Spectrin beta Tandil, a novel shortened beta-chain variant associated with
hereditary elliptocytosis is due to a deletional frameshift mutation in the
beta-spectrin gene
M Garbarz, L Boulanger, S Pedroni, MC Lecomte, H Gautero, C Galand, P Boivin, L Feldman and D Dhermy
INSERM U160, Hopital Beaujon, Clichy, France.
An Argentinian family with hereditary elliptocytosis (HE) associated with a
shortened beta-spectrin (Sp) chain was studied. As with most of the other
shortened Sp beta-chains that have been described, this variant, called
SpTandil, has impaired ability to participate in Sp dimer self-association,
has lost its ability to become phosphorylated, and is associated with the
presence of increased amounts of the alpha I 74-Kd fragment after partial
tryptic digestion of Sp. The 3' ends of the beta-Sp gene of affected
patients were analyzed. cDNA was prepared by reverse transcription of
peripheral blood mRNA and amplified by the polymerase chain reaction (PCR)
using primers corresponding to sequences 400 bp apart on the cDNA, spanning
the last three exons (X, Y, Z) of the beta-Sp gene. Agarose gel
electrophoresis of the cDNA amplification showed the presence of one band,
the size of which was apparently the same as the band amplified from mRNA
of a normal control. cDNA from one HE patient was subcloned and sequenced.
Several clones showed the presence of a 7-bp deletion at codon 2041 in exon
X. Genomic DNA of all the affected members of the family were amplified by
PCR using primers flanking the deletion and corresponding to sequences 128
bp apart on exon X. Analysis of the PCR products using electrophoresis on
polyacrylamide gel showed the presence of 121- and 128-bp bands in all HE
subjects, and an additional doublet migrating more slowly than the two
bands, which corresponded to the presence of heteroduplexes. The mutation
results in a shift of the normal reading frame and leads to a new amino
acid sequence at the C-terminus of the mutant beta-Sp chain. A new in-frame
stop codon is encountered downstream, leading to premature chain
termination. The identification of the molecular defect in Sp beta Tandil
provides information regarding the region of the beta-Sp chain that is
important for both Sp dimer self-association and an indication of potential
sites of phosphorylation of the chain.
Volume 80,
Issue 4,
pp. 1066-1073,
08/15/1992
Copyright © 1992 by The American Society of Hematology
