each gene within the pronephros. These data indicate specialized physiological function and define multiple novel segments of the pronephric tubules, which contain at least six distinct transport domains. Uptake studies identified functional transport domains and also demonstrated that early glomeral leakage can allow visualization of protein movement into the pronephric tubules and thus establish a system for investigating experimentally induced proteinuria and glomerulonephritis.

PubMed ID: 15223337
Article link: Dev Biol

Species referenced: Xenopus laevis
Genes referenced: abcf2 adm atp1a1 slc12a1 slc30a1 slc4a11 slc4a4 slc5a9 slc6a14 slc6a14.2 slc6a19 slc7a8

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