PubMed 21262879

Title: Functional and developmental expression of a zebrafish Kir1.1 (ROMK) potassium channel homologue Kcnj1.

Authors: Leila Abbas, Saeed Hajihashemi, Lucy F Stead, Gordon J Cooper, Tracy L Ware, Tim S Munsey, Tanya T Whitfield, Stanley J White

Journal, date & volume: J. Physiol. (Lond.), 2011 Mar 15 , 589, 1489-503

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The zebrafish, Danio rerio, is emerging as an important model organism for the pathophysiological study of some human kidney diseases, but the sites of expression and physiological roles of a number of protein orthologues in the zebrafish nephron remain mostly undefined. Here we show that a zebrafish potassium channel is orthologous to the mammalian kidney potassium channel, ROMK. The cDNA (kcnj1) encodes a protein (Kcnj1) that when expressed in Xenopus laevis oocytes displayed pH- and Ba2+-sensitive K+-selective currents, but unlike the mammalian channel, was completely insensitive to the peptide inhibitor tertiapin-Q. In the pronephros, kcnj1 transcript expression was restricted to a distal region and overlapped with that of sodium–chloride cotransporter Nkcc, chloride channel ClC-Ka, and ClC-Ka/b accessory subunit Barttin, indicating the location of the diluting segment. In a subpopulation of surface cells, kcnj1 was coexpressed with the a1a.4 isoform of the Na+/K+-ATPase, identifying these cells as potential K+ secretory cells in this epithelium. At later stages of development, kcnj1 appeared in cells of the developing gill that also expressed the a1a.4 subunit.Morpholino antisense-mediated knockdown of kcnj1 was accompanied by transient tachycardia followed by bradycardia, effects consistent with alterations in extracellular K+ concentration in the embryo.Our findings indicate that Kcnj1 is expressed in cells associated with osmoregulation and acts as a K+ efflux pathway that is important in maintaining extracellular levels of K+ in the developing embryo.