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PNAS Papers on Kleine-Levin Syndrome GWAS, Non-Coding RNA Methylation Imprinting, More

Editor's Note: Some of the articles described below are not yet available at the PNAS site, but they are scheduled to be posted this week.

An international team led by investigators at Stanford University presents findings from a genome-wide association study focused on a rare condition called Kleine-Levin syndrome (KLS) that is marked by episodes of excess sleep, cognitive impairment, and other symptoms. Using array-based genotyping profiles for 673 individuals over 14 years old with KLS and more than 15,300 unaffected controls from similar ancestral backgrounds, the researchers narrowed in on a KLS-associated region that spanned 20 SNPs in and around the bipolar disorder- and schizophrenia-related gene TRANK1 in the original cohort. The KLS-related region did not track with the condition in another set of 171 KLS cases, they note, though it remained associated in a subset of cases that involved children with difficult births. The authors suggest "variants in the TRANK1 gene region may predispose to KLS when patients have had a difficult birth, suggesting that [the] TRANK1 gene region modulates newborns' response to brain injury, with consequences for mental and neurological health in adulthood."

A team from the US and South Africa report on apparent ties between maternal age and alcohol consumption and DNA methylation-based imprinting on nc886 — a non-coding RNA that falls in a stretch of sequence that is silenced on the maternally inherited allele in most individuals, despite being methylated in human eggs. The researchers relied on high-resolution melt curve analyses to profile nc886 DNA methylation in on newborn blood spot or cord blood samples from 1,132 South African mother-child pairs, uncovering a maternal age-associated rise in nc886 and a dip in imprinting that coincided with alcohol consumption. "[W]e demonstrate that alcohol consumption but not cigarette smoking is associated with a lower frequency of imprinting," they report. "While most studies focus on the post-conceptional developmental time, our work indicates that maternal age and exposures the year prior to pregnancy may alter the epigenome and therefore the developing child."

Researchers from Japan, China, and elsewhere explore turnip mosaic potyvirus (TuMV) pathogen spread in Brassica vegetables and other plants, using genome sequence data and phylogenetics. Based on whole-genome sequence data for 579 TuMV isolates collected from sites in Europe and Asia over several decades, together with hundreds more partial pathogen sequences, the team used phylogenetics and molecular clock profiling to assess Eurasian TuMV emergence and spread, which coincided to some extent with trade along with Silk Road. "Many crops are believed to have spread to East Asia via the Silk Road," the authors write. "We found that TuMV was able to infect Brassica plants in the 17th century CE and spread to Eastern Eurasia over the past few centuries."