Reduction of excessive Kcnn2 activity ameliorates learning disability in the mouse model of Fetal Alcohol Spectrum Disorders
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ABSTRACT: Learning disabilities are hallmarks of congenital conditions caused by prenatal exposure to harmful agents. This is particularly true for patients suffering from Fetal Alcohol Spectrum Disorders (FASD) who exhibit a wide range of cognitive deficiencies including impaired motor skill development. While these effects have been well characterized, the molecular effects that bring about these behavioral consequences remain to be determined. We have previously found that the acute molecular responses to alcohol in the embryonic brain are stochastic, varying among neural progenitor cells. However, the pathophysiological consequences stemming from these heterogeneous responses remain unknown. Here we show that acute responses to alcohol in progenitor cells lead to altered gene expression in their descendant neurons at the single-cell level. Among the altered genes, we found that an increase of the calcium-activated potassium channel Kcnn2 in subset neurons in the motor cortex correlates with motor skill learning deficits in the mouse model of FASD. We further show that postnatal blocking of Kcnn2 improves these learning deficits. These results propose Kcnn2 blockers as a novel intervention for learning disabilities in FASD and possibly for other neurocognitive conditions.
Project description:Experience-dependent gene expression reshapes neural circuits, permitting learning of knowledge and skills. However, the diversity of plasticity-related transcriptional responses across neurons underlying learning remains poorly understood. Here, we analyzed single-nucleus transcriptomes of L2/3 glutamatergic neurons of the primary motor cortex after motor skill training or home-cage control in water-restricted mice.
Project description:We are searching for common gene expression alteration in the hippocampus of animal models of learning disabilities and in post-mortem human tissues derived from patients with cognitive deficits. Our study has three phases. In phase I, we want to investigate the changes in gene expression in a transgenic mouse line that shows impairments in hippocampal-dependent learning. These animals are overexpressing the RNA-binding protein HuD in the forebrain under the control of the alpha CAMKinII promoter. For phase II, we plan to characterize the hippocampus of another animal model of learning disabilities: fetal alcohol exposed (FAE) rats. Last, for phase III, we would like to examine gene expression changes in the hippocampus and other tissues from patients with schizophrenia. To test our hypothesis, in phase 2 of our project, we propose to compare the pattern of gene expression in our mouse model with that in the hippocampus of rats prenatally exposed to alcohol (FAE model). Our hypothesis is that learning disabilities have common neural substrates regardless of the origin of the disability being genetic, environmental of a combination of these two. To test this hypothesis, we plan to examine the pattern of gene expression in the hippocampus of animals and humans with cognitive deficits and use bioinformatics tools to identify common changes in gene expression in three of such conditions: a genetic model (HuD transgenic mice), an environmental model (FAE rats) and a model for combined environmental and genetic effects (patients with schizophrenia). All the animals are adult male Sprague-Dawley rats (age 90-100 days). Animals were divided in three diet groups and three experimental treatment conditions (9 conditions altogether). Three groups of pregnant rat dams were placed on different diet regimens: a liquid diet containing 5% alcohol (A) groups, a control group fed an isocaloric liquid diet without alcohol (B) and a group of rats fed lab chow ad libitum (C). Offspring from each of these groups were allowed to grow until adulthood and placed into each of three training groups: a contextual fear conditioned group (1), a non-learning stress control group (2) and a naive/unhandled group (3). Hippocampi were dissected and used to isolate total RNA from each rat diet and training condition. Initially, we will submit 18 samples as follows: 10 samples from training group 1 and 8 samples from training group 3 (training group 2 will be analyzed at a later date). The diet assignment for the 18 samples is: 8 samples from group A, 6 samples of group B and 4 samples of group C. Please note that I was able to enter only the first 8 samples, as the sample list does not hold 18 samples altogether.
Project description:Background: Fetal alcohol spectrum disorder (FASD) is a developmental disorder that manifests through a range of cognitive, adaptive, physiological, and neurobiological deficits resulting from prenatal alcohol exposure. Although the North American prevalence is currently estimated at 2-5%, FASD has proven difficult to identify in the absence of the overt physical features characteristic of fetal alcohol syndrome. As interventions may have the greatest impact at an early age, accurate biomarkers are needed to identify children at risk for FASD. Building on our previous work identifying distinct DNA methylation patterns in children and adolescents with FASD, we have attempted to validate these associations in a different clinical cohort and to use our DNA methylation signature to develop a possible epigenetic predictor of FASD. Methods: Genome-wide DNA methylation patterns were analyzed using the Illumina HumanMethylation450 array in the buccal epithelial cells of a cohort of 48 individuals aged 3.5-18 (24 FASD cases, 24 controls). The DNA methylation predictor of FASD was built using a stochastic gradient boosting model on our previously published dataset FASD cases and controls (GSE80261). The predictor was tested on the current dataset and an independent dataset of 48 autism spectrum disorder cases and 48 controls (GSE50759). Results: We validated findings from our previous study that identified a DNA methylation signature of FASD, replicating the altered DNA methylation levels of 161/648 CpGs in this independent cohort, which may represent a robust signature of FASD in the epigenome. We also generated a predictive model of FASD using machine learning in a subset of our previously published cohort of 179 samples (83 FASD cases, 96 controls), which was tested in this novel cohort of 48 samples and resulted in a moderately accurate predictor of FASD status. Upon testing the algorithm in an independent cohort of individuals with autism spectrum disorder, we did not detect any bias towards autism, sex, age, or ethnicity. Conclusion: These findings further support the association of FASD with distinct DNA methylation patterns, while providing a possible entry point towards the development of epigenetic biomarkers of FASD.
