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Archive - Apr 26, 2018

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44 Genetic Risk Factors Identified for Major Depression

A global research project has mapped out the genetic basis of major depression, identifying 44 genetic variants which are risk factors for depression, 30 of which are newly discovered. The study, by the Psychiatric Genomics Consortium, and co-led in the UK by King's College London, is the largest study to-date of genetic risk factors for major depression. Published online on April 26, 2018 in Nature Genetics, the research finds that the genetic basis for major depression is shared with other psychiatric disorders such as schizophrenia, and that all humans carry at least some of the 44 genetic risk factors identified in the study. The article is titled “Genome-Wide Association Analyses Identify 44 Risk Variants and Refine the Genetic Architecture of Major Depression.” A significant number of the genetic variants identified in the study are directly linked to the targets of current antidepressant medications. Analysis of the data also suggests that having a higher body mass index (BMI) is linked to an increased risk of major depression. Previous studies have struggled to identify more than a handful of genetic variants associated with depression. By combining seven separate datasets, the research team included data on more than 135,000 people with major depression and more than 344,000 controls. The study was an unprecedented global effort by over 200 scientists who work with the Psychiatric Genomics Consortium, and was led by the University of North Carolina School of Medicine and the University of Queensland in Australia. Professor Cathryn Lewis and Dr. Gerome Breen of King's College London led the UK contribution, along with scientists and psychiatrists from the Universities of Edinburgh, Cardiff, and University College London (UCL).

Mystery Deepens—Organism’s Apparent Lack of Sex Not Related to Dessication-Based DNA Repair As Previously Thought; Organism Does Undergo Unusual Amount of Horizontal Gene Transfer; Sexual Reproduction Cannot Yet Be Ruled Out

A new study has cast doubt on leading theory for how tiny creatures have evolved for tens of millions of years - without ever having sex. Most animals reproduce sexually, a process which shuffles genes from parent to offspring. This makes natural selection more efficient and allows animals to evolve defenses against changing environmental conditions more rapidly, especially new diseases. Bdelloid rotifers however appear to be an exception to this rule: they are all female, and their offspring are clones of their mothers. Bdelloids are microscopic animals that live in freshwater and damp habitats across the world. Despite their apparent lack of sex, we know they have evolved for tens of millions of years into more than 500 species. By studying their genomes - the set of all the genes that define an animal's characteristics - researchers thought they had identified an explanation for how bdelloids had 'gotten away' with no sex for millions of years. However, a new study, published online on April 24, 2018 in PLOS Biology and led by Imperial College London researchers, reveals this mechanism may not be the main explanation for the bdelloids' success. The article is titled “Comparative Genomics of Bdelloid Rotifers: Insights from Desiccating and Nondesiccating Species.” Many species of bdelloid endure periods of drying out, called desiccation. Although they survive desiccation, the process damages their DNA, which they need to repair when rehydrated. Based on results of a previous study of the genome of a species that survives desiccation, researchers had proposed that the repair of DNA might remove some of the problems of being asexual, for example by removing harmful mutations and possibly allowing occasional recombination of genes to occur.