Identification of Xiphinema index in an Austrian vineyard

Research Note

In vitro evidence for senescent multinucleated melanocytes as a source for tumor-initiating cells

Oncogenic signaling in melanocytes results in oncogene-induced senescence (OIS), a stable cell-cycle arrest frequently characterized by a bi- or multinuclear phenotype that is considered as a barrier to cancer progression. However, the long-sustained conviction that senescence is a truly irreversible process has recently been challenged. Still, it is not known whether cells driven into OIS can progress to cancer and thereby pose a potential threat. Here, we show that prolonged expression of the melanoma oncogene N-RAS61K in pigment cells overcomes OIS by triggering the emergence of tumor-initiating mononucleated stem-like cells from senescent cells. This progeny is dedifferentiated, highly proliferative, anoikis-resistant and induces fast growing, metastatic tumors. Our data describe that differentiated cells, which are driven into senescence by an oncogene, use this senescence state as trigger for tumor transformation, giving rise to highly aggressive tumor-initiating cells. These observations provide the first experimental in vitro evidence for the evasion of OIS on the cellular level and ensuing transformation

Novel putative receptor tyrosine kinase encoded by the melanoma-inducing Tu locus in Xiphophorus

No abstract availabl

Evolution of the canonical sex chromosomes of the guppy and its relatives

The sex chromosomes of the guppy, Poecilia reticulata, and its close relatives are of particular interest: they are much younger than the highly degenerate sex chromosomes of model systems such as humans and Drosophila melanogaster, and they carry many of the genes responsible for the males’ dramatic coloration. Over the last decade, several studies have analyzed these sex chromosomes using a variety of approaches including sequencing genomes and transcriptomes, cytology, and linkage mapping. Conflicting conclusions have emerged, in particular concerning the history of the sex chromosomes and the evolution of suppressed recombination between the X and Y. Here, we address these controversies by reviewing the evidence and reanalyzing data. We find no evidence of a nonrecombining sex-determining region or evolutionary strata in P. reticulata. Furthermore, we find that the data most strongly support the hypothesis that the sex-determining regions of 2 close relatives of the guppy, Poecilia wingei and Micropoecilia picta, evolved independently after their lineages diverged. We identify possible causes of conflicting results in previous studies and suggest best practices going forward

Ploidy mosaicism and allele-specific gene expression differences in the allopolyploid Squalius alburnoides

<p>Abstract</p> <p>Background</p> <p><it>Squalius alburnoides </it>is an Iberian cyprinid fish resulting from an interspecific hybridisation between <it>Squalius pyrenaicus </it>females (P genome) and males of an unknown <it>Anaecypris hispanica-</it>like species (A genome). <it>S. alburnoides </it>is an allopolyploid hybridogenetic complex, which makes it a likely candidate for ploidy mosaicism occurrence, and is also an interesting model to address questions about gene expression regulation and genomic interactions. Indeed, it was previously suggested that in <it>S. alburnoides </it>triploids (PAA composition) silencing of one of the three alleles (mainly of the P allele) occurs. However, not a whole haplome is inactivated but a more or less random inactivation of alleles varying between individuals and even between organs of the same fish was seen.</p> <p>In this work we intended to correlate expression differences between individuals and/or between organs to the occurrence of mosaicism, evaluating if mosaics could explain previous observations and its impact on the assessment of gene expression patterns.</p> <p>Results</p> <p>To achieve our goal, we developed flow cytometry and cell sorting protocols for this system generating more homogenous cellular and transcriptional samples. With this set-up we detected 10% ploidy mosaicism within the <it>S. alburnoides </it>complex, and determined the allelic expression profiles of ubiquitously expressed genes (<it>rpl8</it>; <it>gapdh </it>and <it>β-actin</it>) in cells from liver and kidney of mosaic and non-mosaic individuals coming from different rivers over a wide geographic range.</p> <p>Conclusions</p> <p>Ploidy mosaicism occurs sporadically within the <it>S. alburnoides </it>complex, but in a frequency significantly higher than reported for other organisms. Moreover, we could exclude the influence of this phenomenon on the detection of variable allelic expression profiles of ubiquitously expressed genes (<it>rpl8</it>; <it>gapdh </it>and <it>β-actin</it>) in cells from liver and kidney of triploid individuals. Finally, we determined that the expression patterns previously detected only in a narrow geographic range is not a local restricted phenomenon but is pervasive in rivers where <it>S. pyrenaicus </it>is sympatric with <it>S. alburnoides</it>.</p> <p>We discuss mechanisms that could lead to the formation of mosaic <it>S. alburnoides </it>and hypothesise about a relaxation of the mechanisms that impose a tight control over mitosis and ploidy control in mixoploids.</p

