ZFIN ID: ZDB-PUB-071210-8
Zebrafish Ae2.2 encodes a second Slc4a2 anion exchanger
Shmukler, B.E., Clark, J.S., Hsu, A., Vandorpe, D.H., Stewart, A.K., Kurschat, C.E., Choe, S.K., Zhou, Y., Amigo, J., Paw, B.H., and Alper, S.L.
The genome of zebrafish D. rerio encodes two unlinked genes equally closely related to the SLC4A2/AE2 anion exchanger genes of mammals. One of these is the recently reported zebrafish Ae2 gene (Shmukler et al., Am J Physiol Renal Physiol 289:R835, 2005), now called Ae2.1. We now report the structural and functional characterization of the second zebrafish AE2 gene product, Ae2.2. The Ae2.2 gene of zebrafish LG24 encodes a polypeptide of 1232 aa in length, sharing 70% amino acid identity with zebrafish Ae2.1 and 67% identity with mouse AE2a. Zebrafish Ae2.2 expressed in Xenopus oocytes encodes a 135 kDa polypeptide that mediates bidirectional, DIDS-sensitive Cl(-)/Cl(-) exchange and Cl(-)/HCO3(-) exchange. Ae2.2-mediated Cl(-)/Cl(-) exchange is cation-independent, voltage-insensitive, and electroneutral. Acute regulation of anion exchange mediated by Ae2.2 includes activation by NH4(+) and independent inhibition by acidic intracellular pH (pHi) and by acidic extracellular pH (pHo). In situ hybridization reveals low-level expression of Ae2.2 mRNA in zebrafish embryo, most notably in posterior tectum, eye, pharynx, epidermal cells, and axial vascular structures, without notable expression in the Ae2.1-expressing pronephric duct. Knockdown of Ae2.2 mRNA, of Ae2.1 mRNA, or of both with nontoxic levels of N-morpholino-oligomers produced no grossly detectable morphological phenotype, and preserved normal structure of the head and the pronephric duct at 24 hpf. Key words: Chloride/bicarbonate exchanger, Xenopus oocyte, isotopic flux, in situ hybridization, N-morpholino oligomer.