Spectrin Tunis (αI/78): A New αI Variant That Causes Asymptomatic Hereditary Elliptocytosis in the Heterozygous State

Spectrin Tunis (α1/78) was found in the heterozygous state in a young white North-African man and his mother. Both of them presented with mild elliptocytosis. Using one-dimensional electrophoresis, a sharp 78 kd fragment was present with a reciprocal decrease of the al 80 kd domain. Kinetic analysis unambiguously confirmed that the 78 kd fragment developed at the expense of the al 80 domain. The al 74 kd peptide was not flanked with a peptide lacking a 2 kd fragment. From this fact, it could be inferred that the site for additional proteolysis is located upstream from arginyl residue 39 and, more precisely, should lie 10 to 20 amino-acid residues ( — 2 kd) from the a-chain N-terminus. The percentage of spectrin dimers in 4°C extracts was high (over 40%), contrasting with the absence of clinical symptoms related to elliptocytosis. This is the first mutation responsible for elliptocytosis found in Tunisia.1988 by Grune & Stratton, Inc. 0006-4971/88/7102-0152$3.00/0