Visualization in zebrafish larvae of Na+ uptake in mitochondrion-rich cells whose differentiation is dependent on foxi3{alpha}

Esaki, M., Hoshijima, K., Kobayashi, S., Fukuda, H., Kawakami, K., and Hirose, S.
American journal of physiology. Regulatory, integrative and comparative physiology   292(1): R470-R480 (Journal)
Registered Authors
Hoshijima, Kazuyuki, Kawakami, Koichi
chloride cell, Sodium Green, Na+/H+ exchanger, vacuolar-type H+-ATPase
MeSH Terms
  • Animals
  • Calcium/physiology
  • Cation Transport Proteins/antagonists & inhibitors
  • Cell Differentiation/drug effects
  • Hepatocyte Nuclear Factor 3-gamma/genetics*
  • Image Processing, Computer-Assisted
  • Immunohistochemistry
  • In Situ Hybridization
  • Larva/physiology*
  • Mitochondria/metabolism*
  • Morpholines/pharmacology
  • Oligonucleotides, Antisense/pharmacology
  • Organic Chemicals
  • Proton-Translocating ATPases/metabolism
  • Sodium/metabolism*
  • Sodium Radioisotopes
  • Sodium-Hydrogen Exchangers/metabolism
  • Yolk Sac/cytology
  • Yolk Sac/metabolism
  • Zebrafish/physiology*
16946087 Full text @ Am. J. Physiol. Regul. Integr. Comp. Physiol.
Uptake of Na(+) from the environment is an indispensable strategy for the survival of freshwater fish, as they easily lose Na(+) from the plasma to a diluted environment. Nevertheless, the location of, and molecules involved in Na(+) uptake remain poorly understood. In this study, we utilized Sodium Green, a Na(+)-dependent fluorescent reagent, to provide direct evidence that Na(+) absorption takes place in a subset of the mitochondrion-rich (MR) cells on the yolk sac surface of zebrafish larvae. Combined with immunohistochemistry, we revealed that the Na(+)-absorbing MR cells were exceptionally rich in vacuolar-type H(+)-ATPase (H(+)-ATPase) but moderately rich in Na(+)/K(+)-ATPase. We also addressed the function of foxi3alpha transcription factor that is specifically expressed in the H(+)-ATPase-rich MR cells. When foxi3alpha was depleted from zebrafish embryos by antisense morpholino oligonucleotide injection, differentiation of the MR cells was completely blocked and Na(+) influx was severely reduced, indicating that MR cells are the primary sites for Na(+) absorption. Additionally, foxi3alpha expression is initiated at gastrula stage in the presumptive ectoderm; thus we propose that foxi3alpha is a key gene in the control of MR cell differentiation. We also utilized a set of ion transport inhibitors to assess the molecules involved in the process and discuss the observations. Key words: chloride cell, mitochondria-rich cell, Sodium Green, Na+/H+ exchanger (NHE), vacuolar-type H+-ATPase.
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Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Engineered Foreign Genes