Loss of kAE1 expression in collecting ducts of end-stage kidneys from a family with SLC4A1 G609R-associated distal renal tubular acidosis.

Distal renal tubular acidosis caused by missense mutations in kidney isoform of anion exchanger 1 (kAE1/SLC4A1), the basolateral membrane Cl(-)/HCO3(-) exchanger of renal alpha-intercalated cells, has been extensively investigated in heterologous expression systems but rarely in human kidneys. The preferential apical localization of distal renal tubular acidosis (dRTA)-associated kAE1 mutants R901X, G609R and M909T in cultured epithelial monolayers has not been examined in human kidney. Here, we present kidney tissues from dRTA-affected siblings heterozygous for kAE1 G609R, characterized by predominant absence rather than mistargeting of kAE1 in intercalated cells. Thus, studies of heterologous recombinant expression of mutant proteins should be, whenever possible, interpreted in comparison to affected patient tissues.