Defining the Turkey MHC: Sequence and Genes of the B Locus

Abstract

The MHC, the most polymorphic and gene dense region in the vertebrate genome, contains many loci essential to immunity. In mammals, this region spans ∼4 Mb. Studies of avian species have found the MHC to be greatly reduced in size and gene content with an overall locus organization differing from that of mammals. The chicken MHC has been mapped to two distinct regions (MHC-B and -Y) of a single chromosome. MHC-B haplotypes possess tightly linked genes encoding the classical MHC molecules and few other disease resistance genes. Furthermore, chicken haplotypes possess a dominantly expressed class I and class II B locus that have a significant effect on the progression or regression of pathogenic disease. In this study, we present the MHC-B region of the turkey (Meleagris gallopavo) as a similarly constricted locus, with 34 genes identified within a 0.2-Mb region in near-perfect synteny with that of the chicken MHC-B. Notable differences between the two species are three BG and class II B loci in the turkey compared with one BG and two class II B loci in the chicken MHC-B. The relative size and high level of similarity of the turkey MHC in relation to that of the chicken suggest that similar associations with disease susceptibility and resistance may also be found in turkey.

No evidence for immunoproteasomes in chicken lymphoid organs and activated lymphocytes

“…BLAST search approaches in chicken, turkey, quail, black grouse, and zebra finch failed to detect genes for immuno-and thymoproteasome, suggesting that they have been lost in the lineage of birds (Balakrishnan et al 2010;Chaves et al 2009;Shiina et al 2007;Shiina et al 2004;Sutoh et al 2012;Wang et al 2012). While the genes coding for the catalytic subunits β1i and β5i are present in the class II region of the human and murine MHC loci, sequence searches in chicken genome databases revealed that there are no LMP genes in the avian MHC region, and also the immune subunit β2i could not be identified.…”

A locus-wide approach to assessing variation in the avian MHC: the B-locus of the wild turkey

“…Sequencing of the turkey B-locus (Chaves et al, 2009b) established the presence of three classical class IIB loci with at least two loci being expressed in the spleen. Goto et al (2002) described the use of single-strand conformation polymorphism for assaying MHC polymorphism in the chicken.…”

“…For consistency, the same PCR products used for DGGE were cloned using a pDrive Cloning Kit (Qiagen), transformed into DH5a cells (Invitrogen, Carlsbad, CA, USA), and over 20 purified plasmids were sequenced per individual. In addition, locus-specific primers (Chaves et al, 2009b) were used to individually sequence portions of the three known MHC-B class IIB genes from the single wild bird collected from Minnesota. Sequences of exon 2 were translated to identify putative PBR alleles.…”

“…Sequencing the MHC locus of the chicken, quail and turkey (MHC-B) identified the classical MHC class I and II genes within an B50 kb distance (Shiina et al, 2004(Shiina et al, , 2007Chaves et al, 2009b). Commercial selection has clearly reduced allelic diversity in chicken lines (Muir et al, 2008).…”

“…In the context of the MHC, the best-studied bird species are those of agricultural significance; MHC regions have been examined in chicken, quail, duck and turkey (Kaufman et al, 1999b;Moon et al, 2005;Shiina et al, 2004Shiina et al, , 2007Chaves et al, 2009bChaves et al, , 2011. Sequencing the MHC locus of the chicken, quail and turkey (MHC-B) identified the classical MHC class I and II genes within an B50 kb distance (Shiina et al, 2004(Shiina et al, , 2007Chaves et al, 2009b).…”