MEF2C hypofunction in neuronal and neuroimmune populations produces MEF2C haploinsufficiency syndrome behaviors in mice
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ABSTRACT: Microdeletions of the MEF2C gene are linked to a syndromic form of autism termed MEF2C haploinsufficiency syndrome (MCHS). Here, we show that MCHS-associated missense mutations cluster in the conserved DNA binding domain and disrupt MEF2C DNA binding. DNA binding-deficient global Mef2c heterozygous mice (Mef2c-Het) display numerous MCHS-like behaviors, including autism-related behaviors, as well as deficits in cortical excitatory synaptic transmission. We find that hundreds of genes are dysregulated in Mef2c-Het cortex, including significant enrichments of autism risk and excitatory neuron genes. In addition, we observe an enrichment of upregulated microglial genes, but not due to neuroinflammation in the Mef2c-Het cortex. Importantly, conditional Mef2c heterozygosity in forebrain excitatory neurons reproduces a subset of the Mef2c-Het phenotypes, while conditional Mef2c heterozygosity in microglia reproduces social deficits and repetitive behavior. Together our findings suggest that MEF2C regulates typical brain development and function through multiple cell types, including excitatory neuronal and neuroimmune populations.
Project description:Numerous genetic variants associated with MEF2C are linked to autism, intellectual disability (ID) and schizophrenia (SCZ) – a heterogeneous collection of neurodevelopmental disorders with unclear pathophysiology. MEF2C is highly expressed in developing cortical excitatory neurons, but its role in their development remains unclear. We show here that conditional embryonic deletion of Mef2c in cortical and hippocampal excitatory neurons (Emx1-lineage) produces a dramatic reduction in cortical network activity in vivo, due in part to a dramatic increase in inhibitory and a decrease in excitatory synaptic transmission. In addition, we find that MEF2C regulates E/I synapse density predominantly as a cell-autonomous, transcriptional repressor. Analysis of differential gene expression in Mef2c mutant cortex identified a significant overlap with numerous synapse- and autism-linked genes, and the Mef2c mutant mice displayed numerous behaviors reminiscent of autism, ID and SCZ, suggesting that perturbing MEF2C function in neocortex can produce autistic- and ID-like behaviors in mice.
Project description:Recent studies revealed that microdeletion of human chromosome 5q14.3 leads to the occurrence of neurodevelopmental disorders such as autism and intellectual disability, and have identified Mef2c haploinsufficiency as a main cause. Here, we found that a brain-enriched long non-coding RNA, termed NDIME, is located near the Mef2c locus and is required for normal neural differentiation of mouse embryonic stem cells (mESCs). Mechanistic studies showed that exons 1-3 of NDIME interacts with the major component of polycomb repressive complex 2 (PRC2) EZH2, blocking EZH2-mediated trimethylation of histone H3 lysine 27 (H3K27me3) at the Mef2c promoter, ensuring Mef2c transcription. Moreover, both the expression levels of NDIME and Mef2c were significantly downregulated in the hippocampus of autism model mice, while adeno-associated virus (AAV)-mediated expression of NDIME significantly increased the Mef2c expression and ameliorated autism-like behaviors. Collectively, our findings reveal an epigenetic mechanism of NDIME regulating Mef2c transcription and neural differentiation, and the potential effects and application of the NDIME/Mef2c axis in autism.
Project description:Gene expression of Mef2c-het mice vs. WT littermates in hippocampus Total RNA isolated from hippocampus of P1 and P30 aged Mef2c-HET and WT mice using QIAGEN miRNeasy mini kit (QIAGEN; Cat #217004) were processed on an Illumina mouse Ref8 v2 beadchip microarrays following the manufacture’s protocol. Microarray data analysis was performed using R and Bioconductor packages. Raw expression data were log2 transformed and normalized by quantile normalization. Probes were considered robustly expressed if the detection P value was 0.01 for at least half of the samples in the data set.
Project description:We have performed conditional inactivation of mef2c in the anterior heart field (AHF) of mice and observed a phenotypic spectrum of outflow tract anomalies in the conditional mutant hearts. In an effort to identify misregulated genes in the outflow tracts of the mutants, we have performed RNA-Seq on outflow tract samples dissected from E10.5 mutant and wild-type embryos. There are four wild-type samples and four mutant samples.
