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Figure 1. Segmental organization of the Xenopus pronephric nephron. (A) Spatial expression patterns of selected pronephric marker genes. Xenopus embryos (stage 35/36) were stained by whole-mount in situ hybridization for expression of clcnk (ClC-K), fxyd2 (Na, K-ATPase γ subunit), pax2, slc5a2 (SGLT2), slc5a11 (SGLT1L), slc7a13, slc12a1 (NKCC2), and slc12a3 (NCC). Lateral views are shown with accompanying enlargements of the pronephric kidney region. (B) Summary of marker gene expression along the proximodistal axis of the pronephric nephron. The localization of the expression domains is shown below the corresponding segments. (C) Schematic representation of the tubular portion of the Xenopus pronephric kidney. A stage 35/36 pronephric kidney is shown with the four tubular compartments color-coded. Each tubule may be further subdivided into distinct segments: proximal tubule (yellow; PT1, PT2, PT3), intermediate tubule (green; IT1, IT2, IT3), distal tubule (orange; DT1, DT2), and connecting tubule (gray; CT). The nephrostomes (NS) are ciliated peritoneal funnels that connect the coelomic cavity to the nephron. |
