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This report is concerned with the evaluation of hematological parameters and of both relative (%) and absolute (mean pg/cell) quantities of the abnormal Hemoglobin (Hb) Hasharon in 53 heterozygous carriers and 7 double heterozygotes for Hb Hasharon and beta-thalassemia from 43 apparently unrelated families living in the province of Rovigo (northern Italy). Biosynthetic studies are also reported. The data strongly suggest the presence of an alpha-thalassemia-2 determinant closely linked to the alpha Hasharon-chain locus. Selective advantage of heterozygotes carrying such alpha-haplotype would explain the relatively high frequency of Hb Hasharon (0.23%) in northeastern Italy, a past-endemic malaria region. The interaction between Hb Hasharon and beta-thalassemia results in preferential decrease of the abnormal Hb level.

The allele frequencies for beta-thalassemia for 51 localities in the province of Rovigo, and in 25 localities in the province of Ferrara, were studied. It was observed that in the province of Ferrara there is a significant cline of frequencies; these decrease from the coast of the Adriatic Sea toward the west. No such gradient was visible in Rovigo. It was advanced, also on the basis of geography documented by ancient maps, that in the province of Rovigo there were multiple foci of selection for the thalassemia gene, and that in the province of Ferrara selection was stronger in the Oriental part of the area. Examination of the isolation by distance model with these data showed that the Malécot-Morton model fits for the Ferrara data and geography, whereas it does not for Rovigo.

The interactions between beta-thalassemia and the human hemoglobin (Hb) alpha-chain variants, Hb Hasharon, Hb O Idonesia and Hb J Paris, and between alpha-thalassemia and the beta-chain variants, Hb S, Hb C and Hb G San José, which are characterized by preferential decrease of the abnormal Hb level in peripheral bloods, have been studied. Both biosynthesis studies in reticulocytes and determination of the relative affinity of abnormal chains for normal complementary chains by in vivo recombination experiments, involving globin chains previously isolated in their native form, have been carried out in order to provide insights on the molecular events following the synthesis of the mutant chains under conditions of complementary chain deficiency. Furthermore, we have measured the relative affinity for complementary chain of beta D Los Angeles- and alpha J Rovigo-chains, the level of which does not decay in thalassemic carriers, and of alpha Legnano- and beta Osu Christiansborg-chains, which have not yet been observed in association with thalassemias. Our experiments indicated that the differential affinity for beta-chains is not always the major post-translational control mechanism which regulates the level of certain alpha-chain variants in beta-thalassemic heterozygotes, and that preferential removal of abnormal chains by proteolytic enzymes is likely to play an important role in most cases. On the other hand, the low affinity of certain variant beta-chains for alpha-chains may offer an explanation for the low level of certain beta-chain variants in peripheral blood of non-thalassemic carriers, as well as to their decrease under conditions of relative alpha-chain deficiency (alpha-thalassemias).

In subjects carrying the haemoglobin Hasharon mutation (alpha 47 replaced by His), originally from the delta of the Po river (Northern Italy), the concentration of the alpha-globin variant has been evaluated and found to be approximately 32%, a value definitely higher than that reported for the same mutant haemoglobin in other regions. Restriction enzyme analysis has been carried out on the DNA from these subjects; the data obtained indicate the presence of three alpha-globin genes per diploid cell. Family studies further show that the two normal genes are located on one chromosome and the Hasharon gene on the other. The origin of the single alpha-gene in the Hasharon-carrying subjects of the Ferrara region is discussed in connection with their haematological and biosynthetic data.