Incomplete Distal Renal Tubular Acidosis from a Heterozygous Mutation of the V-ATPase B1 Subunit

Zhang, Jianning; Fuster, Daniel Guido; Cameron, Mary Ann; Quinones, Herny; Griffith, Carolyn; Xie, Xiao-Song; Moe, Orson W. (2014). Incomplete Distal Renal Tubular Acidosis from a Heterozygous Mutation of the V-ATPase B1 Subunit. American journal of physiology - renal physiology, 307(9), F1063-F1071. American Physiological Society 10.1152/ajprenal.00408.2014

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Congenital distal renal tubular acidosis (dRTA) from mutations of the B1 subunit of the V-ATPase is considered an autosomal recessive disease. We analyzed a dRTA kindred with a truncation-mutation of B1 (p.Phe468fsX487) previously shown to have failure of assembly into the V1 domain of the V-ATPase. All heterozygous carriers in this kindred have normal plasma bicarbonate concentrations, thus evaded the diagnosis of RTA. However, inappropriately high urine pH, hypocitraturia, and hypercalciuria are present either individually or in combination in the heterozygotes at baseline. Two of the heterozygotes studied also have inappropriate urinary acidification with acute ammonium chloride loading and impaired urine-blood pCO2 gradient during bicarbonaturia indicating presence of H+ gradient and flux defects. In normal human renal papillae, wild type B1 is located primarily on the plasma membrane but papilla from one of the heterozygote who had kidney stones had renal tissue secured from surgery showed B1 in both plasma membrane as well as a diffuse intracellular staining. Titrating increasing amounts of the mutant B1 subunit did not exhibit negative dominance over the expression, cellular distribution, or H+-pump activity of the wild type B1 in mammalian HEK293 cells and in V-ATPase-deficient S. cerevisiae. This is the first demonstration of renal acidification defects and nephrolithiasis in heterozygous carriers of mutant B1 subunit; which cannot be attributable to negative dominance. We propose that heterozygosity may lead to mild real acidification defects due to haploinsufficiency. B1 heterozygosity should be considered in patients with calcium nephrolithiasis and urinary abnormalities such as alkalinuria or hypocitraturia.

Item Type:

Journal Article (Original Article)

Division/Institute:

04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Biochemistry and Molecular Medicine
04 Faculty of Medicine > Pre-clinic Human Medicine > BioMedical Research (DBMR) > Unit Childrens Hospital > Forschungsgruppe Nephrologie / Hypertonie
04 Faculty of Medicine > Department of Dermatology, Urology, Rheumatology, Nephrology, Osteoporosis (DURN) > Clinic of Nephrology and Hypertension

Graduate School:

Graduate School for Cellular and Biomedical Sciences (GCB)

UniBE Contributor:

Fuster, Daniel Guido

Subjects:

500 Science > 570 Life sciences; biology
600 Technology > 610 Medicine & health

ISSN:

0363-6127

Publisher:

American Physiological Society

Language:

English

Submitter:

Daniel Guido Fuster

Date Deposited:

09 Oct 2014 11:51

Last Modified:

16 Jul 2018 12:38

Publisher DOI:

10.1152/ajprenal.00408.2014

PubMed ID:

25164082

BORIS DOI:

10.7892/boris.58698

URI:

https://boris.unibe.ch/id/eprint/58698

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