Project description:Maternal alcohol consumption during pregnancy results in a spectrum of lifelong behavioral and cognitive deficits collectively known as Fetal Alcohol Spectrum Disorders (FASD). FASD is a major health burden in most societies, there is no cure, and the molecular mechanism involved in its development is poorly understood. Human neurodevelopment is a continuum that extends over two decades after birth, with the potential to influence outcomes both prenatally and postnatally. Here, we experimentally investigate if positive postnatal environment enrichment ameliorates behavioral deficits caused by ethanol exposure. Furthermore, we assessed if this modulation is associated with alterations in hippocampal gene expression. To accomplish this, we used a binge model of ethanol exposure followed by environmental enrichment in C57BL/6 mice to generate four groups of animals: (1) control mice raised in standard conditions, (2) mice raised in enriched environments, (3) ethanol-exposed mice raised in standard conditions, and (4) ethanol-exposed mice raised in enriched environments. The environmental enrichment includes larger home cages with more individuals for social interaction, regular exposure to novel items, and access to running wheels. Ethanol exposure results in anxiety-like behavior (light-dark box) as well as learning and memory deficits (Barnes maze) that are at least partially ameliorated by enrichment. Environmental enrichment also improves performance for individuals not exposed to ethanol. Ethanol exposure induces changes in adult hippocampal gene expression (RNA-Seq). Some of the changes in adult hippocampal gene expression following ethanol exposure are reversed by environmental enrichment. The results offer a potential mechanism of behavioral deficits caused by ethanol exposure, including the potential for amelioration after an FASD diagnosis.
Project description:Prenatal alcohol exposure is the leading preventable cause of behavioural and cognitive deficits, which may affect between 2-5% of children in North America. While the underlying mechanisms of alcohol’s effects on development remain relatively unknown, emerging evidence implicates epigenetic mechanisms in mediating the range of symptoms observed in children with Fetal Alcohol Spectrum Disorder (FASD). Thus, we investigated the effects of prenatal alcohol exposure on genome-wide DNA methylation in the NeuroDevNet FASD cohort, the largest cohort of human FASD samples to date. Genome-wide DNA methylation patterns of buccal epithelial cells were analyzed using the Illumina HumanMethylation450 array on a Canadian cohort of 206 children (110 FASD and 96 controls). Genotyping was performed in parallel using the Infinium HumanOmni2.5-Quad v1.0 BeadChip. After correcting for the effects of genetic background, 658 significantly differentially methylated sites between FASD cases and controls remained, with 41 displaying differences in beta greater than 5%. Furthermore, 203 differentially methylated regions containing 2 or more CpGs were also identified, overlapping with 167 different genes. The majority of differentially methylated genes were highly expressed in samples from the Allen Brain Atlas, which showed high correlations with buccal cell DNA methylation patterns. Furthermore, over-representation analysis of the up-methylated genes displayed a significant enrichment for neurodevelopmental processes and diseases, such as anxiety, epilepsy, and autism spectrum disorders. These findings suggest that prenatal alcohol exposure is associated with distinct DNA methylation patterns in children and adolescents, raising the possibility of an epigenetic biomarker of FASD.
Project description:CTCF is an organizer of higher-order chromatin structure, and regulates gene expression. Genetic studies have implicated mutations in CTCF in intellectual disabilities. However, there is no knowledge of the role of CTCF-mediated chromatin structure in learning and memory. We show that depletion of CTCF in postmitotic neurons, or depletion in the hippocampus of adult mice through viral-mediated knockout, induces deficits in learning and memory. These deficits in learning and memory at the beginning of adulthood are correlated with impaired long term potentiation and reduced spine density, with no changes in basal synaptic transmission and dendritic morphogenesis and arborization. Cognitive disabilities are associated with downregulation of cadherin and learning-related genes. In addition, CTCF knockdown attenuates fear conditioning-induced hippocampal gene expression of key learning genes and loss of long-range interactions at the BDNF and Arc loci. This study identifies CTCF-dependent gene expression regulation and DNA structure as regulators of learning and memory.
