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This Week in PNAS: Mar 11, 2014

Editor's Note: Some of the articles described below are not yet available at the PNAS site, but they are scheduled to be posted some time this week.

In the early, online edition of the Proceedings of the National Academy of Sciences, the Johannes Gutenberg University's Joachim Burger and colleagues from Germany, the UK, the Netherlands, and Ukraine provide evidence pointing to relatively recent positive selection on various pigmentation features in Europeans. With the help of allele frequency estimates generated for in ancient European samples going back thousands of years as well as samples from present-day Ukrainian individuals, the researchers saw signs of selection across three genes with well-established roles in skin, hair, and eye pigmentation traits. "Our results provide direct evidence that strong selection favoring lighter skin, hair, and eye pigmentation has been operating in European populations over the last 5,000 [years]," they write.

A team from Michigan State University, the US Department of Energy's Joint Genome Institute, and the Lawrence Berkeley National Laboratory describe an approach for doing de novo assembly of large metagenomic sequence sets. The scheme relies on a combination of pre-assembly filtering methods known as digital normalization and partitioning, the study's authors say. In their proof-of-principle analyses, they applied the approach to metagenome sequences from a simulated human gut microbiome as well as data from two massive soil metagenomes representing samples taken in an Iowa cornfield and a native prairie soil site. But while the methods made it possible to see a slew of molecular and metabolic interactions, the team notes that many predicted proteins and metagenome sequences still eluded annotation and assembly attempts.

Researchers from France and the US discuss efforts to generate Drosophila fruit flies with mosaic genomes comprised of sequences that are carefully selected and controlled. The group spanned several approaches that are currently being pursued in this model organism, including their own twin-spot generator, or TSG, method for labeling cells that have undergone inter-chromosomal recombination. "Our laboratory has been intimately involved in the development of methods that facilitate the creation of genetic mosaics in Drosophila," the team notes. "[W]e review our contributions to the development of this field and discuss a number of approaches that will improve further the tool kit for generating mosaic animals."