The list of the chromosome races of the common shrew (Sorex araneus)

The list of chromosome races of the common shrew (Sorex araneus) was compiled, the vast literature has been scrutinized, and unpublished data have been added. Altogether, 50 chromosome races could be listed. The name and its synonyms, chromosomal constitution, author of the description, type locality, known distribution range, and additional information are reported for individual races. The present list should be considered a working document that will be regularly updated and supplemented.

Chromosome localization of microsatellite markers in the shrews of the Sorex araneus group.

The extremely high rate of karyotypic evolution that characterizes the shrews of the Sorex araneus group makes this group an exceptionally interesting model for population genetics and evolutionary studies. Here, we attempted to map 46 microsatellite markers at the chromosome arm level using flow-sorted chromosomes from three karyotypically different taxa of the Sorex araneus group (S. granarius and the chromosome races Cordon and Novosibirsk of S. araneus). The most likely localizations were provided for 35 markers, among which 25 were each unambiguously mapped to a single locus on the corresponding chromosomes in the three taxa, covering the three sexual chromosomes (XY1Y2) and nine of the 18 autosomal arms of the S. araneus group. The results provide further evidence for a high degree of conservation in genome organization in the S. araneus group despite the presence of numerous Robertsonian rearrangements. These markers can therefore be used to compare the genetic structure among taxa of the S. araneus group at the chromosome level and to study the role of chromosomal rearrangements in the genetic diversification and speciation process of this group.

O-chromosome lethal frequencies in Serbian and Montenegrin Drosophila subobscura populations

Lethal chromosomal frequencies were obtained from three Drosophila subobscura samples from the Mt. Avala (Serbia) population in September 2003 (0.218), June 2004 (0.204) and September 2004 (0.250). These values and those from other Balkan populations studied previously (Petnica, Kamariste, Zanjic and Djerdap) were used to analyze the possible effect of population, year, month and altitude above sea level on lethal chromosomal frequencies. According to ANOVAS no effect were observed. Furthermore, the lethal frequencies of the Balkan populations did not vary according to latitude. This is probably due to the relative proximity and high gene flow between these populations. From a joint study of all the Palearctic D. subobscura populations so far analyzed, it can be deduced that the Balkan populations are located in the central area of the species distribution. Finally, it seems that lethal chromosomal frequencies are a consequence of the genetic structure of the populations.

Non-random autosome segregation: a stepping stone for the evolution of sex chromosome complexes?

A new study in Caenorhabditis elegans shows that homologous autosomes segregate non-randomly with the sex chromosome in the heterogametic sex. Segregation occurs according to size, small autosomes segregating with, and large autosomes segregating away from the X-chromosome. Such sex-biased transmission of autosomes could facilitate the spread of sexually antagonistic alleles whose effects favor the fitness of one sex at the expense of the other. This may provide a first step toward the evolution of new sex determination systems.

aIr-1, a newly found locus on mouse chromosome 16 encoding a trans-acting activator factor for MHC class II gene expression.

RJ 2.2.5 is a human B cell line that has lost the capacity to express MHC class II genes. The human class II-positive phenotype is restored in somatic cell hybrids between RJ 2.2.5 and mouse spleen cells. By karyotype and molecular studies of an informative family of hybrids we have now shown that the reexpression of human class II gene products, as well as the maintenance of the mouse class II-positive phenotype, correlates with the presence of mouse chromosome 16. Thus, the existence on this mouse chromosome of a newly found locus, designated by us aIr-1, that determines a trans-acting activator function for class II gene expression, is established. Possible implications of this finding are discussed.

Sex-chromosome differentiation parallels postglacial range expansion in European tree frogs (Hyla arborea).

