BAND-3 CAMPINAS - A NOVEL SPLICING MUTATION IN THE BAND-3 GENE (AE1) ASSOCIATED WITH HEREDITARY SPHEROCYTOSIS, HYPERACTIVITY OF NA+ LI+ COUNTERTRANSPORT AND AN ABNORMAL RENAL BICARBONATE HANDLING/

We have studied the molecular defect underlying band 3 deficiency in o ne family with hereditary spherocytosis using nonradioactive single st rand conformation polimorphism of polymerase chain reaction (PCR) ampl ified genomic DNA of the AET gene, By direct sequencing, a single base substitution in the splicing donor site of intron 8 (position + 1G -- > T) was identified, The study of the cDNA showed a skipping of exon 8 , This exon skipping event is responsible for a frameshift leading to a premature stop codon 13 amino acids downstream. The distal urinary a cidification test by furosemide was performed to verify the consequenc es of the band 3 deficiency in cu intercalated cortical collecting duc t cells (alpha ICCDC), We found an increased basal urinary bicarbonate excretion, associated with an increased basal urinary pH and an effic ient distal urinary acidification, We also tested the consequences of band 3 deficiency on the Na+/H+ exchanger, by the measurement of Na+/L i+ countertransport activity in red blood cells. The Na+/Li+ countertr ansport activity was increased threefold to sixfold in the patients co mpared with the controls. It is possible that band 3 deficiency in the kidney leads to a decrease in the reabsorption of HCO3- in alpha ICCD C and anion loss, which might be associated with an increased sodium-l ithium countertransport activity. (C) 1997 by The American Society of Hematology.