Role of zebrafish ClC‐K/barttin channels in apical kidney chloride reabsorption

Abstract

Key pointsr We have characterized the zebrafish clc-k and barttin proteins, demonstrating that they form a protein complex mediating chloride flux in a similar manner to their mammalian counterparts.r As in mammals, in zebrafish, clc-k and barttin are basically expressed in the kidney. Contrary to what is found in mammals, in zebrafish both proteins show an apical localization in the kidney.r We have generated the first knockout in zebrafish of a CLC protein. Lack of clc-k in zebrafish resulted in embryonic lethality, possibly caused by a reduction in total chloride content. As a consequence, there is an up-regulation of other chloride channels and other regulatory mechanisms such as renin or the uro-guanylin receptor in the kidney. r barttin is mislocalized in vivo when clc-k is not present, indicating that there is a mutual dependence of the protein expression and localization between barttin and clc-k proteins.Abstract ClC-K/barttin channels are very important for salt transport in the kidney. This function can be clearly seen since mutations in CLCNKB or BSND cause Bartter's syndrome types III and IV, respectively. Working with the freshwater teleost zebrafish, we characterized the genes homologous to the mammalian chloride channel ClC-K and its obligate subunit barttin and we obtained and studied clc-k knockout zebrafish. The zebrafish clc-k/barttin proteins are very similar to their mammalian counterparts, and both proteins are necessary to mediate chloride currents. Localization studies indicated that both proteins are exclusively expressed in the apical membranes of zebrafish kidney tubules. Knockout of clc-k resulted in embryonic lethality. These animals showed barttin mislocalization and a reduction in whole-body chloride concentration, Carla Pérez received her degree in Biotechnology from the University of Vic, Spain. She obtained her Master's Degree in Neuroscience from the University of Barcelona, Spain, and joined the Physiology and Pathology of The Functional Relationship Between Glia and Neurons Group at the same University. There, she obtained her PhD by studying the physiology of zebrafish ClC chloride channels and their associated diseases. Aida Castellanos received her degree in Biology from the University of Girona, Spain. She subsequently got her Master's Degree in Neuroscience from the University of Barcelona, Spain, and then joined the Neurophysiology Group at the same University. After getting her PhD in the field of somatosensation and pain, she currently holds a postdoctoral position at the Physiology Group of the University of Barcelona, where she studies the physiopathological relationship between glia and neurons, with a particular interest in rare diseases. C. P.-Rius and A. Castellanos contributed equally to this work.3970 C. Pérez-Rius and others J Physiol 597.15as well as up-regulation of the expression of other chloride channels and renin, and an increase in the kidney expression of the uroguanylin receptor. Our results indicate that apical kidney chloride reabsorption through c...

Modelling salt transport disorders of human kidney in zebrafish: the grain of salt

“…At first, the study of Pérez‐Rius et al . () found that zfclc‐k was expressed almost exclusively in the kidney. The in situ hybridization showed that zfclc‐k was located in the distal segment of the pronephros 24 h after fertilization.…”

“…In a recent issue of The Journal of Physiology , Pérez‐Rius et al . () investigated the function of clc‐k–the only zebrafish orthologue of ClC‐Ka and ClC‐Kb–in kidney chloride reabsorption. This study found that clc‐k knockout caused lethality in zebrafish.…”

“…This short review will use the study of Pérez‐Rius et al . () as a case to discuss the opportunity and the caveat for modelling salt transport disorders of human kidney in zebrafish.…”

“…The study of Pérez‐Rius et al . () pointed out similarities between zfclc‐k and its human orthologues: (i) dominant expression in the kidney; (ii) the association with auxiliary subunit barttin; and (iii) barttin regulates the cellular localization and function of the protein. At first, the study of Pérez‐Rius et al .…”

“…The study of Pérez‐Rius et al . () demonstrated the spatial association of zfclc‐k and zebrafish barttin (zfbarttin) both in vitro and in vivo . In HEK293T cells, the presence of zfbarttin stabilized the membrane expression of both zfclc‐k and rat ClC‐K.…”