Lateralization of housekeeping genes in the brain of one-day old chicks

Real-time quantitative PCR is an exceptionally sensitive method that can detect even very small differences in gene expression and, as such, it is essential to use suitable reference genes. Domestic chickens are used in a wide range of studies including neurobiology, behavior, ecology and disease transmission. In recent avian gene expression experiments, 18S (18S ribosomal RNA), beta actin (ACTB) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) have frequently been used; however, there is not enough evidence that these reference genes are suitable for all types of experiments. There is considerable evidence for lateralization in numerous learning tasks and for differences in the functional contribution of the two brain hemispheres. Therefore, the purpose of this study was to identify a set of reference genes for chick brain region called an intermediate medial mesopallium (IMM), which is connected with memory formation in the chick brain, whilst also taking into consideration the differences between the left and right hemispheres. This study evaluated the expression stability of eleven candidate housekeeping genes in the IMM region of the 1-day old chick brain. In our experimental system, the most reliable results were given by the NormFinder algorithm. The results show for the first time that ACTB, commonly used as an avian reference gene, is not suitable for investigation of gene expression in the chick brain and that brain lateralization exact selection of different reference gens for each hemisphere. For memory process investigations using tasks in one-day old chicks the most effective reference genes for the left hemisphere were HMBS and SDHA, and for the right hemisphere the most effective was RPL19.     

Phenotypic and genomic plasticity of alternative male reproductive tactics in sailfin mollies

A major goal of modern evolutionary biology is to understand the causes and consequences of phenotypic plasticity, the ability of a single genotype to produce multiple phenotypes in response to variable environments. While ecological and quantitative genetic studies have evaluated models of the evolution of adaptive plasticity, some long-standing questions about plasticity require more mechanistic approaches. Here, we address two of those questions: does plasticity facilitate adaptive evolution? And do physiological costs place limits on plasticity? We examine these questions by comparing genetically and plastically regulated behavioural variation in sailfin mollies (Poecilia latipinna), which exhibit striking variation in plasticity for male mating behaviour. In this species, some genotypes respond plastically to a change in the social environment by switching between primarily courting and primarily sneaking behaviour. In contrast, other genotypes have fixed mating strategies (either courting or sneaking) and do not display plasticity. We found that genetic and plastic variation in behaviour were accompanied by partially, but not completely overlapping changes in brain gene expression, in partial support of models that predict that plasticity can facilitate adaptive evolution. We also found that behavioural plasticity was accompanied by broader and more robust changes in brain gene expression, suggesting a substantial physiological cost to plasticity. We also observed that sneaking behaviour, but not courting, was associated with upregulation of genes involved in learning and memory, suggesting that sneaking is more cognitively demanding than courtship.     

Tip off the HAT– Epigenetic control of learning and memory by Drosophila Tip60

Disruption of epigenetic gene control mechanisms involving histone acetylation in the brain causes cognitive impairment, a debilitating hallmark of most neurodegenerative disorders. Histone acetylation regulates cognitive gene expression via chromatin packaging control in neurons. Unfortunately, the histone acetyltransferases (HATs) that generate such neural epigenetic signatures and their mechanisms of action remain unclear. Our recent findings provide insight into this question by demonstrating that Tip60 HAT action is critical for morphology and function of the mushroom body (MB), the learning and memory center in the Drosophila brain. We show that Tip60 is robustly produced in MB Kenyon cells and extending axonal lobes and that targeted MB Tip60 HAT loss results in axonal outgrowth disruption. Functional consequences of loss and gain of Tip60 HAT levels in the MB are evidenced by defects in memory. Tip60 ChIP-Seq analysis reveals enrichment for genes that function in cognitive processes and accordingly, key genes representing these pathways are misregulated in the Tip60 HAT mutant fly brain. Remarkably, increasing levels of Tip60 in the MB rescues learning and memory deficits resulting from Alzheimer's disease associated amyloid precursor protein (APP) induced neurodegeneration. Our studies highlight the potential of HAT activators as a therapeutic option for cognitive disorders.     

