The current information on the polymorphism variation and haplotype structure of the domestic dog leukocyte antigen (DLA) genes is limited in comparison to other experimental animals. In this paper, to better elucidate the degree and types of polymorphisms and genetic differences for DLA-88, DLA-12 and DLA-64, we genotyped four families of 38 beagles and another 404 unrelated dogs representing 49 breeds by RT-PCR based Sanger sequencing. We also sequenced and analyzed the genomic organization of the DLA-88 and DLA-12 gene segments to better define these two-gene DLA haplotypes more precisely. We identified 45 alleles for DLA-88, 15 for DLA-12 and six for DLA-64, of which 20, 14 and six, respectively, were newly described alleles. Therefore, this study shows that the DLA-12 and DLA-64 loci are far more polymorphic than previously reported. Phylogenetic analysis strongly supported that the DLA-88, DLA-12 and DLA-64 alleles were independently generated after the original divergence of the DLA-79 alleles. Two distinct DLA-88 and DLA-12 haplotype structures, tentatively named DLA-88-DLA-12 and DLA-88-DLA-88L, were identified, and the novel haplotype DLA-88-DLA-88L contributed to 32.7% of the unrelated dogs. Quantitative real-time PCR analysis showed that the gene expression levels of DLA-88L and DLA-88 were similar, and that the gene expression level of DLA-12 was significantly lower. In addition, haplotype frequency estimations using frequently occurring alleles revealed 45 different DLA-class I haplotypes (88-88L/12-64) overall, and 22 different DLA-class I haplotypes in homozygous dogs for 18 breeds and mongrels.

The major histocompatibility complex (MHC) is a highly polymorphic and duplicated genomic region that encodes transplantation and immune regulatory molecules. Although it is well-known that particular MHC allelic polymorphisms and haplotypes are genetically relate to immune-mediated diseases detailed information of the cat MHC (Feline Leukocyte Antigen; FLA) genetic and haplotypic structure and diversity is limited in comparison to humans and many other species. In this study, to better understand the degree and types of allele and allelic haplotype diversity of FLA-class I (FLA-I) and FLA-DRB loci in domestic cats, we identified six expressible FLA-I loci in peripheral white blood cells by in silico estimation of the coding exons and NGSbased amplicon sequencing using five unrelated cats. We then used a newly developed NGS-based genotyping method to genotype and annotate 32 FLA-I and 16 FLA-DRB sequences in two families of 20 domestic cats. A total of 14 FLA-I and seven FLA-DRB were identified as novel polymorphic sequences. Phylogenetic analyses grouped the sequences into six FLA-I (FLA-E/H/K, FLA-A, FLA-J, FLA-L, FLA-O and a tentatively named FLA-E/H/K_Rec) and four FLA-DRB (FLA-DRB1, FLA-DRB3, FLA-DRB4, and FLA-DRB5) lineages. Pedigree analysis of two cat families revealed eight distinct FLA structural haplotypes (Class I-DRB) with five to eight FLA-I and two to three FLA-DRB transcribed loci per haplotype. It is evident that the eight FLA haplotypes were generated by gene duplications and deletions, and rearrangements by genetic recombination with the accumulation and/or inheritance of novel polymorphisms. These findings are useful for further genetic diversity analysis and disease association studies among cat breeds and in veterinary medicine.

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