Chipping away at memory

Inverse power-law behavior is known to be characteristic of adaptation, learning, and memory. Herein, we propose a phenomenological model of forgetting based on renewal theory that introduces a new psychophysical concept, chipping; discrete events that chip away at chunks of memory and thereby produce forgetting. The neural mechanism producing these chips is the 1/f-noise that is generically produced in complex neuronal networks.     

Chipping away at 'stemness'

Global gene-expression analyses of human embryonic stem cells confirm the involvement of some known genes in stem-cell function and identify some new candidate regulators of stem-cell growth. Support remains elusive, however, for the concept of 'stemness' - a pattern of expression of genes that is common to all stem cells.     

Chipping away at the old block

With growing concern that women are still failing to progress in scientific careers, many countries are trying to address the problem. The British government has just received a hard-hitting report with recommendations for swift action to tackle the problems. Nigel Williams reports.     

Genome-wide DNA methylation scan in major depressive disorder

While genome-wide association studies are ongoing to identify sequence variation influencing susceptibility to major depressive disorder (MDD), epigenetic marks, such as DNA methylation, which can be influenced by environment, might also play a role. Here we present the first genome-wide DNA methylation (DNAm) scan in MDD. We compared 39 postmortem frontal cortex MDD samples to 26 controls. DNA was hybridized to our Comprehensive High-throughput Arrays for Relative Methylation (CHARM) platform, covering 3.5 million CpGs. CHARM identified 224 candidate regions with DNAm differences >10%. These regions are highly enriched for neuronal growth and development genes. Ten of 17 regions for which validation was attempted showed true DNAm differences; the greatest were in PRIMA1, with 12-15% increased DNAm in MDD (p = 0.0002-0.0003), and a concomitant decrease in gene expression. These results must be considered pilot data, however, as we could only test replication in a small number of additional brain samples (n = 16), which showed no significant difference in PRIMA1. Because PRIMA1 anchors acetylcholinesterase in neuronal membranes, decreased expression could result in decreased enzyme function and increased cholinergic transmission, consistent with a role in MDD. We observed decreased immunoreactivity for acetylcholinesterase in MDD brain with increased PRIMA1 DNAm, non-significant at p = 0.08.While we cannot draw firm conclusions about PRIMA1 DNAm in MDD, the involvement of neuronal development genes across the set showing differential methylation suggests a role for epigenetics in the illness. Further studies using limbic system brain regions might shed additional light on this role.     

Dysregulation of brain dopamine systems in major depressive disorder

Major depressive disorder (MDD or depression) is a debilitating neuropsychiatric syndrome with genetic, epigenetic, and environmental contributions. Depression is one of the largest contributors to chronic disease burden; it affects more than one in six individuals in the United States. A wide array of cellular and molecular modifications distributed across a variety of neuronal processes and circuits underlie the pathophysiology of depression—no established mechanism can explain all aspects of the disease. MDD suffers from a vast treatment gap worldwide, and large numbers of individuals who require treatment do not receive adequate care. This mini-review focuses on dysregulation of brain dopamine (DA) systems in the pathophysiology of MDD and describing new cellular targets for potential medication development focused on DA-modulated micro-circuits. We also explore how neurodevelopmental factors may modify risk for later emergence of MDD, possibly through dopaminergic substrates in the brain.     

Dissecting the genetic etiology of major depressive disorder using linkage analysis

Major depressive disorder (MDD) is clinically and genetically heterogeneous. Studies suggest that recurrence, early onset and comorbid phenotypes define more genetically homogeneous sub-samples. The concordance of linkage findings in recent studies using such approaches is encouraging. Sex-specific analyses and broader phenotypes have also yielded interesting results. These findings indicate that future research should consider comorbid disorders and sex-specific analyses. However, this direction must be approached with caution, owing to the complex multiple-testing issues that arise when considering numerous related phenotypes. With appropriate interpretation, these findings indicate a new potential for positional cloning efforts to locate genes in consensus regions. Genes found might influence specific subtypes of MDD or broader phenotypes, leading to enhanced clinical characterization and management of MDD.     

Plasma metabonomics as a novel diagnostic approach for major depressive disorder

Major depressive disorder (MDD) is a socially detrimental psychiatric disorder, contributing to increased healthcare expenditures and suicide rates. However, no empirical laboratory-based tests are available to support the diagnosis of MDD. In this study, a NMR-based plasma metabonomic method for the diagnosis of MDD was tested. Proton nuclear magnetic resonance ((1)H NMR) spectra of plasma sampled from first-episode drug-na??ve depressed patients (n = 58) and healthy controls (n = 42) were recorded and analyzed by orthogonal partial least-squares discriminant analysis (OPLS-DA). The OPLS-DA score plots of the spectra demonstrated that the depressed patient group was significantly distinguishable from the healthy control group. Moreover, the method accurately diagnosed blinded samples (n = 26) in an independent replication cohort with a sensitivity and specificity of 92.8% and 83.3%, respectively. Taken together, NMR-based plasma metabonomics may offer an accurate empirical laboratory-based method applicable to the diagnosis of MDD.     

重性抑郁障碍发病的表观遗传调控假说

表观遗传学是研究主要受控于DNA甲基化、染色质结构变化的可遗传和逆转的基因组功能的调控。近年来, 越来越多的证据表明表观遗传因素在精神分裂症、双相障碍、药物成瘾等重性精神障碍的发病中扮演着重要角色。文章综述了表观遗传现象的分子机制, 介绍了表观遗传修饰与复杂性疾病的关系, 并在此基础上对重性抑郁障碍(Major depressive disorder, MDD)发病的表观遗传调控假说及最新研究进展进行了总结。     

Novel loci and potential mechanisms of major depressive disorder,bipolar disorder,and schizophrenia

Science China Life Sciences - Different psychiatric disorders share genetic relationships and pleiotropic loci to certain extent. We integrated and analyzed datasets related to major depressive...