Interaction Between Hb Hasharon and a-Thalassemia: An Approach to the Problem of the Number ofHuman a Loci

We report the case of an Italian infant girl hand, in the Askenazy carriers of Hb Ha-from Polesine (Po delta region in northern sharon, Hb Hasharon is probably linked to Italy) who was heterozygous for Hb Ha- a normal a gene. In comparing Hb Ha-sharon and a-thalassemia, did not synthe- sharon’s behavior with that of other a size any normal HbA, and had 3 % HbH on variants, particularly HbG Philadelphia, electrophoresis. Hematologic and biosyn- frequent recombinations between a struc-thetic studies on Hb Hasharon carriers of tural genes were suggested. The possible the propositus ’ family suggest the possibil- identity between the single a locus and ity that the Hb Hasharon gene is linked to the a2-thalassemia genotype is dis-an a-thalassemia gene. On the other cussed. T DIFFERENT MODELS have been proposed for the number of structural a loci-one with two and the other with a single locus. The finding of a subject carrying two different a mutants, HbJ Buda and HbG Pest, ’ who also had about 50 % normal HbA, supports the two a loci hy-pothesis, at least in part of the human population. On the other hand, homo-zygotes for HbJ Tongariki2’3 do not synthesize any normal a chain. This fact agrees with the single-locus hypothesis, even if the duplication of the HbJ Tongariki gene or its linkage with an a-thalassemia gene cannot be excluded. However, the hematologic picture of these subjects is not consistent with a-thalassemia. Further data have been provided by studies of some heterozygotes for a-thalassemia and an a variant who did not synthesize any HbA.47 These cases suggest that these a mutants exist in a genetic pattern without a normal a gene in cis. Therefore they are either single-locus mutants or are linked to an a-thalassemia gene. In this paper we describe a family in which a subject synthesizes only a Hasharon chains and the heterozygous carriers of Hb Hasharon show dif-ferent percentages of the abnormal hemoglobin. Our data, compared with those reported in the literature, permit some comments about the a loci pat-tern in the Italian population of Polesine (Po delta region in northern Italy)