ZFIN ID: ZDB-PUB-200522-10
The Rhesus glycoprotein Rhcgb is expendable for ammonia excretion and Na+ uptake in zebrafish (Danio rerio)
Zimmer, A.M., Perry, S.F.
Date: 2020
Source: Comparative biochemistry and physiology. Part A, Molecular & integrative physiology   247: 110722 (Journal)
Registered Authors: Perry, Steve F.
Keywords: Clustered regularly-interspaced palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9), H(+)-ATPase-rich (HR) cell, High external ammonia (HEA), Ionocyte, Ionoregulation, Na(+)/H(+) exchanger 3b (Nhe3b)
MeSH Terms:
  • Ammonia/metabolism*
  • Animals
  • Biological Transport
  • Cation Transport Proteins/genetics
  • Cation Transport Proteins/metabolism*
  • Gills/metabolism*
  • Larva
  • Sodium/metabolism*
  • Sodium-Hydrogen Exchangers/metabolism
  • Zebrafish/genetics
  • Zebrafish/metabolism*
  • Zebrafish Proteins/genetics
  • Zebrafish Proteins/metabolism*
PubMed: 32437959 Full text @ Comp. Biochem. Physiol. A Mol. Integr. Physiol.
ABSTRACT
In zebrafish (Danio rerio), the ammonia-transporting Rhesus glycoprotein Rhcgb is implicated in mechanisms of ammonia excretion and Na+ uptake. In particular, Rhcgb is thought to play an important role in maintaining ammonia excretion in response to alkaline conditions and high external ammonia (HEA) exposure, in addition to facilitating Na+ uptake via a functional metabolon with the Na+/H+-exchanger Nhe3b, specifically under low Na+ conditions. In the present study, we hypothesized that CRISPR/Cas9 knockout of rhcgb would reduce ammonia excretion and Na+ uptake capacity, particularly under the conditions listed above that have elicited increases in Rhcgb-mediated ammonia excretion and/or Na+ uptake. Contrary to this hypothesis, however, larval and juvenile rhcgb knockout (KO) mutants showed no reductions in ammonia excretion or Na+ uptake under any of the conditions tested in our study. In fact, under control conditions, rhcgb KO mutants generally displayed an increase in ammonia excretion, potentially due to increased transcript abundance of another rh gene, rhbg. Under alkaline conditions, rhcgb KO mutants were also able to maintain ammonia excretion, similar to wild-type fish, and stimulation of ammonia excretion after HEA exposure also was not affected by rhcgb KO. Surprisingly, ammonia excretion and Na+ uptake were unaffected by rhcgb or nhe3b KO in juvenile zebrafish acclimated to normal (800 μmol/L) or low (10 μmol/L) Na+ conditions. These results demonstrate that Rhcgb is expendable for ammonia excretion and Na+ uptake in zebrafish, highlighting the plasticity and flexibility of these physiological systems in this species.
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