Population genetic structure and colonisation history of the tool-using New Caledonian crow

New Caledonian crows exhibit considerable variation in tool making between populations. Here, we present the first study of the species' genetic structure over its geographical distribution. We collected feathers from crows on mainland Grande Terre, the inshore island of Toupéti, and the nearby island of Maré where it is believed birds were introduced after European colonisation. We used nine microsatellite markers to establish the genotypes of 136 crows from these islands and classical population genetic tools as well as Approximate Bayesian Computations to explore the distribution of genetic diversity. We found that New Caledonian crows most likely separate into three main distinct clusters: Grande Terre, Toupéti and Maré. Furthermore, Toupéti and Maré crows represent a subset of the genetic diversity observed on Grande Terre, confirming their mainland origin. The genetic data are compatible with a colonisation of Maré taking place after European colonisation around 1900. Importantly, we observed (1) moderate, but significant, genetic differentiation across Grande Terre, and (2) that the degree of differentiation between populations on the mainland increases with geographic distance. These data indicate that despite individual crows' potential ability to disperse over large distances, most gene flow occurs over short distances. The temporal and spatial patterns described provide a basis for further hypothesis testing and investigation of the geographical variation observed in the tool skills of these crows.     

Cancer genes hypermethylated in human embryonic stem cells

Developmental genes are silenced in embryonic stem cells by a bivalent histone-based chromatin mark. It has been proposed that this mark also confers a predisposition to aberrant DNA promoter hypermethylation of tumor suppressor genes (TSGs) in cancer. We report here that silencing of a significant proportion of these TSGs in human embryonic and adult stem cells is associated with promoter DNA hypermethylation. Our results indicate a role for DNA methylation in the control of gene expression in human stem cells and suggest that, for genes repressed by promoter hypermethylation in stem cells in vivo, the aberrant process in cancer could be understood as a defect in establishing an unmethylated promoter during differentiation, rather than as an anomalous process of de novo hypermethylation.     

Chromosome mapping in Alealigenes eutrophus CH34

Mutants and mobilizing plasmids were developed as genetic tools in Alcaligenes eutrophus CH34. In order to map the chromosome, spontaneous and ethyl methane sulphonate (EMS)-induced mutants (mostly auxotrophs) were isolated. Another source of mutants was provided by the phenomenon of temperature-induced mortality and mutagenesis that is observed at 37° C and is characteristic of many metallotolerant strains of A. eutrophus. Plasmid pULB113 (RP4::miniMu) was used to map the available mutations. Twenty-five loci were ordered in a circular map. pMOL50, a rearranged derivative of plasmid pMOL28, which was obtained in a survivor at 37° C and displayed chromosome mobilizing activity (Cma+), was also used to mobilize chromosomal markers: resulting linkages were stronger than with pULB113, allowing confirmation of the circularity of the A. eutrophus CH34 chromosome with a small number of crosses.     

Silencing of the Cav3.2 T-type calcium channel gene in sensory neurons demonstrates its major role in nociception

Analgesic therapies are still limited and sometimes poorly effective, therefore finding new targets for the development of innovative drugs is urgently needed. In order to validate the potential utility of blocking T-type calcium channels to reduce nociception, we explored the effects of intrathecally administered oligodeoxynucleotide antisenses, specific to the recently identified T-type calcium channel family (CaV3.1, CaV3.2, and CaV3.3), on reactions to noxious stimuli in healthy and mononeuropathic rats. Our results demonstrate that the antisense targeting CaV3.2 induced a knockdown of the CaV3.2 mRNA and protein expression as well as a large reduction of 'CaV3.2-like' T-type currents in nociceptive dorsal root ganglion neurons. Concomitantly, the antisense treatment resulted in major antinociceptive, anti-hyperalgesic, and anti-allodynic effects, suggesting that CaV3.2 plays a major pronociceptive role in acute and chronic pain states. Taken together, the results provide direct evidence linking CaV3.2 T-type channels to pain perception and suggest that CaV3.2 may offer a specific molecular target for the treatment of pain.     

Estimation of Canine Leishmania Infection Prevalence in Six Cities of the Algerian Littoral Zone Using a Bayesian Approach

A large-scale study on canine Leishmania infection (CanL) was conducted in six localities along a west-east transect in the Algerian littoral zone (Tlemcen, Mostaganem, Tipaza, Boumerdes, Bejaia, Jijel) and covering two sampling periods. In total 2,184 dogs were tested with an indirect fluorescent antibody test (IFAT) and a direct agglutination test (DAT). Combined multiple-testing and several statistical methods were compared to estimate the CanL true prevalence and tests characteristics (sensitivity and specificity). The Bayesian full model showed the best fit and yielded prevalence estimates between 11% (Mostaganem, first period) and 38% (Bejaia, second period). Sensitivity of IFAT varied (in function of locality) between 86% and 88% while its specificity varied between 65% and 87%. DAT was less sensitive than IFAT but showed a higher specificity (between 80% and 95% in function of locality or/and season). A general increasing trend of the CanL prevalence was noted from west to east. A concordance between the present results and the incidence of human cases of visceral leishmaniasis was observed, where also a maximum was recorded for Bejaia. The results of the present study highlight the dangers when using IFAT as a gold standard.     

Isolation of polysaccharide-free DNA from plants

A quick procedure for the isolation of polysaccharide-free DNA from different plant species and cell suspension or callus cultures is described. The originality of the method lies in the use of a mixture of glycoside hydrolases that leads, after phenol and chloroform extraction, to the isolation of pure DNA without any polysaccharide contamination. The highly purified DNA can be used for nucleotide analysis by HPLC, RFLP analysis and PCR amplification.     

Genetic structure and functioning of alien ship rat populations from a Corsican micro-insular complex

The detrimental effects of the introduced ship rat on bird species on the Lavezzi Mediterranean archipelago has led to the decision to eradicate the rodent from the main island, Lavezzu (73 ha), as well as from several neighbouring islets. A genetic study using eight microsatellite markers has revealed some of the dynamics of this rat population. First, it has been shown that the rat population was genetically stable (no departure from Hardy-Weinberg equilibrium and no linkage disequilibrium) and as suggested by paleontological data, established for a long time. This information is encouraging in term of viability of the eradication campaign in the long term, even if rare immigration events cannot be excluded. Second, this study shows that rats are likely to swim between the main island and the islets quite regularly since no clear genetic differentiation has been detected between them. This result is quite surprising since the ship rat is not known for its swimming abilities. Third, a cryptic genetic structure has been detected on the main island, with the north peninsula differentiated from the rest. This result correlates the observation of particular predation behaviours only observed in this part of the island. Finally, evolutionary hypotheses (e.g., dispersal limitation, emergence of family groups, local adaptation) are discussed to explain the genetic patterns observed and the population functioning inferred. These results should be of particular interest to wildlife managers concerned with rat eradications, and also provide clear insights into the study of other biological invasions.