Volume 47 Issue 10, October 2015

Pancreatic cancers consist of a heterogeneous amalgam of assorted cell types, making it challenging to develop a classification system that groups these tumors according to common molecular features. A new study tackles this important issue using bioinformatics approaches to decipher gene expression signatures derived specifically from either tumor cells or nonmalignant stromal cells that predict patient outcome and may inform personalized treatments.

Adeno-associated virus (AAV) vectors have been widely adopted for use in gene therapy. A new study raises concerns regarding this approach, reporting that chromosomal insertions of AAV serotype 2 seem to activate proto-oncogenes in human hepatocellular carcinoma.

The three-dimensional organization of the genome has an important role in orchestrating gene expression, but its regulation is poorly understood. Now, a new study uncovers a major role for Polycomb components of the PRC1 complex in organizing physical networks of genes that are co-repressed to maintain pluripotency.

Gil McVean and colleagues report a meta-analysis of Immunochip studies including over 17,000 multiple sclerosis cases and 30,000 controls, with imputation of classical HLA alleles. They find two interactions involving class II HLA alleles but no evidence for significant epistatic interactions or interactions between HLA and non-HLA risk variants.

Jian Yang and colleagues present a method, GREML-LDMS, to estimate heritability for complex human traits using whole-genome sequencing data or imputation with the 1000 Genomes Project reference panel. Using the heritability estimates from GREML-LDMS, they find that there is negligible missing heritability for human height and BMI.

Hugh Watkins, Sekar Kathiresan, Ruth McPherson, Martin Farrall and colleagues report the results of a large genome-wide association meta-analysis of coronary artery disease based on 1000 Genomes imputation. They identify ten new risk loci and show that susceptibility to this disease is largely determined by common SNPs with small effect sizes.

Isabelle Plo, Christine Bellanné-Chantelot, William Vainchenker and colleagues report a 700-kb germline duplication including the ATG2B and GSKIP genes in four related families with myeloid malignancy predisposition. Using induced pluripotent stem cells and primary cells, they demonstrate that ATG2B and GSKIP enhance hematopoietic progenitor differentiation.

Laurent Frantz and colleagues report an analysis of 103 whole genomes from European and Asian wild boars and domestic pigs. They find evidence in support of a complex domestication model with gene flow from wild populations counteracted by recurrent artificial selection for traits important for domestication.

Wei Li, Qianben Wang and colleagues analyze genome-wide epigenetic patterns in tumor and normal tissues and find that broad H3K4me3 peaks are associated with increased transcription elongation and are enriched at tumor-suppressor genes. They demonstrate that this epigenetic mark may be used to identify new candidate tumor-suppressor genes.

Roderic Guigó, Montserrat Corominas and colleagues find that histone marks associated with active chromatin are absent from genes with high expression during specific developmental stages in both Drosophila melanogaster and Caenorhabditis elegans. They observe similar patterns for genes with high levels of transcriptional variation across mammalian tissues and cell types.

Jen Jen Yeh and colleagues apply statistical methods to separate tumor, stroma and normal tissue gene expression signatures from pancreatic ductal adenocarcinoma expression profiling data sets. They identify and validate two tumor-specific and two stroma-specific subtypes, which are associated with different clinical outcomes.

Sarah Elderkin and colleagues show that PRC1 acts as a master regulator of genome architecture in mouse embryonic stem cells by organizing genes in three-dimensional interaction networks. They find that the strongest spatial network is composed of the four Hox clusters and key early developmental transcription factor genes, and they propose that selective release of genes from this spatial network underlies cell fate specification during embryonic development.

Jessica Zucman-Rossi and colleagues identify clonal integrations of adeno-associated virus type 2 (AAV2) in hepatocellular carcinomas. These AAV2 integrations occurred within known cancer driver genes, suggesting a pathogenic role of AAV2 in these patients.

Boris Bastian and colleagues report the results of exome sequencing of desmoplastic melanoma. They identify recurrent NFKBIE promoter mutations and diverse mutations leading to activation of the MAPK pathway.

Francois Le Loarer, Franck Tirode and colleagues identify a new class of undifferentiated thoracic sarcomas characterized by inactivation of SMARCA4, which encodes an ATPase subunit of BAF chromatin-remodeling complexes. They further show that these tumors exhibit transcriptional profiles similar to those of other BAF-deficient malignancies.

Christian Dina, Nabila Bouatia-Naji, Xavier Jeunemaitre and colleagues from the Leducq Transatlantic MITRAL Network report the results of a genome-wide association study of nonsyndromic mitral valve prolapse. They identify six susceptibility loci and provide functional evidence implicating LMCD1 and TNS1 as genes influencing mitral valve development.

Kornelia Polyak, Franziska Michor and colleagues report a novel method, STAR-FISH, for combined in situ single-cell analysis of point mutations and copy number alterations in archived tissue samples. They apply STAR-FISH to clinically relevant PIK3CA mutations and HER2 amplifications and observe associations between intratumoral diversity and clinical outcome.