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A variant of the EPB3 gene of the anti‐Lepore type in hereditary spherocytosis
Author(s) -
Bianchi Paola,
Zanella Alberto,
Alloisio Nicole,
Barosi Giovanni,
Bredi Elena,
Pelissero Giovanni,
Zappa Manuela,
Vercellati Cristina,
Baronciani Luciano,
Delaunay Jean,
Sirchia Girolamo
Publication year - 1997
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1046/j.1365-2141.1997.1983013.x
Subject(s) - hereditary spherocytosis , gene duplication , band 3 , exon , genetics , gene , biology , microbiology and biotechnology , intron , tandem exon duplication , membrane protein , membrane
The EPB3 gene encodes band 3 (anion exchanger 1) of the red cell membrane. A subset of hereditary spherocytosis (HS) is associated with EPB3 gene mutations and band 3 deficiency. We report a large Italian family in which 10 of the 27 members investigated displayed an autosomal dominant HS. SDS‐PAGE revealed a reduction in band 3 in the patients. Screening of the Pst I polymorphic site confirmed the linkage of HS with the EPB3 gene. Analysis of complementary and genomic DNA showed a large additional segment. Nucleotide sequencing disclosed an in‐frame duplication of 69 nucleotides (nt) including a triplet of intronic origin and a genuine exonic duplication of 66 nt. Two CCTGC sequences occurred close to one another, one near the intron 12 acceptor splice site (nt −7 to −3), and the other within exon 13 (nt 1494–1498). We assumed that the abnormal allele arose from an unequal recombination event of the anti‐Lepore type between the two CCTGC sequences. At the level of the mutated protein, termed band 3 Milano, the additional segment (Gln plus duplication of residues 478–499) corresponded to the last part of the third transmembrane domain (TM3), the entire second outer loop and part of TM4 as it is currently defined in hydropathy analysis. After deglycosylation of band 3, only the normal band was detected, supporting the view that band 3 Milano is probably not incorporated into the membrane.