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V-ATPase-dependent ectodermal voltage and pH regionalization are required for craniofacial morphogenesis.

ABSTRACT: Using voltage and pH reporter dyes, we have discovered a never-before-seen regionalization of the Xenopus ectoderm, with cell subpopulations delimited by different membrane voltage and pH. We distinguished three courses of bioelectrical activity. Course I is a wave of hyperpolarization that travels across the gastrula. Course II comprises the appearance of patterns that match shape changes and gene expression domains of the developing face; hyperpolarization marks folding epithelium and both hyperpolarized and depolarized regions overlap domains of head patterning genes. In Course III, localized regions of hyperpolarization form at various positions, expand, and disappear. Inhibiting H(+) -transport by the H(+) -V-ATPase causes abnormalities in: (1) the morphology of craniofacial structures; (2) Course II voltage patterns; and (3) patterns of sox9, pax8, slug, mitf, xfz3, otx2, and pax6. We conclude that this bioelectric signal has a role in development of the face. Thus, it exemplifies an important, under-studied mechanism of developmental regulation.

SUBMITTER: Vandenberg LN

PROVIDER: S-EPMC10277013 | biostudies-literature | 2011 Aug

REPOSITORIES: biostudies-literature

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V-ATPase-dependent ectodermal voltage and pH regionalization are required for craniofacial morphogenesis.

Vandenberg Laura N LN Morrie Ryan D RD Adams Dany Spencer DS

Developmental dynamics : an official publication of the American Association of Anatomists 20110801 8

Using voltage and pH reporter dyes, we have discovered a never-before-seen regionalization of the Xenopus ectoderm, with cell subpopulations delimited by different membrane voltage and pH. We distinguished three courses of bioelectrical activity. Course I is a wave of hyperpolarization that travels across the gastrula. Course II comprises the appearance of patterns that match shape changes and gene expression domains of the developing face; hyperpolarization marks folding epithelium and both hyp ...[more]

PMID: 21761475

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Project description:Whereas electrogenic partial reactions of the Na,K-ATPase have been studied in depth, much less is known about the influence of the membrane potential on the electroneutrally operating gastric H,K-ATPase. In this work, we investigated site-specifically fluorescence-labeled H,K-ATPase expressed in Xenopus oocytes by voltage clamp fluorometry to monitor the voltage-dependent distribution between E(1)P and E(2)P states and measured Rb(+) uptake under various ionic and pH conditions. The steady-state E(1)P/E(2)P distribution, as indicated by the voltage-dependent fluorescence amplitudes and the Rb(+) uptake activity were highly sensitive to small changes in intracellular pH, whereas even large extracellular pH changes affected neither the E(1)P/E(2)P distribution nor transport activity. Notably, intracellular acidification by approximately 0.5 pH units shifted V(0.5), the voltage, at which the E(1)P/E(2)P ratio is 50∶50, by -100 mV. This was paralleled by an approximately two-fold acceleration of the forward rate constant of the E(1)P→E(2)P transition and a similar increase in the rate of steady-state cation transport. The temperature dependence of Rb(+) uptake yielded an activation energy of ∼90 kJ/mol, suggesting that ion transport is rate-limited by a major conformational transition. The pronounced sensitivity towards intracellular pH suggests that proton uptake from the cytoplasmic side controls the level of phosphoenzyme entering the E(1)P→E(2)P conformational transition, thus limiting ion transport of the gastric H,K-ATPase. These findings highlight the significance of cellular mechanisms contributing to increased proton availability in the cytoplasm of gastric parietal cells. Furthermore, we show that extracellular Na(+) profoundly alters the voltage-dependent E(1)P/E(2)P distribution indicating that Na(+) ions can act as surrogates for protons regarding the E(2)P→E(1)P transition. The complexity of the intra- and extracellular cation effects can be rationalized by a kinetic model suggesting that cations reach the binding sites through a rather high-field intra- and a rather low-field extracellular access channel, with fractional electrical distances of ∼0.5 and ∼0.2, respectively.

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Dataset Information

V-ATPase-dependent ectodermal voltage and pH regionalization are required for craniofacial morphogenesis.

Publications

V-ATPase-dependent ectodermal voltage and pH regionalization are required for craniofacial morphogenesis.

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