Inherited Distal Renal Tubular Acidosis

A Novel Missense Mutation in AE1 Causing Autosomal Dominant Distal Renal Tubular Acidosis Retains Normal Transport Function but Is Mistargeted in Polarized Epithelial Cells

“…As expected, this revealed similar results to the 36 Cl Ϫ influx study. The calculated HCO 3 Ϫ efflux induced by oocytes injected with wild-type or mutant kAE1 cRNA was 15.5 and 16.4 nmol of HCO 3 Ϫ /oocyte/h, respectively. Taken together, these experiments demonstrate that this kAE1 mutant protein retains normal anion (Cl Ϫ /HCO 3 Ϫ ) transport activity.…”

“…Initially oocytes were incubated in a chloride-free gluconate/HCO 3 Ϫ solution (96 mM sodium gluconate, 2 mM potassium gluconate, 1 mM MgSO 4 , 10 mM NaHCO 3 ) for 1 h at 19°C. This medium was removed and replaced with 250 l of ND96/HCO 3 Ϫ solution (96 mM NaCl, 2 mM KCl, 1.8 mM CaCl 2 , 1 mM CaCl 2 , 10 mM NaHCO 3 ).…”

“…100-l samples were taken at time 0 and again after 1 h. Samples were equilibriated with 95% O 2 , 5% CO 2 , and the pH of the medium was read using a micro pH electrode (Hanna HI 1083, Jencons-PLS). The HCO 3 Ϫ flux/oocyte is given by the equation…”

“…The Since kAE1 functions as a one-to-one Cl Ϫ -HCO 3 Ϫ exchanger (28) across the basolateral membrane of ␣-intercalated cells, we wanted to confirm this function of the mutant protein by assaying HCO 3 Ϫ efflux. Although HCO 3 Ϫ efflux could not be measured from single oocytes, we developed a method to determine its efflux from batches of 30 -40 injected oocytes.…”

“…This disorder is usually accompanied by hypokalemia, metabolic bone disease, nephrocalcinosis, and/or nephrolithiasis (1)(2)(3). Mutations in SLC4A1 (MIM 109270), encoding the polytopic chloride-bicarbonate exchanger known as AE1, have been reported as the sole genetic cause of autosomal dominant dRTA (ddRTA) (MIM #179800) (4 -9) and also rarely cause autosomal recessive dRTA (10 -14).…”