Project description:The transcription factors MEF2C, GATA4, and TBX5 (MGT) are well established for converting fibroblasts into induced cardiomyocytes (iCMs). However, these reprogramming factors contain effector domains, yet their functional roles in cardiac reprogramming remain largely uncharacterized. Furthermore, whether internal deletions of these domains improve or compromise reprogramming efficiency has not been elucidated. Here we found that the combination of MEF2C and GATA4 mutants (MΔGΔT) elevated reprogramming efficiency by 7-fold to ~21%, achieving robust induction of iCMs with well-defined sarcomeric structures.
Project description:Cardiac transcription factors (TFs) directly reprogram fibroblasts into induced cardiomyocytes (iCMs), where Mef2c acts as a pioneer factor with Gata4 and Tbx5 (GT). However, generation of functional and mature iCMs is inefficient and molecular mechanisms underlying this process remains largely unknown. Here we found that transduction of transcriptionally activated Mef2c via fusion of the powerful MyoD transactivation domain increased generation of beating iCMs by 30-fold in combination with GT.
Project description:Direct cardiac reprogramming converts fibroblasts into induced cardiomyocytes (iCMs) with the minimal combination of transcription factors, Gata4 (G), Mef2c (M), and Tbx5 (T). However, the induction of functional mature iCMs is inefficient and the mechanisms remain elusive. Mef2c is a central transcription factor in direct cardiac reprogramming. We investigated the effect of Mef2c isoforms(M1, M2, M6) and transcriptional activity (M2TAD) on cardiac reprogramming on cardiac reprogramming. Then, we found that the active form of Mef2c evoked epigenetic remodeling cooperating with p300 and promoted the maturation of iCMs.
Project description:Direct reprogramming of fibroblasts into cardiomyocytes (CMs) represents a promising strategy to regenerate CMs lost after ischemic heart injury. Overexpression of GATA4, HAND2, MEF2C, TBX5, miR-1, and miR-133 (GHMT2m) along with transforming growth factor beta (TGFbeta) inhibition efficiently promotes reprogramming. However, the mechanisms by which TGFbeta; blockade promotes cardiac reprogramming remain unknown. Here, we identify interactions between the histone H3 lysine 27 trimethylation (H3K27me3), demethylase JMJD3, the SWI/SNF remodeling complex subunit BRG1, and cardiac transcription factors. Furthermore, canonical TGFbeta; signaling regulates the interaction between GATA4 and JMJD3. TGF-beta; activation impairs the ability of GATA4 to bind target genes and prevents demethylation of H3K27 at cardiac gene promoters during cardiac reprogramming. Finally, a mutation in GATA4 (V267M) exhibits reduced binding to JMJD3 and impaired cardiomyogenesis. Thus, we have identified an epigenetic mechanism wherein canonical TGFbeta; pathway activation impairs cardiac gene programming by interfering with GATA4-JMJD3 interactions.
Project description:The mammalian RNA-binding protein AUF1 (AU-binding factor 1, also known as heterogeneous nuclear ribonucleoprotein D, hnRNP D) binds to numerous mRNAs and influences their post-transcriptional fate. Given that many AUF1 target mRNAs encode muscle-specific factors, we investigated the function of AUF1 in skeletal muscle differentiation. In mouse C2C12 myocytes, where AUF1 levels rise at the onset of myogenesis and remain elevated throughout myocyte differentiation into myotubes, RIP (RNP immunoprecipitation) analysis indicated that AUF1 binds prominently to Mef2c (myocyte enhancer factor 2c) mRNA, which encodes the key myogenic transcription factor Mef2c. By performing mRNA half-life measurements and polysome distribution analysis, we found that AUF1 associated with the 3’UTR of Mef2c mRNA and promoted Mef2c translation without affecting Mef2c mRNA stability. In addition, AUF1 promoted Mef2c gene transcription via a lesser-known role of AUF1 in transcriptional regulation. Importantly, lowering AUF1 delayed myogenesis, while ectopically restoring Mef2c expression levels partially rescued the impairment of myogenesis seen after reducing AUF1 levels. We propose that Mef2c is a key effector of the myogenesis program promoted by AUF1. Keywords: ribonucleoprotein complex; post-transcriptional gene regulation; muscle cell differentiation; myocytes; mRNA translation; mRNA stability; post-transcriptional gene regulation; transcriptome
Project description: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:Vibrio vulnificus is an foodborne pathogen that can cause gastroenteritis and septicemia in humans. V. vulnificus secretes a multifunctional autoprocessing repeats-in-toxin (MARTX) toxin as an essential virulence factor to cause disease. MARTX toxins are pore-forming toxins that translocate multiple functionally independent effector domains into a target cell. MARTX toxins of V. vulnificus can contain anywhere from 3 to 5 of the 10 identified effector domains and strains with different effector repertories having varying virulence potential. The goal of this study was to compare how different effector combinations from an F-type MARTX toxin differentially remodel the transcriptional response of human intestinal epithelial cells (IECs). F-type MARTX toxins contain five effector domains – the actin crosslinking domain (ACD), two copies the makes caterpillar floppy-like domain (MCF), and alpha-beta hydrolase (ABH) domain, and the Ras/Rap1 specific endopeptidase (RRSP). Cultured human IECs were treated with V. vulnificus or strains modified to secrete a toxin with only ACD, ACD with MCF-ABH, ACD with RRSP, or no active effectors. We demonstrate that when no active effectors are present, the bacterium induces minimal changes in the transcriptional profile of IECs. However, the strains containing different effector combinations each uniquely remodeled the transcriptional profile of IECs. These data provide insight into how V. vulnificus strains with varying effector combinations can differentially regulate the host cell response to cause disease.