Tip off the HAT– Epigenetic control of learning and memory by Drosophila Tip60

Disruption of epigenetic gene control mechanisms involving histone acetylation in the brain causes cognitive impairment, a debilitating hallmark of most neurodegenerative disorders. Histone acetylation regulates cognitive gene expression via chromatin packaging control in neurons. Unfortunately, the histone acetyltransferases (HATs) that generate such neural epigenetic signatures and their mechanisms of action remain unclear. Our recent findings provide insight into this question by demonstrating that Tip60 HAT action is critical for morphology and function of the mushroom body (MB), the learning and memory center in the Drosophila brain. We show that Tip60 is robustly produced in MB Kenyon cells and extending axonal lobes and that targeted MB Tip60 HAT loss results in axonal outgrowth disruption. Functional consequences of loss and gain of Tip60 HAT levels in the MB are evidenced by defects in memory. Tip60 ChIP-Seq analysis reveals enrichment for genes that function in cognitive processes and accordingly, key genes representing these pathways are misregulated in the Tip60 HAT mutant fly brain. Remarkably, increasing levels of Tip60 in the MB rescues learning and memory deficits resulting from Alzheimer''s disease associated amyloid precursor protein (APP) induced neurodegeneration. Our studies highlight the potential of HAT activators as a therapeutic option for cognitive disorders.     

Programs of Gene Expression During the Laying Down of Memory Formation as Revealed by DNA Microarrays

Many experiments in the past have demonstrated the requirement of de novo gene expression during memory formation. In contrast to the initial reductionistic view that genes relevant to learning and memory would be easily found and would provide a simple key to understand this brain function, it is becoming apparent that the genetic contribution to memory is complex. Previous approaches have been focused on individual genes or genetic pathways and failed to address the massively parallel nature of genome activities and collective behavior of the genes that ultimately control the molecular mechanisms underlying brain function. In view of the broad variety of genes and the cross talk of genetic pathways involved in this regulation, only gene expression profiles may reflect the complete behavior of regulatory pathways. In this review we illustrate how DNA microarray-based gene expression profiling may help to dissect and analyze the complex mechanisms involved in gene regulation during the acquisition and storage of memory in the mammalian brain.     

雌激素受体与脑肿瘤

雌激素通过其受体对脑结构与功能具有重要的调节作用,如调节脑结构的性别差异、生殖行为、神经可塑性与学习记忆等。脑肿瘤是一种危害严重的肿瘤,研究表明肿瘤细胞表达的雌激素受体的种类、水平与脑肿瘤的生长过程相关。雌激素受体可通过直接作用或与部分其它受体相互作用,调控相关基因的转录,进而调节肿瘤的生长、增殖、转移、扩散以及凋亡等生理、生化过程。本文就雌激素受体在肿瘤细胞的表达水平、表达种类以及雌激素受体参与的信号通路做一简要综述。     

Gene expression analysis following olfactory learning in Apis mellifera

The honeybee has a strong learning and memory ability, and is recognized as the best model organism for studying the neurobiological basis of learning and memory. In this study, we analyzed the gene expression difference following proboscis extension response-based olfactory learning in the A. mellifera using a tag-based digital gene expression (DGE) method. We obtained about 5.71 and 5.65 million clean tags from the trained group and untrained group, respectively. A total of 259 differentially expressed genes were detected between these two samples, with 30 genes up-regulated and 229 genes down-regulated in trained group compared to the untrained group. These results suggest that bees tend to actively suppress some genes instead of activating previously silent genes after olfactory learning. Our DGE data provide comprehensive gene expression information for olfactory learning, which will facilitate our understanding of the molecular mechanism of honey bee learning and memory.     

Hippocampal Gene Expression Meta-Analysis Identifies Aging and Age-Associated Spatial Learning Impairment (ASLI) Genes and Pathways

A number of gene expression microarray studies have been carried out in the past, which studied aging and age-associated spatial learning impairment (ASLI) in the hippocampus in animal models, with varying results. Data from such studies were never integrated to identify the most significant ASLI genes and to understand their effect. In this study we integrated these data involving rats using meta-analysis. Our results show that proper removal of batch effects from microarray data generated from different laboratories is necessary before integrating them for meta-analysis. Our meta-analysis has identified a number of significant differentially expressed genes across age or across ASLI. These genes affect many key functions in the aged compared to the young rats, which include viability of neurons, cell-to-cell signalling and interaction, migration of cells, neuronal growth, and synaptic plasticity. These functional changes due to the altered gene expression may manifest into various neurodegenerative diseases and disorders, some of which leading into syndromic memory impairments. While other aging related molecular changes can result into altered synaptic plasticity simply causing normal aging related non-syndromic learning or spatial learning impairments such as ASLI.     

