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Peptide-specific natural killer cell receptors.
Class I and II human leukocyte antigens (HLA-I and HLA-II) present peptide antigens for immunosurveillance by T cells. HLA molecules also form ligands for a plethora of innate, germline-encoded receptors. Many of these receptors engage HLA molecules in a peptide sequence independent manner, with binding sites outside the peptide binding groove. However, some receptors, typically expressed on natural killer (NK) cells, engage the HLA presented peptide directly. Remarkably, some of these receptors display exquisite specificity for peptide sequences, with the capacity to detect sequences conserved in pathogens. Here, we review evidence for peptide-specific NK cell receptors (PSNKRs) and discuss their potential roles in immunity.
Conservation genomics of urban populations of Streamside Salamander (Ambystoma barbouri).
In Tennessee, populations of the state endangered Streamside Salamander (Ambystoma barbouri) are in decline as their distribution lies mostly within rapidly developing areas in the Nashville Basin. Information regarding the partitioning of genetic variation among populations of A. barbouri and the taxonomic status of these populations relative to northern populations and their congener, the Small-mouthed Salamander (A. texanum), have important implications for management and conservation of this species. Here we combined mitochondrial sequencing and genome-wide single nucleotide polymorphism (SNP) data generated using Genotyping-by-Sequencing (GBS) to investigate patterns of genetic variation within Tennessee populations of A. barbouri, to assess their relationship to populations in Kentucky, and to examine their phylogenetic relationship to the closely related A. texanum. Results from phylogenetic reconstructions reveal a complex history of Tennessee A. barbouri populations with regards to northern populations, unisexual A. barbouri, and A. texanum. Patterns of mitochondrial sequence variation suggest that A. barbouri may have originated within Tennessee and expanded north multiple times into Kentucky, Ohio, Indiana, and West Virginia. Phylogenetic reconstructions based on genome-wide SNP data contradict results based on mitochondrial DNA and correspond to geographic and taxonomic boundaries. Variation in allele frequencies at SNP genotypes, as identified by multivariate analyses and Bayesian assignment tests, identified three evolutionary significant units (ESUs) for A. barbouri within Tennessee. Collectively, these results emphasize the need for prioritizing conservation needs for Tennessee populations of A. barbouri to ensure the long-term persistence of this species.