Association between genetic risk score and periodontitis onset and progression: a pilot study.

AIM: Recent research has focused attention on the single nucleotide polymorphisms (SNPs) involved in the host response in periodontitis. However, so as to combine the relatively small effects of individual genes the use of multi locus genetic risk (GRS) has been proposed. This study aims to evaluate whether the genetic risk score may predict periodontitis onset and progression. MATERIALS AND METHODS: Fifty patients were divided into various groups according to periodontal status. Total DNA was isolated from epithelial oral cells by a masked operator and the selected SNPs were analysed. A GRS was calculated using an additive model. RESULTS: We found a strong association only between TNF rs1800629 and diffused forms of periodontitis. Data show that GRS is able to discriminate diffused forms of periodontitis from localized ones. Finally, a progressive increase of the GRS is evident in advanced periodontitis in comparison with early forms. DISCUSSION: In recent years, research on genetic polymorphism has had limited success in predicting the susceptibility to periodontal disease. However, our results indicate that the use of the genetic risk score could be promising. Further studies are necessary to include data from multiple genes so as to confirm our result.

Characterization of microsatellite loci in the subsocial spider Stegodyphus lineatus (Araneae: Eresidae).

Stegodyphus lineatus spiders live in groups consisting of closely related individuals. There appears to be no discrimination against related individuals as mates but females mate multiply, despite the fact that matings are shown to carry a cost. We have developed eight polymorphic dinucleotide microsatellite markers that allow us to assess levels of heterozygosity and relatedness among individuals of this species. These molecular markers are likely to prove highly effective tools for estimating levels of inbreeding and thus allow us to test hypotheses about the relationships between social structure, mating strategies and inbreeding avoidance.

Phylogeography of the rock partridge (Alectoris graeca).

We used mitochondrial DNA control-region and microsatellite data to infer the evolutionary history and past demographic changes in 332 rock partridges (Alectoris graeca) sampled from throughout the species' distribution range, with the exception of the central Balkans region. Maternal and biparental DNA markers indicated concordantly that rock partridge populations are structured geographically (mtDNA phiST = 0.86, microsatellite FST = 0.35; RST = 0.31; P < 0.001). Phylogenetic analyses of 22 mtDNA haplotypes identified two major phylogroups (supported by bootstrap values = 93%), splitting partridges from Sicily vs. all the other sampled populations at an average Tamura-Nei genetic distance of 0.035, which corresponds to 65% of the average distance between closely related species of Alectoris. Coalescent estimates of divergence times suggested that rock partridges in Sicily were isolated for more than 200000 years. This deep subdivision was confirmed by multivariate, Bayesian clustering and population assignment analyses of microsatellite genotypes, which supported also a subdivision of partridges from the Alps vs. populations in the Apennines, Albania and Greece. Partridges in the Apennines and Albania-Greece were probably connected by gene flow since recently through a late Pleistocene Adriatic landbridge. Deglaciated Alps were probably colonized by distinct and, perhaps, not yet sampled source populations. Bottleneck and mismatch analyses indicate that rock partridges have lost variability through past population declines, and did not expand recently. Deglaciated areas could have been recolonized without any strong demographic expansion. Genetic data partially supported subspecies subdivisions, and allowed delimiting distinct conservation units. Rock partridges in Sicily, formally recognized as A. g. whitakeri, met the criteria for a distinct evolutionary significant unit.

Relationship between heterozygosity and asymmetry: a test across the distribution range.

The genetic basis of developmental stability, as measured by bilateral asymmetry, has been debated for over 50 years among developmental and evolutionary biologists. One of the central theories dealing with this relationship suggests that higher levels of genetic diversity, as reflected in heterozygosity, result in increased stability during development and thus in lower asymmetry. In this study, we aimed to test the relationship between asymmetry and heterozygosity at two levels: (1) the population level, where mean heterozygosity within a population is predicted to be negatively correlated with mean population asymmetry and (2) the individual level, where the proportion of heterozygous loci of an individual and its bilateral asymmetry estimates are predicted to be negatively correlated. While previous studies often focused on local populations, work across species ranges can answer the following questions. Are levels of heterozygosity correlated with levels of developmental instability, as estimated by bilateral asymmetry? Are patterns consistent across the distribution range, from the periphery towards the core? Does the relationship between genetic stress and bilateral asymmetry depend on the degree of environmental stress? We tested heterozygosity levels in 26 loci and asymmetry in third toe length in 11 populations of the chukar partridge (Alectoris chukar) across a sharp climatic gradient in Israel from the arid periphery, through the Mediterranean-desert ecotone towards the Mediterranean areas located further away from the range boundaries. Genetic diversity, as estimated using both observed and expected heterozygosity, was not associated with asymmetry at either the population or at the individual level. Whereas heterozygosity showed a hump-shaped pattern, peaking at the ecotone, asymmetry monotonically increased towards the range periphery. We argue that whereas asymmetry may serve as a useful tool for estimating changes in environmental stress, it may not be widely applicable for estimating genetic stress.