Modified Snake α-Neurotoxin Averts ß-Amyloid Binding to α7 Nicotinic Acetylcholine Receptor and Reverses Cognitive Deficits in Alzheimer's Disease Mice.

Alzheimer's disease (AD) is the most common cause of senile dementia and one of the greatest medical, social, and economic challenges. According to a dominant theory, amyloid-ß (Aß) peptide is a key AD pathogenic factor. Aß-soluble species interfere with synaptic functions, aggregate gradually, form plaques, and trigger neurodegeneration. The AD-associated pathology affects numerous systems, though the substantial loss of cholinergic neurons and α7 nicotinic receptors (α7AChR) is critical for the gradual cognitive decline. Aß binds to α7AChR under various experimental settings; nevertheless, the functional significance of this interaction is ambiguous. Whereas the capability of low Aß concentrations to activate α7AChR is functionally beneficial, extensive brain exposure to high Aß concentrations diminishes α7AChR activity, contributes to the cholinergic deficits that characterize AD. Aß and snake α-neurotoxins competitively bind to α7AChR. Accordingly, we designed a chemically modified α-cobratoxin (mToxin) to inhibit the interaction between Aß and α7AChR. Subsequently, we examined mToxin in a set of original in silico, in vitro, ex vivo experiments, and in a murine AD model. We report that mToxin reversibly inhibits α7AChR, though it attenuates Aß-induced synaptic transmission abnormalities, and upregulates pathways supporting long-term potentiation and reducing apoptosis. Remarkably, mToxin demonstrates no toxicity in brain slices and mice. Moreover, its chronic intracerebroventricular administration improves memory in AD-model animals. Our results point to unique mToxin neuroprotective properties, which might be tailored for the treatment of AD. Our methodology bridges the gaps in understanding Aß-α7AChR interaction and represents a promising direction for further investigations and clinical development.

Dysregulation of Cortical Neuron DNA Methylation Profile in Autism Spectrum Disorder.

Autism Spectrum Disorder (ASD) is a complex neuropsychiatric syndrome whose etiology includes genetic and environmental components. Since epigenetic marks are sensitive to environmental insult, they may be involved in the development of ASD. Initial brain studies have suggested a dysregulation of epigenetic marks in ASD. However, due to cellular heterogeneity in the brain, these studies have not determined if there is a true change in the neuronal epigenetic signature. Here, we report a genome-wide methylation study on fluorescence-activated cell sorting-sorted neuronal nuclei from the frontal cortex of 16 male ASD and 15 male control subjects. Using the 450 K BeadArray, we identified 58 differentially methylated regions (DMRs) that included loci associated to GABAergic system genes, particularly ABAT and GABBR1, and brain-specific MicroRNAs. Selected DMRs were validated by targeted Next Generation Bisulfite Sequencing. Weighted gene correlation network analysis detected 3 co-methylation modules which are significantly correlated to ASD that were enriched for genomic regions underlying neuronal, GABAergic, and immune system genes. Finally, we determined an overlap of the 58 ASD-related DMRs with neurodevelopment associated DMRs. This investigation identifies alterations in the DNA methylation pattern in ASD cortical neurons, providing further evidence that epigenetic alterations in disorder-relevant tissues may be involved in the biology of ASD.

Neuronal CTCF Is Necessary for Basal and Experience-Dependent Gene Regulation, Memory Formation, and Genomic Structure of BDNF and Arc.

CCCTC-binding factor (CTCF) is an organizer of higher-order chromatin structure and regulates gene expression. Genetic studies have implicated mutations in CTCF in intellectual disabilities. However, the role of CTCF-mediated chromatin structure in learning and memory is unclear. 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 thus suggests that CTCF-dependent gene expression regulation and genomic organization are regulators of learning and memory.

Hypomethylation of miR-142 promoter and upregulation of microRNAs that target the oxytocin receptor gene in the autism prefrontal cortex.

BACKGROUND: MicroRNAs are small RNA molecules that regulate the translation of protein from gene transcripts and are a powerful mechanism to regulate gene networks. Next-generation sequencing technologies have produced important insights into gene transcription changes that occur in the brain of individuals diagnosed with autism spectrum disorder (asd). However, these technologies have not yet been employed to uncover changes in microRNAs in the brain of individuals diagnosed with asd. METHODS: Small RNA next-generation sequencing was performed on RNA extracted from 12 human autism brain samples and 12 controls. Real-time PCR was used to validate a sample of the differentially expressed microRNAs, and bioinformatic analysis determined common pathways of gene targets. MicroRNA expression data was correlated to genome-wide DNA methylation data to determine if there is epigenetic regulation of dysregulated microRNAs in the autism brain. Luciferase assays, real-time PCR, and Western blot analysis were used to determine how dysregulated microRNAs may regulate the expression and translation of an autism-related gene transcript. RESULTS: We determined that miR-142-5p, miR-142-3p, miR-451a, miR-144-3p, and miR-21-5p are overexpressed in the asd brain. Furthermore, the promoter region of the miR-142 gene is hypomethylated in the same brain samples, suggesting that epigenetics plays a role in dysregulation of microRNAs in the brain. Bioinformatic analysis revealed that these microRNAs target genes that are involved in synaptic function. Further bioinformatic analysis, coupled with in vitro luciferase assays, determined that miR-451a and miR-21-5p can target the oxytocin receptor (OXTR) gene. OXTR gene expression is increased in these same brain samples, and there is a positive correlation between miR-21-5p and OXTR expression. However, miR-21-5p expression negatively correlates to production of OXTR protein from the OXTR transcript. Therefore, we suggest that miR-21-5p may attenuate OXTR expression in the human autism brain. CONCLUSIONS: Our data suggests that dysregulation of microRNAs may play a biological role in the brain of individuals of autism. In addition, we suggest an interaction between epigenetic mechanisms and microRNA dysregulation in the brain. Overall, this data adds an important link in our understanding of the molecular events that are dysregulated in the brain of individuals diagnosed with autism.