Intriguing hemoglobin polymorphism in Grey Alpine cattle and functional effect

Genetic diversity is important for the maintenance of the viability and the evolutionary or adaptive potential of populations and species. The hemoglobin (Hb) represent a unique system for studying adaptive changes because these oxygen-carrying proteins closely connect metabolic activities with external conditions. As far as cattle are concerned, previous works evidenced an unusual hemoglobin polymorphism in Italian Podolic cattle; particularly, the HBAY variant was found to be associated with decreased hematocrit and hemoglobin values. In addition, the presence of identical marker alleles in Podolic cattle (Bos taurus) and Indian zebu (Bos indicus) provided further support for the theory that Asian bovine genes could have contributed in the past to the Podolic breed. Aim: Based on the above-mentioned evidences, the present paper has a double aim: (i) to check the presence of the above variants in breeds belonging to different cattle groups, namely, two undoubtedly Brachiceros breed - such as Italian Frisian (IF) and Italian Brow (IB) - and Grey Alpine (GA), a rustic cattle breed for which there are evidences suggesting resemblance with breeds classified as Bos taurus primigenius; (ii) to confirm the functional effect of the HBAY phenotype. Materials and Methods: In this study, a sample of 79 unrelated registered GA cattle was selected from a recently-established herd located in the province of Bari (Apulia, Italy) composed by animals purchased over time directly from different breeders from Northern Eastern Italy and thus quite representative of the original breeding area. For comparison, 82 unrelated registered IF cattle and 92 unrelated registered IB cattle were sampled in 10 different Apulian farms. Hematological variables were evaluated using a hematology analyzer. Hb phenotypes were analyzed with isoelectric focusing in a pH range of 6.7-7.7 (PAGIF). A T-test for independent samples was adopted to evaluate the significance of the difference in the mean hematocrit and hemoglobin values between the group of animals displaying and not displaying the Y alpha-globin variant. Results: The positively charged Y alpha-globin variant, encoded by the HBA1Y gene, was observed only in Grey Alpine with a 0.13 frequency value as opposed to that of the alternative N variant. We also recorded the presence of the common variants A and B of the beta globin system, along with the silent mutant AZebu, the frequency of the corresponding HBBA, HBBB and HBBAZebu genes being 0.73, 0.23 and 0.04, respectively. Neither HBA1Y alpha gene or AZebu beta allele was detected in the other sampled breeds. Conclusion: Actually, the presence of identical marker alleles in IP and GA suggests they share a common origin, possibly tracing back to earliest ancestors such as Bos primigenius primigenius. In addition, the present study provides further support for a functional effect of HBAY as associated with decreased hematocrit values in cattle