Model-Based Inference of Recombination Hotspots in a Highly, Variable Oncogene

Admixture mapping of tuberculosis and pigmentation-related traits in an African-European hybrid cattle population

Admixture mapping affords a powerful approach to genetic mapping of complex traits and may be particularly suited to investigation in cattle where many breeds and populations are hybrids of the two divergent ancestral genomes, derived from Bos taurus and Bos indicus. Here we design a minimal genome wide SNP panel for tracking ancestry in recent hybrids of Holstein–Friesian and local Arsi zebu in a field sample from a region of high bovine tuberculosis (BTB) endemicity in the central Ethiopian highlands. We first demonstrate the utility of this approach by mapping the red coat color phenotype, uncovering a highly significant peak over the MC1R gene and a second peak with no previously known candidate gene. Secondly, we exploit the described differential susceptibility to BTB between the ancestral strains to identify a region in which Bos taurus ancestry associates, at suggestive significance, with skin test positivity. Interestingly, this association peak contains the toll-like receptor gene cluster on chromosome 6. With this work we have shown the potential of admixture mapping in hybrid domestic animals with divergent ancestral genomes, a recurring condition in domesticated species.

Significance of variation within HIV, EBV, and KSHV subtypes

Since their initial transmission to humans, viruses have diversified extensively through recombination and mutation. The presence of intra- and inter-individual viral diversity influences disease progression, drug resistance, and therapy and presumably explains the conflicting results in many studies, including the failure of peptide-based vaccination strategies. Although HIV is a small RNA virus, coinfection with large DNA viruses, notably the oncogenic gamma-herpesviridae human herpesvirus-8 and Epstein Barr virus, is common. This coinfection occurs secondary to immunosuppression and shared transmission routes with high-risk predisposing behavior. In addition, all 3 of these viruses can lead to chronic infections, long periods of latency, and reactivation characterized by pain and suffering. The efficient targeting of their genetic diversity represents one of the major challenges in their control, both in prophylactic and therapeutic strategies. An understanding of diversity will help delineate whether population-specific vaccine strategies are necessary.

Nucleotide substitution at the highly polymorphic K1 locus of human herpesvirus 8 (Kaposi's sarcoma-associated herpesvirus)

The K1 locus is a highly polymorphic locus in the genome of human herpesvirus 8, the causative agent of Kaposi's sarcoma. Analysis of the pattern of nucleotide substitution among alleles at this locus supported the hypothesis that natural selection has acted to enhance amino acid diversity in the two hypervariable regions (VR1 and VR2) of the extracellular portion of the K1 protein. A phylogenetic analysis of 125 complete K1 sequences revealed two major clades, designated A/C and B. There was strong evidence against recombination between VR1 and VR2 among alleles belonging to different clades, and little support for frequent recombination within clades. The pattern of diversification of VR1 and VR2 within clades was similar to that between clades, but the immunoreceptor tyrosine-based activation motif (ITAM)-like sequence in the cytoplasmic region of K1 showed strong divergence between clades despite conservation within clades. The latter finding suggests that, while being subject to similar selection favoring diversity in the extracellular region, the two major clades of K1 alleles may be adapted for different types of interaction with host intracellular signal transduction mechanisms.