Variability of major histocompatibility complex DQA and DQB class II genes in the striped dolphin (Stenella coeruleoalba) and Risso's dolphin (Grampus griseus)

Abstract

Glavni sustav tkivne podudarnosti (MHC) ima središnju imunoregulacijsku ulogu. Raznolikost MHC-a je bitna za preživljavanje vrste jer omogućava prepoznavanje širokog spektra patogena. Ta raznolikost je nastala pod utjecajem selekcije, pa MHC geni služe kao biljezi za proučavanje adaptivne evolucije populacija i vrsta. Plavobijeli dupin (Stenella coeruleoalba) i glavati dupin (Grampus griseus) pripadaju porodici Delphinidae, podred Odontoceti, red Cetacea. Obje vrste nastanjuju topla i umjereno topla mora i to uglavnom pučinske dijelove. Cilj istraživanja bio je odrediti razinu raznolikosti gena DQA i DQB skupine II MHC sustava plavobijelog i glavatog dupina. U uzorcima tkiva 24 jedinke plavobijelog i osam jedinki glavatog dupina iz Sredozemnog mora pronađen je ukupno 21 alel na DQA lokusu i 21 alel na DQB lokusu, od kojih su samo tri DQA alela poznata iz prethodnih istraživanja. Broj jedinstvenih alela, kao i evolucijske udaljenosti ukazuju na visok stupanj raznolikosti u obje vrste, dok omjer stopa nesinonimnih i sinonimnih supstitucija potvrđuje pretpostavku da je raznolikost na istraživanim lokusima održavana pozitivnom selekcijom.Major histocompatibility system (MHC) has a central role in the regulation of immune response. MHC diversity is essential for the survival of the species because it allows for the recognition of a wide spectrum of pathogens. That diversity evolved under selective pressure, so MHC genes can be used as markers for the study of adaptive evolution in populations or species. Striped dolphin (Stenella coeruleoalba) and Risso’s dolphin (Grampus griseus) are a part of the family Delphinidae, suborder Odontoceti, order Cetacea. Both species inhabit pelagic warm and temperate waters. The goal of this study was to determine the variability of MHC class II DQA and DQB genes in the striped dolphin and Risso’s dolphin. In tissue samples from 21 striped and eight Risso’s dolphins a total of 21 DQA and 21 DQB alleles were found, of which only three DQA alleles were known from previous studies. The number of unique alleles, as well as the calculated evolutionary distances show a high level of diversity in both species, while the rates of non-synonymous and synonymous substitutions indicate the maintenance of the diversity on both loci by positive selection