Project description:In acute myeloid leukemia, chemotherapy resistance remains prevalent and poorly understood. Using functional proteomics of patient AML specimens, we identified MEF2C S222 phosphorylation as a specific marker of primary chemoresistance. We found that transgenic Mef2cS222A/S222A mice engineered to block MEF2C phosphorylation exhibited normal hematopoiesis, but were resistant to leukemogenesis induced by MLL-AF9. MEF2C phosphorylation was required for leukemia stem cell maintenance, induced by MARK kinases in cells, and blocked by selective MARK inhibitor MRT199665, which caused apoptosis of MEF2C-activated human AML cell lines and primary patient specimens, but not those lacking MEF2C. These findings identify signaling-dependent dysregulation of transcription factor control as a determinant of therapy response in AML, with immediate potential for improved diagnosis and therapy for this disease.
Project description:The mammalian RNA-binding protein AUF1 (AU-binding factor 1, also known as heterogeneous nuclear ribonucleoprotein D, hnRNP D) binds to numerous mRNAs and influences their post-transcriptional fate. Given that many AUF1 target mRNAs encode muscle-specific factors, we investigated the function of AUF1 in skeletal muscle differentiation. In mouse C2C12 myocytes, where AUF1 levels rise at the onset of myogenesis and remain elevated throughout myocyte differentiation into myotubes, RIP (RNP immunoprecipitation) analysis indicated that AUF1 binds prominently to Mef2c (myocyte enhancer factor 2c) mRNA, which encodes the key myogenic transcription factor Mef2c. By performing mRNA half-life measurements and polysome distribution analysis, we found that AUF1 associated with the 3M-bM-^@M-^YUTR of Mef2c mRNA and promoted Mef2c translation without affecting Mef2c mRNA stability. In addition, AUF1 promoted Mef2c gene transcription via a lesser-known role of AUF1 in transcriptional regulation. Importantly, lowering AUF1 delayed myogenesis, while ectopically restoring Mef2c expression levels partially rescued the impairment of myogenesis seen after reducing AUF1 levels. We propose that Mef2c is a key effector of the myogenesis program promoted by AUF1. Keywords: ribonucleoprotein complex; post-transcriptional gene regulation; muscle cell differentiation; myocytes; mRNA translation; mRNA stability; post-transcriptional gene regulation; transcriptome C2C12 mouse myoblasts were cultured in Dulbecco's modified Eagle's medium (DMEM; Invitrogen, Carlsbad, CA, USA) supplemented with 10% serum (Invitrogen) and antibiotics (Invitrogen). Differentiation was induced on sub-confluent cultures by replacing the growth media (GM, DMEM with 10% FBS) with differentiation media (DM, DMEM with 2% horse serum). At various time points after differentiation, cells were harvested and RNA was extracted with phenol-chloroform and either saved as input samples for microarrys or subjected to AUF1 or IgG ribonucleoprotein immunoprecipitation. C2C12 cells cultured in GM and DM were lysed in 20 mM Tris-HCl at pH 7.5, 100 mM KCl, 5 mM MgCl2, and 0.5% NP-40 for 10 min on ice and centrifuged at 15,000 M-CM-^W g for 10 min at 4M-BM-0C. The supernatants were incubated with protein-A Dynabeads beads coated with anti-AUF1 (Millipore) or with control IgG (Santa Cruz Biotechnology) antibodies for 2 hr at 4M-BM-0C. The beads were washed with NT2 buffer (50 mM Tris-HCl [pH 7.5], 150 mM NaCl, 1 mM MgCl2, 0.05% NP-40), followed by incubation with 20 units of RNase-free DNase I for 15 min at 37M-BM-0C to remove the DNA. The samples were then incubated for 15 min at 55M-BM-0C with 0.1% SDS/0.5 mg/ml Proteinase K to digest proteins. The RNA from the IP samples was extracted using phenol-chloroform, precipitated, and used along with the RNA from the input samples for cDNA microarrays.