RESEARCH HIGHLIGHTS IN BRIEF NON-CODING RNA Non-coding RNA changes enzyme specificity Y RNAs are non-coding RNAs that form ribonucleoprotein complexes with Ro proteins and are present in most metazoans and some bacterial species. Until now, the function of Y RNAs was unknown. Using structural and biochemical techniques, Chen and colleagues showed that a bacterial Y RNA acts as a scaffold for the interaction between a Ro protein and the exoribonuclease polynucleotide phosphorylase (PNPase). As a result, the specificity of PNPase is altered so that it efficiently degrades structured RNAs. ORIGINAL RESEARCH PAPER Chen, X. et al. An RNA degradation machine sculpted by Ro autoantigen and noncoding RNA. Cell 153, 166–177 (2013) CANCER GENETICS Focus on susceptibility to hormone-related cancers The Collaborative Oncological Gene–environment Study (COGS) consortium has published 13 new studies of genetic susceptibility to three hormone-related cancers: breast, ovarian and prostate. Nature Genetics presents these papers in an iCOGS Focus, which includes Research Highlights, Commentaries and Primer articles. The innovative Primer articles each pick out a theme from across the 13 studies and link back to and bring together editorial overviews with relevant excerpts from the primary papers. These themes include shared susceptibility loci between the three cancers that were studied and the implications for risk prediction and population screening. ORIGINAL RESEARCH PAPERS Nature Genetics iCOGS Focus homepage: http://www.nature.com/icogs POPULATION GENOMICS Characterizing indels Small insertions and deletions (indels) are some of the least well-characterized and least understood variants in the human genome. In this paper, the authors sequenced the genomes of 179 individuals from three populations and identified 1.6 million indels. The authors showed heterogenous rates of indel formation across the genome and found that 4.03% occur in indel hotspots. For 75% of the indels, the affected sequences were suggestive of indel formation through polymerase slippage. They also found that indel length affects evolutionary selection pressure at that region and that indels affect gene expression. ORIGINAL RESEARCH PAPER Montgomery, S. et al. The origin, evolution and functional impact of short insertion-deletion variants identified in 179 human genomes. Genome Res. 11 Mar 2013 (doi:10.1101/gr.148718.112) DNA METHYLATION Placental partially methylated domains Partially CpG-methylated domains have previously been characterized in cultured cells and cancer cells and are associated with gene repression and inactive chromatin marks. In this paper, Schroeder et al. carried out MethylC-seq in human placental tissue and identified partially methylated domains; this is the first incidence of these being identified in normal tissue. These domains were found reproducibly in placental samples throughout gestation, and genes within them were found to have tissue-specific function and were repressed. These data suggest a developmental role for these domains. ORIGINAL RESEARCH PAPER Schroeder, D. I. et al. The human placenta methylome. Proc. Natl Acad. Sci. USA 25 Mar 2013 (doi:10.1073/pnas.1215145110) NATURE REVIEWS | GENETICS VOLUME 14 | MAY 2013 © 2013 Macmillan Publishers Limited. All rights reserved.