In the early, online edition of the Proceedings of the National Academy of Sciences, researchers from France and Italy outline findings from an effort to characterize diatom communities using nearly 300 ocean samples collected from 46 sites around the world during the Tara Oceans expedition. The team used targeted sequencing to determine diatom community composition and diversity at these sites, focusing on metabarcodes containing the hypervariable V9 region of the 18S ribosomal RNA gene. From the millions of ribotype sequences they generated, the authors uncovered diatom representatives from more than 4,700 operational taxonomic units. A few turned up consistently across the sampled sites, they note, though the overall communities differed depending on the ocean area considered.
A Memorial Sloan Kettering Cancer Center-led team considers the consequences of PTEN tumor suppressor gene loss in breast carcinoma — mutations previously implicated in breast cancer progression and treatment resistance in individuals with HER2-amplified breast cancers. Through a series of experiments using a genetically engineered mouse model designed to have temporary, inducible PTEN expression in mammary gland tissue, the researchers found evidence that PTEN suppression leads to enhanced signaling through the PI3-kinase and KAP kinase pathways due to altered interactions with HER2, spurring cancer progression. "Our findings imply that even advanced tumors can remain dependent on Pten loss," they write, "and provide a rationale for exploring the utility of MEK inhibitors in therapy-resistant breast cancer patients acquiring PTEN mutations."
Finally, an international team led by researchers at the University of Florida and the Massachusetts Institute of Technology describe a DNA modification system detected in a Salmonella enterica serovar and several other bacterial species. After identifying the modifications in the S. enterica serovar Montevideo, the researchers did comparative gene cluster analyses on a broad range of bacteria phyla to find still other examples of the modifying gene cluster, a bacterial genomic island capable of inserting so-called 7-deazaguanine derivatives into DNA. "The extensive lateral transfer of the gene cluster responsible for this modification highlights its significance as a previously unrecognized DNA defense system that bacteria and phages use to protect their genomes," the study's authors say.