The usefulness of the spontaneously hypertensive rat to model attention-deficit/hyperactivity disorder (ADHD) may be explained by the differential expression of dopamine-related genes in the brain

Spontaneously hypertensive rats (SHR) are considered to represent a genetic animal model for attention-deficit hyperactivity disorder (ADHD). In the present studies, we compared the locomotor activity, learning and memory functions of juvenile male SHR, with age- and gender-matched genetic control Wistar-Kyoto rats (WKY). In addition, we investigated potential differences in brain morphology by magnetic resonance imaging (MRI). In other complimentary studies of the central nervous system, we used real-time PCR to examine the levels of several dopaminergic-related genes, including those coding for the five major subtypes of dopamine receptor (D1, D2, D3, D4 and D5), those coding for enzymes responsible for synthesizing tyrosine hydroxylase and dopamine-beta-hydroxylase, and those coding for the dopamine transporter. Our data revealed that SHR were more active than WKY in the open field (OF) test. Also, SHR appeared less attentive, exhibiting inhibition deficit, but in the absence of memory deficits relative to spatial learning. The MRI studies revealed that SHR had a significantly smaller vermis cerebelli and caudate-putamen (CPu), and there was also a significantly lower level of dopamine D4 receptor gene expression and protein synthesis in the prefrontal cortex (PFC) of SHR. However, there were no significant differences between the expression of other dopaminergic-related genes in the midbrain, prefrontal cortex, temporal cortex, striatum, or amygdala of SHR and WKY. The data are similar to the situation seen in ADHD patients, relative to normal volunteers, and it is possible that the hypo-dopaminergic state involves a down regulation of dopamine D4 receptors, rather than a general down-regulation of catecholamine synthesis. In conclusion, the molecular and behavioural data that we obtained provide new information that may be relevant to understanding ADHD in man.     

意大利蜜蜂哺育蜂学习记忆相关基因的转录组学分析

【目的】筛选与意大利蜜蜂Apis mellifera ligustica哺育蜂学习记忆密切相关的基因。【方法】在人工组建意大利蜜蜂蜂群中收集10日龄哺育蜂、21日龄哺育蜂、21日龄采集蜂,通过喙伸反应(proboscis extension reflex, PER)实验测定这3组样本之间学习记忆能力的差异。利用RNA-seq技术对具有学习能力和不具有学习能力的10日龄哺育蜂和21日龄哺育蜂脑中基因表达量进行全面分析,筛选出与哺育蜂学习记忆密切相关的差异表达基因(DEGs),并对这些差异表达基因进行GO和KEGG富集分析。qPCR检测随机选取的3个DEGs(上调基因TpnCⅢa和MED23以及下调基因Pkc)在具有学习能力和不具有学习能力的10日龄哺育蜂和21日龄哺育蜂脑中的表达量。【结果】PER实验结果显示,经过5次训练后,意大利蜜蜂21日龄哺育蜂的学习能力显著高于10日龄哺育蜂的,而21日龄哺育蜂和21日龄采集蜂的学习能力无显著差异;同样地,21日龄哺育蜂的记忆能力显著高于10日龄哺育蜂的,而21日龄哺育蜂和21日龄采集蜂的记忆能力无显著差异。RNA-seq分析筛选到88个与哺育蜂学习记忆密切相关的DEGs,其中18个上调表达,70个下调表达。GO富集结果显示,上调DEGs在生物学进程分类中富集的基因数最多,主要富集在信号转导、蛋白质加工修饰相关;下调DEGs也是在生物学进程分类中富集的基因数最多,主要富集在转录、信号转导、蛋白质生物合成相关,其中显著性富集在转录相关。KEGG富集结果显示,下调DEGs显著性富集在吞噬、光转导、AGE-RAGE信号通路。qPCR结果显示差异表达基因TpnCⅢa,MED23和Pkc在具有学习能力和不具有学习能力的10日龄哺育蜂和21日龄哺育蜂脑中的表达水平的变化趋势与RNA-seq数据中的变化趋势一致。【结论】PER实验表明日龄是影响意大利蜜蜂哺育蜂的学习和记忆能力的重要因素;同时本研究获得学习后哺育蜂脑部的基因表达变化趋势和富集分析,为深入研究哺育蜂学习记忆的分子机制奠定了重要的理论基础。     

