N ⁶ -methyladenosine (m ⁶ A) is the most abundant messenger RNA (mRNA) modification and plays crucial roles in diverse physiological processes. Using a massively parallel assay for m ⁶ A (MPm ⁶ A), we discover that m ⁶ A specificity is globally regulated by suppressors that prevent m ⁶ A deposition in unmethylated transcriptome regions. We identify exon junction complexes (EJCs) as m ⁶ A suppressors that protect exon junction–proximal RNA within coding sequences from methylation and regulate mRNA stability through m ⁶ A suppression. EJC suppression of m ⁶ A underlies multiple global characteristics of mRNA m ⁶ A specificity, with the local range of EJC protection sufficient to suppress m ⁶ A deposition in average-length internal exons but not in long internal and terminal exons. EJC-suppressed methylation sites colocalize with EJC-suppressed splice sites, which suggests that exon architecture broadly determines local mRNA accessibility to regulatory complexes.

Background: The BIN1 locus contains the second-most significant genetic risk factor for late-onset Alzheimer’s disease. BIN1 undergoes alternate splicing to generate tissue- and cell-type-specific BIN1 isoforms, which regulate membrane dynamics in a range of crucial cellular processes. Whilst the expression of BIN1 in the brain has been characterized in neurons and oligodendrocytes in detail, information regarding microglial BIN1 expression is mainly limited to large-scale transcriptomic and proteomic data. Notably, BIN1 protein expression and its functional roles in microglia, a cell type most relevant to Alzheimer’s disease, have not been examined in depth. Methods: Microglial BIN1 expression was analyzed by immunostaining mouse and human brain, as well as by immunoblot and RT-PCR assays of isolated microglia or human iPSC-derived microglial cells. Bin1 expression was ablated by siRNA knockdown in primary microglial cultures in vitro and Cre-lox mediated conditional deletion in adult mouse brain microglia in vivo. Regulation of neuroinflammatory microglial signatures by BIN1 in vitro and in vivo was characterized using NanoString gene panels and flow cytometry methods. The transcriptome data was explored by in silico pathway analysis and validated by complementary molecular approaches. Results: Here, we characterized microglial BIN1 expression in vitro and in vivo and ascertained microglia expressed BIN1 isoforms. By silencing Bin1 expression in primary microglial cultures, we demonstrate that BIN1 regulates the activation of proinflammatory and disease-associated responses in microglia as measured by gene expression and cytokine production. Our transcriptomic profiling revealed key homeostatic and lipopolysaccharide (LPS)-induced inflammatory response pathways, as well as transcription factors PU.1 and IRF1 that are regulated by BIN1. Microglia-specific Bin1 conditional knockout in vivo revealed novel roles of BIN1 in regulating the expression of disease-associated genes while counteracting CX3CR1 signaling. The consensus from in vitro and in vivo findings showed that loss of Bin1 impaired the ability of microglia to mount type 1 interferon responses to proinflammatory challenge, particularly the upregulation of a critical type 1 immune response gene, Ifitm3. Conclusions: Our convergent findings provide novel insights into microglial BIN1 function and demonstrate an essential role of microglial BIN1 in regulating brain inflammatory response and microglial phenotypic changes. Moreover, for the first time, our study shows a regulatory relationship between Bin1 and Ifitm3, two Alzheimer’s disease-related genes in microglia. The requirement for BIN1 to regulate Ifitm3 upregulation during inflammation has important implications for inflammatory responses during the pathogenesis and progression of many neurodegenerative diseases. Graphical

There is an increasing risk of mental disorders, such as acute stress disorder (ASD), post-traumatic stress disorder (PTSD) and depression among survivors who were trapped in rubble during earthquake. Such long-term impaction of a single acute restraint stress has not been extensively explored. In this study, we subjected mice to 24-hour-restraint to simulate the trapping episode, and investigated the acute (2 days after the restraint) and long-term (35 days after the restraint) impacts. Surprisingly, we found that the mice displayed depression-like behaviors, decreased glucose uptake in brain and reduced adult hippocampal neurogenesis 35 days after the restraint. Differential expression profiling based on microarrays suggested that genes and pathways related to depression and other mental disorders were differentially expressed in both PFC and hippocampus. Furthermore, the depression-like phenotypes induced by 24-hour-restraint could be reversed by fluoxetine, a type of antidepressant drug. These findings demonstrated that a single severe stressful event could produce long-term depressive-like phenotypes. Moreover, the 24-hour-restraint stress mice could also be used for further studies on mood disorders.

