Volume 49 Issue 7, July 2017

Promoters and enhancers have long been regarded as distinct elements, a notion that has been challenged more recently. Two new studies now identify promoters that function as long-range enhancers in vivo to regulate the transcription of distal genes.

A study in this issue demonstrates that epigenome-modifying drugs used in cancer chemotherapy induce transcription from thousands of previously unannotated transcription start sites, most of which are derived from ancient endogenous retroviruses (ERVs). This work, coupled with previous related findings, suggests that induction of ERVs, rather than direct effects on specific genes, may have a central role in the cellular responses to such agents and, in turn, their therapeutic efficacy.

A new study shows that aberrant DNA transposase activity promotes structural alterations that are clonally selected to drive tumor development. This discovery uncovers novel mechanisms of tumor-suppressor gene inactivation and highlights a new approach to cancer gene identification.

Elise Robinson and colleagues present the polygenic transmission disequilibrium test (pTDT) for evaluating transmission of polygenic risk in family-based study designs. The authors apply pTDT to a cohort of autism spectrum disorder (ASD) families and find that common polygenic variation acts additively with de novo variants to contribute to ASD risk.

By analyzing imputed genetic data for 42 human traits, Doug Speed and colleagues derive a model that describes how heritability varies with minor allele frequency, linkage disequilibrium and genotype certainty. Using this model, they show that common SNPs contribute substantially more heritability than previously thought.

Chiea Chuen Khor, Tin Aung, Francesca Pasutto, Janey Wiggs and colleagues report a global genome-wide association study of exfoliation syndrome and a fine-mapping analysis of a previously identified disease-associated locus, LOXL1. They identify a rare protective variant in LOXL1 exclusive to the Japanese population and five new common variant susceptibility loci.

Alex Kentsis and colleagues identify somatic genomic rearrangements in primary human rhabdoid tumors characterized by deletions and inversions involving PGBD5-specific signal sequences at their breakpoints. They further show that ectopic expression of PGBD5 in primary immortalized human cells is sufficient to promote cell transformation in vitro and in immunodeficient mice in vivo, thus defining PGBD5 as an oncogenic mutator and providing a plausible mechanism for site-specific DNA rearrangements in solid tumors.

Christina Curtis and colleagues simulate spatial tumor growth under different evolutionary models and compare their results to multiregion sequencing data. They find that it is possible to distinguish tumors driven by strong positive selection from those evolving neutrally or under weak selection and infer different evolutionary modes within and between tumor types.

Sudipto Roy, Carol Wicking, Carsten Bergmann and colleagues report that mutations in DZIP1L cause autosomal recessive polycystic kidney disease (ARPKD). Through studies of mouse and zebrafish models of DZIP1L loss of function, the authors demonstrate that DZIP1L is required for proper function of the periciliary diffusion barrier.

Paul Lehner and colleagues identify an essential role for MORC2 in HUSH complex–mediated epigenetic silencing. They show that loss of MORC2 causes chromatin decompaction at HUSH-target loci and that a MORC2 mutation that causes Charcot–Marie–Tooth disease results in hyperactivation of HUSH-mediated repression in neuronal cells.

Julia Zeitlinger and Wanqing Shao use ChIP-nexus to study RNA polymerase II (Pol II) promoter pausing and its relation to the formation of new initiation complexes in Drosophila cells. They find that pausing affects the initiation of new transcripts and propose that paused RNA Pol II helps to prevent new initiation between transcription bursts.

Christoph Plass and colleagues investigate the transcriptomic and epigenomic changes induced by treatment with inhibitors of DNMT and HDAC in cancer cell lines. They observe large numbers of treatment-induced non-annotated TSSs (TINATs) encoded in long-terminal repeats that are normally repressed in most cell types.

Kian Peng Koh and colleagues report that TET1 regulates lineage-specific genes in the mouse postimplantation embryo, many of them independently of DNA methylation changes, through regulation of JMJD8 expression. They show that Tet1 deletion causes embryonic defects, which are partially penetrant in an inbred strain but fully lethal in non-inbred mice.

Salvatore Spicuglia and colleagues use a high-throughput reporter assay to identify a set of mammalian promoters, termed Epromoters, that display enhancer activity and have distinct genomic and epigenomic features. Through CRISPR–Cas9 gene editing experiments, they show that Epromoters are involved in long-range gene regulation in cis.

Rajeev Varshney and colleagues resequence the whole genomes of 292 pigeonpea (Cajanus cajan) cultivars, landraces and wild species. They find genomic regions that were likely targets of domestication and perform genome-wide association analysis to identify candidate genes for agriculturally relevant traits.

Tianzhen Zhang, Xiongming Du and colleagues report whole-genome resequencing of 318 upland cotton (Gossypium hirsutum) accessions. They carried out genome-wide association analyses to identify loci associated with fiber quality, lint yield and resistance to Verticillium wilt, and identify two ethylene-pathway genes associated with the increased lint yield observed in improved cultivars.

Etienne Bucher and colleagues use a combination of short- and long-read sequencing, along with optical mapping technologies, to produce the high-quality de novo assembly of the apple genome. They identify a new repetitive retrotransposon sequence and analyze DNA methylation data in relation to important agronomic traits.

Danielle Posthuma and colleagues perform a large meta-analysis for intelligence and determine genetic overlap with several neuropsychiatric and metabolic traits. They find 15 new significant loci and implicate 40 new genes, most of which are predominantly expressed in the brain.

Joanna Howson and colleagues perform a genome-wide association study and meta-analysis for coronary artery disease in large, trans-ancestry cohorts. They identify 15 new loci and correlate these regions with cell-type-specific gene expression and plasma protein levels to find novel pathways and potential mechanisms of disease.

Yuta Kochi and colleagues perform expression quantitative trait loci (eQTL) analysis on five subsets of immune cells individually sorted from blood from 105 individuals. They develop an integrated analysis pipeline of expression and epigenomic data along with gene association to identify cell-specific candidate causal genes and apply this to rheumatoid arthritis.

Christopher Amos and colleagues perform genome-wide association analysis for lung cancer using cohorts genotyped on the OncoArray and combing these with existing data. They identify 18 loci, 10 of which are new, finding heterogeneity across the different lung cancer subtypes, and explore candidate genes through eQTL analysis in lung tissue.

Clare Turnbull and colleagues report discovery of 19 new susceptibility loci for testicular germ cell tumor (TGCT) and provide evidence for a network of physical interactions between TGCT risk variants and candidate causal genes. Their findings implicate widespread disruption of developmental transcriptional regulators in TGCT susceptibility, consistent with failed primordial germ cell differentiation as an initiating step in oncogenesis.

Katherine Nathanson, Peter Kanetsky and colleagues present a meta-analysis of five genome-wide association studies of testicular germ cell tumor (TGCT). They identify eight new susceptibility loci and new independent signals at two previously reported loci, providing further clues to the etiology of TGCT.

Nazneen Rahman, Geert Kops and colleagues report the identification of biallelic loss-of-function mutations in TRIP13 in six individuals with Wilms tumor who presented with features of mosaic variegated aneuploidy. They show that TRIP13-mutant cells show spindle assembly checkpoint defects and suggest that mechanisms leading to aneuploidy may contribute directly to increased cancer risk.

Cecilia Lo and colleagues report the recovery of mice with hypoplastic left heart syndrome (HLHS) from a large mutagenesis screen. They find genetic heterogeneity among HLHS mice and functionally validate mutations in two genes, Sap130 and Pcdha, as contributing to HLHS in a combinatorial manner.