Organization of the pronephric kidney revealed by large-scale gene expression mapping.
BACKGROUND
The pronephros, the simplest form of a vertebrate excretory organ, has recently become an important model of vertebrate kidney organogenesis. Here, we elucidated the nephron organization of the Xenopus pronephros and determined the similarities in segmentation with the metanephros, the adult kidney of mammals.


RESULTS
We performed large-scale gene expression mapping of terminal differentiation markers to identify gene expression patterns that define distinct domains of the pronephric kidney. We analyzed the expression of over 240 genes, which included members of the solute carrier, claudin, and aquaporin gene families, as well as selected ion channels. The obtained expression patterns were deposited in the searchable European Renal Genome Project Xenopus Gene Expression Database. We found that 112 genes exhibited highly regionalized expression patterns that were adequate to define the segmental organization of the pronephric nephron. Eight functionally distinct domains were discovered that shared significant analogies in gene expression with the mammalian metanephric nephron. We therefore propose a new nomenclature, which is in line with the mammalian one. The Xenopus pronephric nephron is composed of four basic domains: proximal tubule, intermediate tubule, distal tubule, and connecting tubule. Each tubule may be further subdivided into distinct segments. Finally, we also provide compelling evidence that the expression of key genes underlying inherited renal diseases in humans has been evolutionarily conserved down to the level of the pronephric kidney.


CONCLUSIONS
The present study validates the Xenopus pronephros as a genuine model that may be used to elucidate the molecular basis of nephron segmentation and human renal disease.
Raciti
Daniela
D
Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, ETH Zürich, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland. daniela.raciti@access.uzh.ch
Reggiani
Luca
L
Geffers
Lars
L
Jiang
Qiuhong
Q
Bacchion
Francesca
F
Subrizi
Astrid E
AE
Clements
Dave
D
Tindal
Christopher
C
Davidson
Duncan R
DR
Kaissling
Brigitte
B
Brändli
André W
AW
D000328:Adult; D000818:Animals; D015415:Biomarkers; D002454:Cell Differentiation; D027963:Chloride-Bicarbonate Antiporters / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007668:Kidney / Q000033:anatomy & histology / Q000196:embryology* / Q000378:metabolism; D007674:Kidney Diseases / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D029867:Xenopus Proteins / Q000235:genetics; D014982:Xenopus laevis / Q000235:genetics
D015415:Biomarkers; D027963:Chloride-Bicarbonate Antiporters; D029867:Xenopus Proteins