CHARACTERIZATION OF 13 NOVEL BAND-3 GENE DEFECTS IN HEREDITARY SPHEROCYTOSIS WITH BAND-3 DEFICIENCY

Hereditary spherocytosis (HS) is a common hemolytic anemia of variable clinical expression. Pathogenesis of HS has been associated with defe cts of several red cell membrane proteins including erythroid band 3. We have studied erythrocyte membrane proteins in 166 families with aut osomal dominant HS. We have detected relative deficiency of band 3 in 38 kindred (23%). Band 3 deficiency was invariably associated with mil d autosomal dominant spherocytosis and with the presence of pincered r ed cells in the peripheral blood smears of unsplenectomized patients. We hypothesized that this phenotype is caused by band 3 gene defects. Therefore, we screened band 3 DNA from these 38 kindred for single str and conformational polymorphisms (SSCP). In addition to five mutations detected previously by SSCP screening of cDNA, we detected 13 new ban d 3 gene mutations in 14 kindred coinherited with HS. These novel muta tions consisted of two distinct subsets. The first subset included sev en nonsense and frameshift mutations that were all associated with the absence of the mutant mRNA allele from reticulocyte RNA, implicating decreased production and/or stability of mutant mRNA as the cause of d ecreased band 3 synthesis. The second group included five substitution s of highly conserved amino acids and one in-frame deletion. These six mutations were associated with the presence of comparable levels of n ormal and mutant band 3 mRNA. We suggest that these mutations interfer e with band 3 biosynthesis leading thus to the decreased accumulation of the mutant band 3 allele in the plasma membrane. (C) 1996 by The Am erican Society of Hematology.