Volume 44 Issue 11, November 2012

Cellular transformation in cancer has long been associated with aberrant DNA methylation, most notably, hypermethylation of promoter sequences. A new study uses a clever approach of selective high-resolution profiling to follow DNA methylation over a time course of cellular transformation and challenges the notion that hypermethylation in cancer arises in an orchestrated fashion.

Three papers characterizing human germline mutation rates bolster evidence for a relatively low rate of base substitution in modern humans and highlight a central role for paternal age in determining rates of mutation. These studies represent the advent of a transformation in our understanding of mutation rates and processes, which may ultimately have public health implications.

Many SNPs associated with human disease are located in non-coding regions of the genome. A new study shows that SNPs associated with breast cancer risk are located in enhancer regions and alter binding affinity for the pioneer factor FOXA1.

Ross Levine, Lambert Busque and colleagues report the identification of recurrent somatic mutations in TET2 in elderly female individuals with clonal hematopoiesis. The mutations were identified in individuals without clinically apparent hematological malignancies.

Nick Orr and colleagues report a genome-wide association study for male breast cancer. They identify a new susceptibility locus at RAD51B and examine association evidence for known female breast cancer loci in these cohorts.

Adrienne Flanagan and colleagues identify a common variant in the T gene associated with strong risk of chordoma, a rare malignant bone tumor. The risk variant alters an amino acid in the DNA-binding domain of the T transcription factor and is associated with differential expression of T and its downstream targets.

Samuel Berkovic and colleagues report the identification of missense mutations in KCNT1, which encodes a sodium-gated potassium channel, that cause severe autosomal dominant nocturnal frontal lobe epilepsy.

Mathieu Lupien, Jason Moore and colleagues show that breast cancer risk–associated SNPs commonly disrupt the binding of FOXA1 to chromatin, thereby directly affecting gene expression.

Jan Molenaar and colleagues show that LIN28B is overexpressed and amplified in human neuroblastomas and that LIN28B regulates let-7 family miRNAs and MYCN. They create a transgenic mouse model of LIN28B overexpression and show that these mice develop neuroblastoma tumors.

Amos Tanay and colleagues characterize DNA methylation polymorphism within cell populations and track immortalized fibroblasts in culture for over 300 generations to show that formation of differentially methylated regions occurs through a stochastic process and nearly deterministic epigenetic remodeling.

Gordon Dougan and colleagues report whole-genome sequencing of a global collection of 179 Salmonella Typhimurium isolates, including 129 diverse sub-Saharan African isolates associated with invasive disease. They determine the phylogenetic structure of invasive Salmonella Typhimurium in sub-Saharan Africa and find that the majority are from two closely related highly conserved lineages, which emerged in the last 60 years in close temporal association with the current HIV epidemic.

Mayumi Tamari and colleagues report a genome-wide association study for atopic dermatitis, a chronic inflammatory skin disease, in a Japanese population. They identify eight new susceptibility loci for atopic dermatitis and compare their results to those of previous studies in European and Chinese populations.

Peter Gregersen and colleagues identify a regulatory variant in CSK, coding for an intracellular kinase that physically interacts with Lyp (PTPN22), associated with systemic lupus erythematosus (SLE). Their work suggests that the Lyp-Csk complex influences susceptibility to SLE through regulation of B-cell signaling, maturation and activation.

Yinghao Sun and colleagues report a genome-wide association study for prostate cancer in Han Chinese men. They identify two new risk-associated loci at chromosomes 9q31 and 19q13.

José Martin-Subero and colleagues report whole-genome bisulfite sequencing and methylome analysis of two CLLs and three B-cell subpopulations using high-density microarrays on 139 CLLs. They identify widespread hypomethylation in the gene body that is largely associated with intragenic enhancer elements.

Yanick Crow and colleagues show that mutations in ADAR1 cause the autoimmune disorder Aicardi-Goutières syndrome, accompanied by upregulation of interferon-stimulated genes. ADAR1 encodes an enzyme that catalyzes the deamination of adeonosine to inosine in double-stranded RNA, and the findings suggest a possible role for RNA editing in limiting the accumulation of repeat-derived RNA species.

Harry Dietz and colleagues report the identification of mutations in SKI in Shprintzen-Goldberg syndrome, which shares features with Marfan syndrome and Loeys-Dietz syndrome. SKI encodes a known repressor of TGF-β activity, and this work provides evidence for paradoxical increased TGF-β signaling as the mechanism underlying these related syndromes.

Rima Nabbout and colleagues report the identification of de novo mutations in the KCNT1 potassium channel gene in individuals with malignant migrating partial seizures of infancy, a rare epileptic encephalopathy with pharmacoresistant seizures and developmental delay. The authors show that the mutations have a gain-of-function effect on KCNT1 channel activity.

Christopher Walsh and colleagues identify mutations in CHMP1A in human cerebellar hypoplasia and microcephaly. Cells lacking CHMP1A show decreased cell proliferation and decreased expression of BMI1, a negative regulator of stem cell proliferation.

Zubair Ahmed and colleagues identify homozygous mutations in CIB2, a gene that encodes a calcium- and integrin-binding protein, that cause Usher syndrome type 1J and nonsyndromic deafness DFNB48. CIB2 is required for hair cell development and retinal photoreceptor cells in zebrafish and Drosophila melanogaster.

Irwin McLean and colleagues report that heterozygous loss-of-function mutations in AAGAB, which encodes a cytosolic protein implicated in vesicular trafficking, cause punctate palmoplantar keratoderma. They further show that knockdown of AAGAB in keratinocytes leads to increased cell proliferation accompanied by highly elevated levels of epidermal growth factor receptor.

Evan Eichler and colleagues report an estimate of the mutation rate in humans that is based on the whole-genome sequences of five parent-offspring trios from a Hutterite population and genotyping data from an extended pedigree. They use a new approach for estimating the mutation rate over multiple generations that takes into account the extensive autozygosity in this founder population.

Patrick Chinnery, Nils-Goran Larsson and colleagues show that mitochondrial heteroplasmy levels are principally determined prenatally within the developing female germline in mice transmitting a heteroplasmic single base-pair deletion in the mitochondrial tRNA^Met gene.