Saturday, November 8, 2008

New Research of Interest

[RNA interference as antiviral strategy]
[Article in German]
Neumann-Haefelin C, Blum HE, Thimme R.
Abteilung Innere Medizin II, Universitätsklinikum Freiburg.
RNA interference is the inhibition of gene expression at the level of messenger RNA (mRNA) mediated by small RNA molecules. Small interfering RNA (siRNA) is an important immune defence mechanism in plants and non-vertebrates. In addition, synthetic siRNAs can be used to inhibit gene expression also in human cells. More than 500 microRNAs (miRNAs), however, are involved in the natural regulation of gene expression in humans, e. g., in development-specific gene expression in embryogenesis or organ development. Although a role of miRNAs in antiviral immune defence has been discussed for some time, only recently virus-promoting as well as antiviral properties of defined miRNAs have been identified in hepatitis C virus (HCV) infection. The understanding of the mechanisms of action of miRNA might lead to new antiviral and preventive strategies.
PMID: 18988133 [PubMed - in process]

: Genetica. 2008 Sep;134(1):5-19. Epub 2007 Jul 7.
The genetic basis of traits regulating sperm competition and polyandry: can selection favour the evolution of good- and sexy-sperm?
Evans JP, Simmons LW.
Centre for Evolutionary Biology, School of Animal Biology M092, The University of Western Australia, Nedlands, WA, Australia.
The good-sperm and sexy-sperm (GS-SS) hypotheses predict that female multiple mating (polyandry) can fuel sexual selection for heritable male traits that promote success in sperm competition. A major prediction generated by these models, therefore, is that polyandry will benefit females indirectly via their sons' enhanced fertilization success. Furthermore, like classic 'good genes' and 'sexy son' models for the evolution of female preferences, GS-SS processes predict a genetic correlation between genes for female mating frequency (analogous to the female preference) and those for traits influencing fertilization success (the sexually selected traits). We examine the premise for these predictions by exploring the genetic basis of traits thought to influence fertilization success and female mating frequency. We also highlight recent debates that stress the possible genetic constraints to evolution of traits influencing fertilization success via GS-SS processes, including sex-linked inheritance, nonadditive effects, interacting parental genotypes, and trade-offs between integrated ejaculate components. Despite these possible constraints, the available data suggest that male traits involved in sperm competition typically exhibit substantial additive genetic variance and rapid evolutionary responses to selection. Nevertheless, the limited data on the genetic variation in female mating frequency implicate strong genetic maternal effects, including X-linkage, which is inconsistent with GS-SS processes. Although the relative paucity of studies on the genetic basis of polyandry does not allow us to draw firm conclusions about the evolutionary origins of this trait, the emerging pattern of sex linkage in genes for polyandry is more consistent with an evolutionary history of antagonistic selection over mating frequency. We advocate further development of GS-SS theory to take account of the complex evolutionary dynamics imposed by sexual conflict over mating frequency.
PMID: 17619174 [PubMed - indexed for MEDLINE]

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