Epigenomic abnormalities caused by genetic mutation in epigenetic regulators can result in neurodevelopmental disorders, deficiency in neural plasticity and mental retardation. As a histone demethylase, plant homeodomain finger protein 8 (Phf8) is a candidate gene for syndromal and non-specific forms of X-chromosome-linked intellectual disability (XLID). Here we report that Phf8 knockout mice displayed impaired learning and memory, and impaired hippocampal long-term potentiation (LTP) without gross morphological defects. We also show that mTOR signaling pathway is hyperactive in hippocampus in Phf8 knockout mouse. Mechanistically, we show that demethylation of H4K20me1 by Phf8 results in transcriptional suppression of RSK1 and homeostasis of mTOR signaling. Pharmacological suppression of mTOR signaling with rapamycin in Phf8 knockout mice recovers the weakened LTP and cognitive deficits. Together, our results indicate that loss of Phf8 in animals causes deficient learning and memory by epigenetic disruption of mTOR signaling, and provides a potential therapeutic drug target to treat XLID.

Bridging integrator 1 (BIN1) is the second most prevalent genetic risk factor identified by genome-wide association studies (GWAS) for late-onset Alzheimer’s disease. BIN1 encodes an adaptor protein that regulates membrane dynamics in the context of endocytosis and neurotransmitter vesicle release. In vitro evidence suggests that BIN1 can directly bind to tau in the cytosol. In addition, BIN1’s function limits extracellular tau seed uptake by endocytosis and subsequent propagation as well as influences tau release through exosomes. However, the in vivo roles of BIN1 in tau pathogenesis and tauopathy-mediated neurodegeneration remain uncharacterized. We generated conditional knockout mice with a selective loss of Bin1 expression in the forebrain excitatory neurons and oligodendrocytes in P301S human tau transgenic background (line PS19). PS19 mice develop age-dependent tau neuropathology and motor deficits and are commonly used to study Alzheimer’s disease tau pathophysiology. The severity of motor deficits and neuropathology was compared between experimental and control mice that differ with respect to forebrain BIN1 expression. BIN1’s involvement in tau pathology and neuroinflammation was quantified by biochemical methods and immunostaining. Transcriptome changes were profiled by RNA-sequencing analysis to gain molecular insights. The loss of forebrain BIN1 expression in PS19 mice exacerbated tau pathology in the somatosensory cortex, thalamus, spinal cord and sciatic nerve, accelerated disease progression and caused early death. Intriguingly, the loss of BIN1 also mitigated tau neuropathology in select regions, including the hippocampus, entorhinal/piriform cortex, and amygdala, thus attenuating hippocampal synapse loss, neuronal death, neuroinflammation and brain atrophy. At the molecular level, the loss of forebrain BIN1 elicited complex neuronal and non-neuronal transcriptomic changes, including altered neuroinflammatory gene expression, concomitant with an impaired microglial transition towards the disease-associated microglial phenotype. These results provide crucial new information on in vivo BIN1 function in the context of tau pathogenesis. We conclude that forebrain neuronal BIN1 expression promotes hippocampal tau pathogenesis and neuroinflammation. Our findings highlight an exciting region specificity in neuronal BIN1 regulation of tau pathogenesis and reveal cell-autonomous and non-cell-autonomous mechanisms involved in BIN1 modulation of tau neuropathology.

Studies have indicated that depressive disorders are observed frequently in dentists. It’s suggested that dentists encounter numerous sources of stress in their professional career. We noticed that the noises in dental environments are very unpleasant. The animal modeling studies suggested that stressful noise could produce depressive-like phenotypes in rodent animals. We hypothesize that the dental noise may be one of the primary stressors causing depressive disorders in dentists. We treated C57BL/6 mice with programmatically played wide-spectrum dental noise for 8 h/day at 75 ± 10 dB SPL level for 30 days, and then tested the behaviors. After exposure to dental noise, animals displayed the depressive-like phenotypes, accompanied by inhibition of neurogenesis in hippocampus. These deficits were ameliorated by orally administered with antidepressant fluoxetine. Our results suggested that dental noise could be one of the primary stressors for the pathogenesis of depressive disorders and the dental noise mouse model could be used in further depression studies.