Gene copy silencing and DNA methylation in natural and artificially produced allopolyploid fish

Allelic silencing is an important mechanism to cope with gene dosage changes in polyploidy organisms that is well known in allopolyploid plants. Only recently, it was shown in the allotriploid fish Squalius alburnoides that this process also occurs in vertebrates. However, it is still unknown if this silencing mechanism is common to other allopolyploid fish; and which mechanisms might be responsible for allelic silencing (AS). We addressed these questions in a comparative study between Squalius alburnoides and another allopolyploid complex, the Amazon molly (Poecilia formosa). We examined the allelic expression patterns for three target genes in four somatic tissues of natural allo-anorthoploids and laboratory produced tri-genomic hybrids of S. alburnoides and P. formosa. Also, for both complexes, we evaluated the correlation between total DNA methylation level and the ploidy status and genomic composition of the individuals. We found that AS also occurs in other allopolyploid organisms besides the single one that was previously known. We found and discuss disparities within and between the two considered complexes concerning the pattern of allele specific expression and DNA methylation levels. Disparities might be due to intrinsic characteristics of each genome involved in the hybridization process. Our findings also support that long-term evolutionary processes have an effect onto the allele expression patterns and possibly also on DNA methylation levels.</jats:p

Diversity of immunoglobulin light chain genes in non-teleost ray-finned fish uncovers IgL subdivision into five ancient isotypes

<p>The aim of this study was to fill important gaps in the evolutionary history of immunoglobulins by examining the structure and diversity of IgL genes in non-teleost ray-finned fish. First, based on the bioinformatic analysis of recent transcriptomic and genomic resources, we experimentally characterized the IgL genes in the chondrostean fish, Acipenser ruthenus (sterlet). We show that this species has three loci encoding IgL kappa-like chains with a translocon-type gene organization and a single VJC cluster, encoding homogeneous lambda-like light chain. In addition, sterlet possesses sigma-like VL and J-CL genes, which are transcribed separately and both encode protein products with cleavable leader peptides. The Acipenseriformes IgL dataset was extended by the sequences mined in the databases of species belonging to other non-teleost lineages of ray-finned fish: Holostei and Polypteriformes. Inclusion of these new data into phylogenetic analysis showed a clear subdivision of IgL chains into five groups. The isotype described previously as the teleostean IgL lambda turned out to be a kappa and lambda chain paralog that emerged before the radiation of ray-finned fish. We designate this isotype as lambda-2. The phylogeny also showed that sigma-2 IgL chains initially regarded as specific for cartilaginous fish are present in holosteans, polypterids, and even in turtles. We conclude that there were five ancient IgL isotypes, which evolved differentially in various lineages of jawed vertebrates.</p

High tandem repeat content in the genome of the short-lived annual fish Nothobranchius furzeri: a new vertebrate model for aging research

A genomic analysis of the annual fish Nothobranchius furzeri, a vertebrate with the shortest known life span in captivity and which may provide a new model organism for aging research

Considerations for a European animal welfare standard to evaluate adverse phenotypes in teleost fish

No abstract available