Occasional XY recombination is a proposed explanation for the sex-chromosome homomorphy in European tree frogs. Numerous laboratory crosses, however, failed to detect any event of male recombination, and a detailed survey of NW-European Hyla arborea populations identified male-specific alleles at sex-linked loci, pointing to the absence of XY recombination in their recent history. Here, we address this paradox in a phylogeographic framework by genotyping sex-linked microsatellite markers in populations and sibships from the entire species range. Contrasting with postglacial populations of NW Europe, which display complete absence of XY recombination and strong sex-chromosome differentiation, refugial populations of the southern Balkans and Adriatic coast show limited XY recombination and large overlaps in allele frequencies. Geographically and historically intermediate populations of the Pannonian Basin show intermediate patterns of XY differentiation. Even in populations where X and Y occasionally recombine, the genetic diversity of Y haplotypes is reduced below the levels expected from the fourfold drop in copy numbers. This study is the first in which X and Y haplotypes could be phased over the distribution range in a species with homomorphic sex chromosomes; it shows that XY-recombination patterns may differ strikingly between conspecific populations, and that recombination arrest may evolve rapidly (<5000 generations).

Associations of serum uric acid and SLC2A9 variant with depressive and anxiety disorders: a population-based study

Background: Limited information exists regarding the association between serum uric acid (SUA) and psychiatric disorders. We explored the relationship between SUA and subtypes of major depressive disorder (MDD) and specific anxiety disorders. Additionally, we examined the association of SLC2A9 rs6855911 variant with anxiety disorders. Methods: We conducted a cross-sectional analysis on 3,716 individuals aged 35-66 years previously selected for the population-based CoLaus survey and who agreed to undergo further psychiatric evaluation. SUA was measured using uricase-PAP method. The French translation of the semi-structured Diagnostic Interview for Genetic Studies was used to establish lifetime and current diagnoses of depression and anxiety disorders according to the DSM-IV criteria. Results: Men reported significantly higher levels of SUA compared to women (357}74 μmol/L vs. 263}64 μmol/L). The prevalence of lifetime and current MDD was 44% and 18% respectively while the corresponding estimates for any anxiety disorders were 18% and 10% respectively. A quadratic hockey-stick shaped curve explained the relationship between SUA and social phobia better than a linear trend. However, with regards to the other specific anxiety disorders and other subtypes of MDD, there was no consistent pattern of association. Further analyses using SLC2A9 rs6855911 variant, known to be strongly associated with SUA, supported the quadratic relationship observed between SUA phenotype and social phobia. Conclusions: A quadratic relationship between SUA and social phobia was observed consistent with a protective effect of moderately elevated SUA on social phobia, which disappears at higher concentrations. Further studies are needed to confirm our observations.

Euphorbia L. subsect. Esula (Boiss. in DC.) Pax in the Iberian Peninsula. Leaf surface, chromosome numbers and taxonomic treatment

Presentem l'estudi taxonòmic dels représentants d'Euphorbia subsect. Esula a la Península Ibèrica. Prèviament, s'inclou un primer capítol dedicai a l'estudi de les epidermis foliars i un segon capítol sobre nombres cromosòmics...

Auto- and allopolyploidy in Centaurea sect. Acrocentron s.l. (Asteraceae, Cardueae): karyotype and chromosome banding pattern analyses

Dysploidy and polyploidy are well documented in the large genus Centaurea, especially in sect. Acrocentron and in a small group of species from the Iberian Peninsula described as sect. Chamaecyanus, closely related to Acrocentron. We have explored two interesting cases of polyploid series in both sections: the polyploid series of Centaurea toletana in sect. Chamaecyanus and the series of C. ornata group in sect. Acrocentron. We have carried out a karyological study using both classic karyotype analyses and chromosome banding with fluorochromes.

Y chromosome microsatellite isolation from BAC clones in the greater white-toothed shrew (Crocidura russula)

We constructed a microsatellite library from four Crocidura russula Y chromosome-specific bacterial artificial chromosome (BAC) clones. Only one of eight microsatellites was male-specific, despite genome walking to obtain more flanking sequence and testing of 93 primer combinations. Potential reasons for this low success are discussed. The male-specific locus, CRY3, was genotyped in 90 males, including C. russula from across the species range and two related species. The large difference in CRY3 allele size between eastern and western lineages supports earlier reports of high divergence between them. Despite polymorphism of CRY3 in Morocco, only one allele was found throughout the whole of Europe, consistent with previous studies that suggest recent colonization of Europe from a small number of Moroccan founders.

