A phenotype-driven ENU mutagenesis screen for the identification of dominant mutations involved in alcohol consumption

The aim of this study was the application of a phenotype-driven N-ethyl-N-nitrosourea (ENU) mutagenesis screen in mice for the identification of dominant mutations involved in the regulation and modulation of alcohol-drinking behavior. The chemical mutagen ENU was utilized in the generation of 131 male ENU-mutant C57BL/6J mice (G0). These ENU-treated mice were paired with wild-type C57BL/6J mice to generate G1 and subsequent generations. In total, 3327 mice were generated. Starting with G1, mice were screened for voluntary oral self-administration of 10% (v/v) alcohol vs. water in a two-bottle paradigm. From these mice, after a total period of 5 weeks of drinking, 43 mutants fulfilled the criteria of an “alcohol phenotype,” that is, high or low ethanol intake. They were then selected for breeding and tested in a “confirmation cross” (G2–G4) for inheritance. Although we did not establish stable high or low drinking lines, several results were obtained in the context of alcohol consumption. First, female mice drank more alcohol than their male counterparts. Second, the former demonstrated greater infertility. Third, all animals displayed relatively stable alcohol intake, although significantly different in two different laboratories. Finally, seasonal and monthly variability was observed, with the highest alcohol consumption occurring in spring and the lowest in autumn. In conclusion, it seems difficult to identify dominant mutations involved in the modulation or regulation of voluntary alcohol consumption via a phenotype-driven ENU mutagenesis screen. In accordance with the findings from knockout studies, we suggest that mainly recessive mutations contribute to an alcohol-drinking or alcohol-avoiding phenotype.     

Quantitative Microscopy: Protein Dynamics and Membrane Organisation

The mobility of membrane proteins is a critical determinant of their interaction capabilities and protein functions. The heterogeneity of cell membranes imparts different types of motion onto proteins; immobility, random Brownian motion, anomalous sub-diffusion, 'hop' or confined diffusion, or directed flow. Quantifying the motion of proteins therefore enables insights into the lateral organisation of cell membranes, particularly membrane microdomains with high viscosity such as lipid rafts. In this review, we examine the hypotheses and findings of three main techniques for analysing protein dynamics: fluorescence recovery after photobleaching, single particle tracking and fluorescence correlation spectroscopy. These techniques, and the physical models employed in data analysis, have become increasingly sophisticated and provide unprecedented details of the biophysical properties of protein dynamics and membrane domains in cell membranes. Yet despite these advances, there remain significant unknowns in the relationships between cholesterol-dependent lipid microdomains, protein-protein interactions, and the effect of the underlying cytoskeleton. New multi-dimensional microscopy approaches may afford greater temporal and spatial resolution resulting in more accurate quantification of protein and membrane dynamics in live cells.     

The influence of environmental conditions on the body mass of Barn Swallows (Hirundo rustica) during spring migration

The present study examines the effects of seven microclimatic factors on the arrival body mass of migrant Barn Swallows (Hirundo rustica) in the Aiguamolls de l’Empordà Natural Park, a site located in northeastern Spain. We used principal component analysis, followed by a general linear model procedure, to create a model that examines the relationships between body mass and weather-related events recently experienced during the spring migration. Our results suggest that local weather variation during the migratory flight clearly affects the body mass of Barn Swallows on a short time scale. This effect demonstrates the importance of the environmental conditions en route for migrating swallows and how these conditions might influence diverse events of the life cycle, such as the arrival time at the breeding grounds or the reproductive success.     

Tectonic vicariance versus Messinian dispersal in western Mediterranean ground beetles

The complex geological history of the western Mediterranean region conceals the interpretation of the evolutionary history of its current fauna, as similar distribution patterns may have very different temporal and geographic origins. Particularly intriguing are some subterranean species in islands, which origin is usually difficult to interpret as their strongly modified morphologies obscure their relationships. We studied subterranean taxa and their likely relatives of two groups of ground beetles in the western Mediterranean: the Duvalius lineage (“isotopic” Trechini) and Molopina (Pterostichini). We included specimens from the islands of Mallorca, Sardinia and Sicily, plus mainland Europe and North Africa. Phylogenetic relationships were reconstructed with a combination of mitochondrial and nuclear data, and divergence dates were estimated with Bayesian methods using the same a priori molecular evolutionary rates for the same gene fragments in the two groups. In the Duvalius lineage, the subgenus Trechopsis, including all the highly modified cave or nivicolous species, was found to be polyphyletic: the species from Mallorca was found to be of Pleistocene origin and sister to the less modified species of subgenus Duvalius from the same island, whereas the Algerian species of Trechopsis were, on the contrary, related to the Sicilian Duvalius, indicating a northern colonisation route during the late Pliocene. Molopina was divided into three main lineages: the genera Abax, Percus, and the Molops groups of genera. The basal diversification of the latter was dated within a temporal window (35–25 Ma) fully congruent with the tectonic opening of the western Mediterranean basin and included six main lineages with uncertain relationships among them: the epigean genera (a) Molops and (b) Tanythrix; and the subterranean (c) Typhlochoromus (Eastern Alps), (d) Speomolops (Sardinia), (e) Henrotius (Mallorca) and (f) a strongly supported clade including the Pyrenean genera Zariquieya, Oscadytes and Molopidius. Despite the similar distribution of some of their subterranean taxa, the two studied groups show a strongly contrasting origin and mode of diversification. While the Duvalius lineage had a recent origin, with complex colonisation patterns and widespread morphological convergence among the subterranean species, the subterranean Molopina had an ancient vicariant origin resulting from the tectonic opening of the western Mediterranean basin.     

A likelihood ratio approach for identifying three-quarter siblings in genetic databases

The detection of family relationships in genetic databases is of interest in various scientific disciplines such as genetic epidemiology, population and conservation genetics, forensic science, and genealogical research. Nowadays, screening genetic databases for related individuals forms an important aspect of standard quality control procedures. Relatedness research is usually based on an allele sharing analysis of identity by state (IBS) or identity by descent (IBD) alleles. Existing IBS/IBD methods mainly aim to identify first-degree relationships (parent–offspring or full siblings) and second degree (half-siblings, avuncular, or grandparent–grandchild) pairs. Little attention has been paid to the detection of in-between first and second-degree relationships such as three-quarter siblings (3/4S) who share fewer alleles than first-degree relationships but more alleles than second-degree relationships. With the progressively increasing sample sizes used in genetic research, it becomes more likely that such relationships are present in the database under study. In this paper, we extend existing likelihood ratio (LR) methodology to accurately infer the existence of 3/4S, distinguishing them from full siblings and second-degree relatives. We use bootstrap confidence intervals to express uncertainty in the LRs. Our proposal accounts for linkage disequilibrium (LD) by using marker pruning, and we validate our methodology with a pedigree-based simulation study accounting for both LD and recombination. An empirical genome-wide array data set from the GCAT Genomes for Life cohort project is used to illustrate the method.Subject terms: Genetic markers, Population genetics