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
Paulo R.M. Lima,
José A.R. Gontijo,
José B. Lopes de Faria,
Fernando F. Costa, and
Sara T.O. Saad
From Hemocentro, Departamento de Clínica Médica, Faculdade de Ciências Médicas, Campinas, São Paulo; and Departamento de Bioquímica, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Campinas, São Paulo, Brazil.
We have studied the molecular defect underlying band 3 deficiency in one family with hereditary spherocytosis using nonradioactive single strand conformation polimorphism of polymerase chain reaction (PCR) amplified genomic DNA of the AE1 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 acidification test by furosemide was performed to verify the consequences of the band 3 deficiency in 
intercalated cortical collecting duct cells (ICCDC). We found an increased basal urinary bicarbonate excretion, associated with an increased basal urinary pH and an efficient distal urinary acidification. We also tested the consequences of band 3 deficiency on the Na+/H+ exchanger, by the measurement of Na+/Li+ countertransport activity in red blood cells. The Na+/Li+ countertransport activity was increased threefold to sixfold in the patients compared with the controls. It is possible that band 3 deficiency in the kidney leads to a decrease in the reabsorption of HCO-3 in ICCDC and anion loss, which might be associated with an increased sodium-lithium countertransport activity.
Blood, Vol. 90 No. 7 (October 1), 1997:
pp. 2810-2818
© 1997 by The American Society of Hematology.