Project description:MDGA2 is an excitatory synaptic suppressor and its mutations have been associated with autism spectrum disorder (ASD). However, the detailed physiological function of MDGA2 and the mechanism underlying MDGA2 deficiency-caused ASD has yet to be elucidated. Herein, we not only confirm that Mdga2+/- mice exhibit increased excitatory synapse transmission and ASD-like behaviors, but also identify aberrant BDNF/TrkB signaling activation in these mice. We demonstrate that MDGA2 interacts with TrkB through its MAM domain, thereby competing the binding of BDNF to TrkB. Both loss of MDGA2 and the ASD-associated MDGA2 V930I mutation promote the BDNF/TrkB signaling activity. Importantly, we demonstrate that inhibiting the BDNF/TrkB signaling by both small molecular compound and MDGA2-derived peptide can attenuate the increase of AMPA receptor-mediated excitatory synaptic activity and social deficits in MDGA2 deficient mice. These results highlight a novel MDGA2-BDNF/TrkB-dependent mechanism underlying the synaptic function regulation, which may become a therapeutic target for ASD.
Project description:Pharmacological inhibition of cGAS with TDI-6570 protected against the synaptic loss and cognitive deficits in P301S tauopathy model, likely via enhancing MEF2C transcriptional network and associated cognitive resilience
Project description:We have performed conditional inactivation of mef2c in the anterior heart field (AHF) of mice and observed a phenotypic spectrum of outflow tract anomalies in the conditional mutant hearts. In an effort to identify misregulated genes in the outflow tracts of the mutants, we have performed RNA-Seq on outflow tract samples dissected from E10.5 mutant and wild-type embryos.
Project description:Acute myelogenous leukemia (AML) is driven by leukemic stem cells (LSC) generated by mutations that confer (or maintain) self-renewal potential coupled to an aberrant differentiation program. Using retroviral mutagenesis, we identified genes that generate LSC in collaboration with genetic disruption of the gene encoding interferon response factor 8 (Irf8), which induces a myeloproliferation in vivo. Amongst the targeted genes, we identified Mef2c, encoding a MADS transcription factor, and confirmed that over-expression induced a myelomonocytic leukemia in cooperation with Irf8 deficiency. Strikingly, several of the genes identified in our screen have been reported to be upregulated in the mixed-lineage leukemia (MLL) subtype. High MEF2C expression levels were confirmed in AML patient samples with MLL gene disruptions, prompting an investigation of the causal interplay. Using a conditional mouse strain, we demonstrated that Mef2c deficiency does not impair the establishment nor maintenance of LSC generated in vitro by MLL/ENL fusion proteins â?? however, its loss led to compromised homing and invasiveness of the tumor cells. Mef2c-dependent targets included several genes encoding matrix metalloproteinases and chemokine ligands and receptors, providing a mechanistic link to increased homing and motility. Thus an early event in LSC generation may be responsible for the aggressive nature of this leukemia subtype. Experiment Overall Design: For gene expression profiling of M/E cells, RNA was isolated from M/E-Mef2c del/- cells infected with MYs-iPAC (empty vector) or MYs-pMef2cASR after puromycin selection at three different time points, pooled, and hybridized against the Agilent Whole Mouse Genome Microarray 4x44K using the one-color service of Miltenyi. Transcript levels were verified by real-time RT-PCR using the SYBRGreen Reaction Mix (Roche Mannheim) in a Roche Light-Cycler. cDNA levels were normalized against Hprt transcript levels. Primers and amplification conditions are available upon request.
Project description:The Mef2 family transcriptional regulator Mef2c is highly expressed in maturing bone marrow and peripheral mature B cells. To evaluate the role of this transcription factor in B cell development, we generated a B cell specific conditional deletion of Mef2c using the Mb-1-Cre transgene that is expressed during the early stages of immunoglobulin rearrangement. Young mice possessing this defect demonstrated a significant impairment in B cell numbers in bone marrow and spleen. This phenotype was evident in all B cell subsets; however, as the animals mature, the deficit in the peripheral mature B cell compartments was overcome. The absence of Mef2c in mature B cells led to unique CD23+ and CD23- subsets that were evident in Mef2c KO primary samples as well as cultured, differentiated B cells but not in WT cell populations. Genome wide expression analysis of immature and mature B cells lacking Mef2c indicated altered expression for a number of key regulatory proteins for B cell function including Ciita, CD23, Cr1/Cr2, and Tnfsf4. Chromatin immunoprecipitation analysis confirmed Mef2c binding to the promoters of these genes indicating a direct link between the presence (or absence) of Mef2c and altered transcriptional control in mature B cells. Four samples are submitted.