Project description:CTCF is an organizer of higher-order chromatin structure, and regulates gene expression. Genetic studies have implicated mutations in CTCF in intellectual disabilities. However, there is no knowledge of the role of CTCF-mediated chromatin structure in learning and memory. We show that depletion of CTCF in postmitotic neurons, or depletion in the hippocampus of adult mice through viral-mediated knockout, induces deficits in learning and memory. These deficits in learning and memory at the beginning of adulthood are correlated with impaired long term potentiation and reduced spine density, with no changes in basal synaptic transmission and dendritic morphogenesis and arborization. Cognitive disabilities are associated with downregulation of cadherin and learning-related genes. In addition, CTCF knockdown attenuates fear conditioning-induced hippocampal gene expression of key learning genes and loss of long-range interactions at the BDNF and Arc loci. This study identifies CTCF-dependent gene expression regulation and DNA structure as regulators of learning and memory.
Project description:We are searching for common gene expression alteration in the hippocampus of animal models of learning disabilities and in post-mortem human tissues derived from patients with cognitive deficits. Our study has three phases. In phase I, we want to investigate the changes in gene expression in a transgenic mouse line that shows impairments in hippocampal-dependent learning. These animals are overexpressing the RNA-binding protein HuD in the forebrain under the control of the alpha CAMKinII promoter. For phase II, we plan to characterize the hippocampus of another animal model of learning disabilities: fetal alcohol exposed (FAE) rats. Last, for phase III, we would like to examine gene expression changes in the hippocampus and other tissues from patients with schizophrenia. To test our hypothesis, in phase 2 of our project, we propose to compare the pattern of gene expression in our mouse model with that in the hippocampus of rats prenatally exposed to alcohol (FAE model). Our hypothesis is that learning disabilities have common neural substrates regardless of the origin of the disability being genetic, environmental of a combination of these two. To test this hypothesis, we plan to examine the pattern of gene expression in the hippocampus of animals and humans with cognitive deficits and use bioinformatics tools to identify common changes in gene expression in three of such conditions: a genetic model (HuD transgenic mice), an environmental model (FAE rats) and a model for combined environmental and genetic effects (patients with schizophrenia). All the animals are adult male Sprague-Dawley rats (age 90-100 days). Animals were divided in three diet groups and three experimental treatment conditions (9 conditions altogether). Three groups of pregnant rat dams were placed on different diet regimens: a liquid diet containing 5% alcohol (A) groups, a control group fed an isocaloric liquid diet without alcohol (B) and a group of rats fed lab chow ad libitum (C). Offspring from each of these groups were allowed to grow until adulthood and placed into each of three training groups: a contextual fear conditioned group (1), a non-learning stress control group (2) and a naive/unhandled group (3). Hippocampi were dissected and used to isolate total RNA from each rat diet and training condition. Initially, we will submit 18 samples as follows: 10 samples from training group 1 and 8 samples from training group 3 (training group 2 will be analyzed at a later date). The diet assignment for the 18 samples is: 8 samples from group A, 6 samples of group B and 4 samples of group C. Please note that I was able to enter only the first 8 samples, as the sample list does not hold 18 samples altogether. Keywords: dose response
Project description:Alcohol use disorder (AUD) is a life-threatening disease characterized by compulsive drinking, cognitive deficits, and social impairment that continue despite negative consequences, which are driven by dysfunction of cortical areas, such as the orbitofrontal cortex (OFC), that normally balances decisions related to reward and risk. In this study, proteomics and machine learning analysis of post-mortem OFC brain samples collected from individuals with AUD revealed dysregulation of presynaptic (e.g., AP2A1) and mitochondrial proteins that predicted the occurrence and severity of AUD. Alcohol-sensitive OFC proteins also mapped to abnormal social behaviors and interactions. Validation using reverse genetics, we found that prefrontal Ap2a1 regulates alcohol drinking in genetically diverse mouse strains. Furthermore, we demonstrated sexual dimorphism in human OFC proteins that regulate extracellular matrix structure and signaling. Together, these findings highlight the impact of excessive alcohol consumption on the human OFC proteome and identify important cross-species cortical mechanisms underlying AUD.
Project description:Exposure to alcohol during early embryonic or fetal development has been linked with a variety of adverse outcomes, the most common of which are structural and functional abnormalities of the central nervous system. Behavioral and cognitive deficits reported in individuals exposed to alcohol in utero include intellectual impairment, learning and memory difficulties, diminished executive functioning, attention problems, poor motor function and hyperactivity. The economic and social costs of these outcomes are substantial and profound. Improvement of neurobehavioural outcomes following prenatal alcohol exposure requires greater understanding of the mechanisms of alcohol-induced damage to the brain. Here we use a mouse model of relatively moderate ethanol exposure early in pregnancy and profile gene expression in the hippocampus and caudate putamen of adult male offspring. The effects of offspring sex and age on ethanol-sensitive hippocampal gene expression were also examined.