In Nature this week, researchers report the genome sequences for a monozygotic twin pair — discordant for multiple sclerosis — as well as mRNA transcriptome and epigenome sequences of CD4+ lymphocytes from three MS-discordant, monozygotic twin pairs. "No reproducible differences were detected between co-twins among ~3.6 million single nucleotide polymorphisms or ~0.2 million insertion-deletion polymorphisms," the authors write, adding "nor were any reproducible differences observed between siblings of the three twin pairs in HLA haplotypes, confirmed MS-susceptibility SNPs, copy number variations, mRNA and genomic SNP and insertion-deletion genotypes, or the expression of ~19,000 genes in CD4+ T cells." The authors note that theirs is the first effort to evaluate variation between monozygotic twins; though they did not find "epigenetic or transcriptome differences that explained disease discordance," the team reports the first female, twin, and autoimmune disease genome sequences.
In a research article published online in advance in Nature, investigators in the US and Australia present evidence of a "dicer-independent miRNA biogenesis pathway that requires Ago catalysis." Using a genetically engineered mouse model with catalytically inactive Ago2 alleles, the team found that "homozygous mutants died shortly after birth with an obvious anemia." Additionally, by examining miRNAs and their potential targets in the model, they found a loss of miR-451 — known to be important in erythropoeiesis. The authors suggest that their study connects the conservation of Ago "catalysis to a conserved mechanism of microRNA biogenesis that is important for vertebrate development."
An international research team reports a 213-base-pair inversion of the SCR — male specificity — gene they found in 95 percent of European accessions of Arabidopsis, "contrasting with the genome-wide pattern of polymorphism" in the species. When the team inverted the 213-bp inversion for expression in transgenic Wei-1 plants, the functional SCR gene restored the self-incompatibility mechanism. "The inversion within SCR is the first mutation disrupting [self-incompatibility] shown to be nearly fixed in geographically wide samples," the authors suggest.
A trio of papers in Nature Genetics this week report meta-analyses of genome-wide association studies for smoking behavior. Collaborators at the Tobacco and Genetics Consortium, DeCode Genetics, and the Oxford-GlaxoSmithKline study, among several of their colleagues, confirm loci for smoking behavior in three large cohorts. The Ox-GSK study confirmed "an effect on smoking quantity at a locus on [chromosome] 15q25, that includes CHRNA5, CHRNA3 and CHRNB4, three genes encoding neuronal nicotinic acetylcholine receptor subunits," they write, a finding which the TAG Consortium also confirmed.