β-spectrinBari: a truncated β-chain responsible for dominant hereditary spherocytosis

We describe a beta-spectrin variant, named beta-spectrin Bari, characterized by a truncated chain and associated with hereditary spherocytosis. The clinical phenotype consists of a moderately severe hemolytic anemia, splenomegaly, and spherocytes and acanthocytes in the blood smear. The occurrence of the truncated protein, that represents about 8% of the total beta-spectrin occurring on the membrane, results in a marked spectrin deficiency. The altered protein is due to a single point mutation at position -2 (A -> G) of the acceptor splice site of intron 16 leading to an aberrant beta-spectrin message skipping exons 16 and 17 indistinguishable from that reported for beta-spectrin Winston-Salem. We provide evidence that the mutated gene is transcribed but its mRNA is less abundant than either its normal counterpart or beta-spectrin Winston-Salem mRNA. Our findings are an example of how mutations in different splice sites, although causing the same truncating effect, result in clearly different clinical pictures.