Abstract
The genes of the major histocompatibility complex
(MHC) are amongst the most variable in vertebrates
and represent some of the best candidates to study
processes of adaptive evolution. However, despite the
number of studies available, most of the information on
the structure and function of these genes come from studies
in mammals and birds in which the MHC class I and II
genes are tightly linked and class II alpha exhibits low
variability in many cases. Teleost fishes are among the most
primitive vertebrates with MHC and represent good
organisms for the study of MHC evolution because their
class I and class II loci are not physically linked, allowing
for independent evolution of both classes of genes. We have
compared the diversity and molecular mechanisms of
evolution of classical MH class II α and class II β loci in
farm populations of three salmonid species: Oncorhynchus
kisutch, Oncorhynchus mykiss and Salmo salar. We found
single classical class II loci and high polymorphism at both
class II α and β genes in the three species. Mechanisms of
evolution were common for both class II genes, with
recombination and point mutation involved in generating
diversity and positive selection acting on the peptidebinding
residues. These results suggest that the maintenance
of variability at the class IIα gene could be a
mechanism to increase diversity in the MHC class II in
salmonids in order to compensate for the expression of one
single classical locus and to respond to a wider array of
parasites.
Original language | English |
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Pages (from-to) | 531-542 |
Number of pages | 12 |
Journal | Immunogenetics |
Volume | 62 |
Issue number | 8 |
DOIs | |
Publication status | Published - 01 Aug 2010 |
Keywords
- MHC class II
- Adaptive evolution
- Oncorhynchus mykiss
- Oncorhynchus kisutch
- Salmo salar