Scale-specific sex-biased dispersal in the Valais shrew unveiled by genetic variation on the Y chromosome, autosomes, and mitochondrial DNA.

We investigated sex specificities in the evolutionary processes shaping Y chromosome, autosomes, and mitochondrial DNA patterns of genetic structure in the Valais shrew (Sorex antinorii), a mountain dwelling species with a hierarchical distribution. Both hierarchical analyses of variance and isolation-by-distance analyses revealed patterns of population structure that were not consistent across maternal, paternal, and biparentally inherited markers. Differentiation on a Y microsatellite was lower than expected from the comparison with autosomal microsatellites and mtDNA, and it was mostly due to genetic variance among populations within valleys, whereas the opposite was observed on other markers. In addition, there was no pattern of isolation by distance for the Y, whereas there was strong isolation by distance on mtDNA and autosomes. We use a hierarchical island model of coancestry dynamics to discuss the relative roles of the microevolutionary forces that may induce such patterns. We conclude that sex-biased dispersal is the most important driver of the observed genetic structure, but with an intriguing twist: it seems that dispersal is strongly male biased at large spatial scale, whereas it is mildly biased in favor of females at local scale. These results add to recent reports of scale-specific sex-biased dispersal patterns, and emphasize the usefulness of the Y chromosome in conjunction with mtDNA and autosomes to infer sex specificities.

Linker insertion mutagenesis based on IS21 transposition: isolation of an AMP-insensitive variant of catabolic ornithine carbamoyltransferase from Pseudomonas aeruginosa.

The bacterial insertion sequence IS21 when repeated in tandem efficiently promotes non-replicative cointegrate formation in Escherichia coli. An IS21-IS21 junction region which had been engineered to contain unique SalI and BglII sites close to the IS21 termini was not affected in the ability to form cointegrates with target plasmids. Based on this finding, a novel procedure of random linker insertion mutagenesis was devised. Suicide plasmids containing the engineered junction region (pME5 and pME6) formed cointegrates with target plasmids in an E.coli host strain expressing the IS21 transposition proteins in trans. Cointegrates were resolved in vitro by restriction with SalI or BglII and ligation; thus, insertions of four or 11 codons, respectively, were created in the target DNA, practically at random. The cloned Pseudomonas aeruginosa arcB gene encoding catabolic ornithine carbamoyltransferase was used as a target. Of 20 different four-codon insertions in arcB, 11 inactivated the enzyme. Among the remaining nine insertion mutants which retained enzyme activity, three enzyme variants had reduced affinity for the substrate ornithine and one had lost recognition of the allosteric activator AMP. The linker insertions obtained illustrate the usefulness of the method in the analysis of structure-function relationships of proteins.

Medulloblastomas in adults: prognostic factors and lessons from paediatrics.

Purpose of reviewMedulloblastomas are very rare in adults. Usual treatment consists of craniospinal radiation with or without chemotherapy. Current efforts focus on a better understanding of tumour biology, stratifying patients into risk groups and adapting treatment accordingly. This review discusses clinical and new molecular risk factors that will help to optimize treatment in adult medulloblastoma patients.Recent findingsThe clinical risk stratification should be complemented with new molecular prognostic markers. Gene-expression profiling has permitted identification of four to six molecular medulloblastoma subgroups. The WNT subgroup shows overexpression of genes of the WNT/wingless signalling pathway with frequent mutations of the CNNTB1 gene, loss of chromosome 6 and accumulation of nuclear beta-catenin, and is most often seen in children with medulloblastomas of classical histology. This variant has a good prognosis. Activation of the sonic hedgehog pathway with frequent mutations of the PTCH and SUFU genes, loss of 9q, and positivity for GLI1 and SFRP1 is more frequent in children less than 3 years old and in adults, commonly associated with desmoplastic histology. Other subgroups are not so well defined and have overlapping characteristics, but MYC/MYCN amplification, 17q gain and, large cell/anaplastic histology are factors of poor prognosis.SummaryNew molecular subgroups will help tailor treatment and further develop new targeted therapies. Prospective and ideally randomized trials should be performed in adults, including risk stratification by molecular markers, to identify optimal treatment for each risk group.