Learning in honeybees: from molecules to behaviour

Studies in a variety of organisms as diverse as molluscs, insects, birds and mammals have shown that memories can exist in a variety of temporal domains ranging from short-term memories in the range of minutes to long-term memories lasting a lifetime. While transient covalent modifications of proteins underlie short-term memory, the formation of long-term memory requires gene expression and protein synthesis. Different intracellular signalling cascades have been implicated in distinct aspects of learning and memory formation. Little is known however, about how learning in intact animals is related to the modulation of these signalling cascades and how this contributes to distinct neuronal and behavioural changes in vivo. Associative learning in the honeybee provides the opportunity to study processes of memory formation by analysing its progression through different phases, across levels of behaviour, neural circuits, and cellular signalling pathways. The findings reveal evidence that various cellular signalling pathways in the neuronal circuit of distinct brain areas play a role in different processes during learning and memory formation.     

Effector CD4+ T cell expression signatures and immune-mediated disease associated genes

Genome-wide association studies (GWAS) in immune-mediated diseases have identified over 150 associated genomic loci. Many of these loci play a role in T cell responses, and regulation of T cell differentiation plays a critical role in immune-mediated diseases; however, the relationship between implicated disease loci and T cell differentiation is incompletely understood. To further address this relationship, we examined differential gene expression in na?ve human CD4+ T cells, as well as in in vitro differentiated Th1, memory Th17-negative and Th17-enriched CD4+ T cells subsets using microarray and RNASeq. We observed a marked enrichment for increased expression in memory CD4+ compared to na?ve CD4+ T cells of genes contained among immune-mediated disease loci. Within memory T cells, expression of disease-associated genes was typically increased in Th17-enriched compared to Th17-negative cells. Utilizing RNASeq and promoter methylation studies, we identified a differential regulation pattern for genes solely expressed in Th17 cells (IL17A and CCL20) compared to genes expressed in both Th17 and Th1 cells (IL23R and IL12RB2), where high levels of promoter methylation are correlated to near zero RNASeq levels for IL17A and CCL20. These findings have implications for human Th17 celI plasticity and for the regulation of Th17-Th1 expression signatures. Importantly, utilizing RNASeq we found an abundant isoform of IL23R terminating before the transmembrane domain that was enriched in Th17 cells. In addition to molecular resolution, we find that RNASeq provides significantly improved power to define differential gene expression and identify alternative gene variants relative to microarray analysis. The comprehensive integration of differential gene expression between cell subsets with disease-association signals, and functional pathways provides insight into disease pathogenesis.     

Gene expression changes in GABA(A) receptors and cognition following chronic ketamine administration in mice

Ketamine is a well-known anesthetic agent and a drug of abuse. Despite its widespread use and abuse, little is known about its long-term effects on the central nervous system. The present study was designed to evaluate the effect of long-term (1- and 3-month) ketamine administration on learning and memory and associated gene expression levels in the brain. The Morris water maze was used to assess spatial memory and gene expression changes were assayed using Affymetrix Genechips; a focus on the expression of GABA(A) receptors that mediate a tonic inhibition in the brain, was confirmed by quantitative real-time PCR and western blot. Compared with saline controls, there was a decline in learning and memory performance in the ketamine-treated mice. Genechip results showed that 110 genes were up-regulated and 136 genes were down-regulated. An ontology analysis revealed the most significant effects of ketamine were on GABA(A) receptors. In particular, there was a significant up-regulation of both mRNA and protein levels of the alpha 5 subunit (Gabra5) of the GABA(A) receptors in the prefrontal cortex. In conclusion, chronic exposure to ketamine impairs working memory in mice, which may be explained at least partly by up-regulation of Gabra5 subunits in the prefrontal cortex.     

Rhes is involved in striatal function

The development and the function of central nervous system depend on thyroid hormones. In humans, the lack of thyroid hormones causes cretinism, a syndrome of severe mental deficiency. It is assumed that thyroid hormones affect the normal development and function of the brain by activating or suppressing target gene expression because several genes expressed in the brain have been shown to be under thyroid hormone control. Among these, the Rhes gene, encoding a small GTP-binding protein, is predominantly expressed in the striatal region of the brain. To clarify the role of Rhes in vivo, we disrupted the Rhes gene by homologous recombination in embryonic stem cells and generated mice homozygous for the Rhes null mutation (Rhes(-/-)). Rhes(-/-) mice were viable but weighed less than wild-type mice. Furthermore, they showed behavioral abnormalities, displaying a gender-dependent increase in anxiety levels and a clear motor coordination deficit but no learning or memory impairment. These results suggest that Rhes disruption affects selected behavioral competencies.