High-resolution melting analysis of common and recombinant genotypes of the Atlantic cod (Gadus morhua) hemoglobin β1 gene in transatlantic populations

Abstract

High-resolution melting (HRM) analysis was applied to haplotype the Met55Val–Lys62Ala mutations of the Atlantic cod ( Gadus morhua ) Hb-β1 gene responsible for the important hemoglobin polymorphisms. The Val55–Ala62 haplotype predominated in cod populations throughout the Northwest Atlantic Ocean and the northern Norwegian and Baltic seas, while the Met55–Lys62 variant was mostly found in the North Sea, Kattegat, and along the southern part of the Norwegian coast. Whereas the distribution of the two main haplotypes show a temperature-related north–south gradient in Northeast Atlantic populations, this study provided no evidence for such a cline on the western side of the North Atlantic Ocean. Coupling and repulsion double heterozygotes were readily distinguished by the HRM assay, but no repulsion heterozygote specimens were found on either side of the Atlantic Ocean. The recombinant haplotype Val55–Lys62 was detected in variable numbers in both Northwest and Northeast Atlantic populations, with the highest frequencies in the Canadian populations. The reciprocal Met55–Ala62 recombination was almost absent in the populations examined and probably represents a disadvantage, particularly at elevated temperatures. Our HRM assay affords low-cost, precise, and efficient Hb-β1 polymorphism haplotyping in large numbers of DNA samples in small, moderately equipped laboratories.