Simultaneous fine mapping of closely linked epistatic quantitative trait loci using combined linkage disequilibrium and linkage with a general pedigree

Causal mutations and their intra- and inter-locus interactions play a critical role in complex trait variation. It is often not easy to detect epistatic quantitative trait loci (QTL) due to complicated population structure requirements for detecting epistatic effects in linkage analysis studies and due to main effects often being hidden by interaction effects. Mapping their positions is even harder when they are closely linked. The data structure requirement may be overcome when information on linkage disequilibrium is used. We present an approach using a mixed linear model nested in an empirical Bayesian approach, which simultaneously takes into account additive, dominance and epistatic effects due to multiple QTL. The covariance structure used in the mixed linear model is based on combined linkage disequilibrium and linkage information. In a simulation study where there are complex epistatic interactions between QTL, it is possible to simultaneously map interacting QTL into a small region using the proposed approach. The estimated variance components are accurate and less biased with the proposed approach compared with traditional models.     

Single-queen introductions characterize regional and local invasions by the facultatively clonal little fire ant Wasmannia auropunctata

Clonal reproduction may facilitate the spread of invasive species by reducing the minimum population size necessary for successful establishment. We used microsatellite markers to reconstruct the composition of founding populations in two regional (Central Africa and Hawaii) and 23 local (near a Gabonese oilfield) invasions of the facultatively parthenogenetic little fire ant. Central Africa had a single dominant queen clone, which appears to have initiated the regional infestation, and then produced numerous other clones by rare sexual reproduction. This interpretation of the data was also supported by the genotype of a worker from the first collection in Africa (Gabon 1913). We found only a single queen clone in Hawaii, likewise indicating a single-clone introduction, most likely from an earlier infestation in Florida. Single-clone introductions also gave rise to the vast majority (92%) of local infestations at our oilfield study site. These results suggest the unusual, largely clonal, reproductive strategy of the little fire ant may enhance its success as an invasive species. However, the occasional sexual production of novel genotypes after the initial introduction may provide genetic flexibility that overcomes shortcomings of pure clonality.     

AH jump duration is associated with elimination of slow pathway during ablation of atrioventricular nodal reentrant tachycardia

IntroductionAblating the slow pathway (SP) is the superior treatment for atrioventricular nodal reentrant tachycardia (AVNRT) with a low complication rate. However, the ablation of the SP could result in either complete elimination or modification of the SP. We aimed to investigate whether the duration of AH jump pre-ablation associated with the outcome of elimination of SP.MethodsWe included 56 patients with typical AVNRT (slow-fast), 20 males and 36 females, aged 44.2 ± 15.1 years. Slow pathway ablation was performed using classical approach. Univariate and multivariate analysis was performed for potential predictors of SP elimination.ResultsTypical AVNRT was inducible in all patients. Post-ablation, non-inducibility of AVNRT was obtained in all 56 (100%) patients, with SP elimination in 33 (61%) patients and SP modification in 23 (39%) patients. Patients with SP elimination had significantly longer AH jump than patients with SP modification. Cox regression analysis showed that AH jump duration was the independent predictor of SP elimination, in which every 20 ms increase in AH jump duration was associated with 1.30 higher rate of SP elimination. Furthermore, ROC curve analysis indicated that the AH jump duration of ≥100 ms had 6.14 times higher probability for complete elimination of the SP with a sensitivity of 79%, specificity of 70%, PPV of 79% and NPV of 70%.ConclusionsAH jump duration pre-ablation is associated with complete elimination of slow pathway during AVNRT ablation.