In an advance, online publication of Nature this week, an international research team reports their sequencing and analysis of the freshwater cnidarian Hydra magnipapillata genome, as compared to the genomes of the anthozoan Nematostella vectensis and other animals: "The Hydra genome has been shaped by bursts of transposable element expansion, horizontal gene transfer, trans-splicing, and simplification of gene structure and gene content that parallel simplification of the Hydra life cycle," the authors write. They suggest that comparisons of the Hydra genome to those of other animals have helped them to elucidate the organism's evolution of epithelia, contractile tissues, and developmentally regulated transcription factors, among other things.
Also published online in advance, European researchers report their sequencing of the mRNA portion of the transcriptome in 60 HapMap individuals of European ancestry. The team quantified exon abundance based upon read depth and found that nearly "10 million reads of sequencing can provide access to the same dynamic range as arrays with better quantification of alternative and highly abundant transcripts." Additionally, correlation with SNPs led to a larger discovery of expression quantitative trait loci than with arrays, the researchers write. They suggest that high-throughput sequencing technologies are capable of illuminating the properties of genetic effects on the transcriptome.
In this week's issue of Nature, researchers in Spain and the US present their determination that compensatory evolution in mammalian mitochondrial tRNAs, wherein it effectively affixes two alleles that are individually deleterious, could be a common phenomenon. The team examined the "fitness landscapes traversed by switches" between nucleotide pairs at complimentary sites of mitochondrial tRNA in 83 species. Compensatory evolution must occur through rare intermediate variants that never reach fixation, the authors suggest.
In an advance, online publication of Nature Genetics this week, researchers present results from their genome-wide association study for ulcerative colitis, which identified risk loci at 7q22 and 22q13. Their analysis included 1,897,764 SNPs from 1,043 UC cases and 1,703 controls from Germany, and confirmed risk associations in six replication panels from different regions of Europe.