Alpha and beta globin polymorphism in Italian islander sheep breeds

Abstract

Previous investigations have highlighted the elevated haemoglobin polymorphism of Apulian native sheep. Thanks to the use of highly resolving analytical procedures (PAGIF, AUT-PAGE and RP-HPLC), the alpha globin genetic system (HBA) has been shown to exhibit both qualitative and quantitative variations (HBA1L, HBA1A, HBA1D, HBA2L, HBA2H, HBA3L, HBA3H, and HBA4H), while three allelic variants have been detected at the beta globin locus (HBBA, HBBB, and HBBI). The effect of a possibly adaptive response to the Apulian environmental conditions was suggested to account for both for the unusual presence of alpha haplotypes characterized by extra-numerary genes and the high frequency of the HBBB and HBBI alleles. Unfortunately, the few data in the literature regarding the HBA system polymorphism and the presence of the HBBI gene do not allow a comparison between Apulian sheep and those from other geographical areas. This work reports the results of a screening of Italian islander sheep breeds with a view to expanding the existing data set. A total of 465 blood samples were taken from 156 Comisana (C), 159 Sardinian (S) and 150 Valle del Belice (VdB) sheep belonging to 13 different flocks located in Apulia. Haemolysates were prepared from EDTA samples and analyzed by PAGIF, AUT-PAGE and RP-HPLC. Based on our results, the islander breeds exhibited slight differences in the HBA2H gene frequency compared to the HBA system of the Apulian native sheep; the most interesting finding was that though no HBA1D genes were recorded, the frequencies of triplicated haplotypes were very close, which supports the hypothesis that extra-numerary genes in Mediterranean environments may be an adaptive response to endemic tick borne parasites. Regarding the HBB locus, the results indicated that both Sicilian breeds exhibit an HBBI allele frequency of about 0.2, which is more than double that of previously reported data; this finding provided confirmatory evidence that HBBI is a rather common allele in Southern Italian sheep breed and suggested that an appropriate next step should be to investigate whether it presents the same frequency latitudinal cline as HBBB gene.