Springer Online Journal Archives 1860-2000
Summary Many cases of hereditary elliptocytosis (HE) result from mutated spectrin α-chains. It has repeatedly been observed that the amount of a mutant α-chain is different in various affected individuals, resulting in clinical pictures of variable severity. The different levels are thought to result from different percentages of the αspectrin allele in trans. Such percentages, in turn, could be under genetic control. We tested this hypothesis in a large Algerian family with SpαI/65 HE. In an informative sibship, we found three persons with a distinctly high level of expression of the SpαI/65 variant, suggesting the existence, in trans, of a low percentage α-allele. The α-spectrin gene haplotype associated with the latter was constantly − +−, based on the XbaI, PvuII and MspI polymorphic sites. In contrast, a basal level of expression of the SpαI/65 variant in the same sibship indicated, in trans, the existence of a normal percentage α-allele. The haplotype corresponding to this other α-allele was + − +. Study of another generation of the family showed, however, that the − + − haplotype could also be linked to a normal percentage α-allele. These results are consistent with the view that the expression level of αI/65 spectrin (and of other types of α-variants) is compounded by a genetic factor that is linked to the normal α-allele in trans. The low percentage allele itself remains silent in the simple heterozygous state.
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