Overexpression of methyl-CpG-binding protein 2 and autoimmunity: evidence from MECP2 duplication syndrome, lupus, MECP2 transgenic and Mecp2 deficient mice

MECP2 duplication syndrome: Recent advances in pathophysiology and therapeutic perspectives

MECP2 duplication syndrome (MDS) is an X-linked neurodevelopmental disorder caused by duplication or extra copies of MECP2 gene. It primarily affects males and is characterized by intellectual disability, hypotonia, epilepsy, recurrent infections, and autistic features. Methyl-CpG binding protein 2 (MeCP2) encoded by MECP2 is a crucial epigenetic regulator of brain function. Expression levels are strictly regulated during brain development and maturation, and altered levels lead to severe neurodevelopmental disorders; excessive levels are associated with MDS, while insufficient levels cause Rett syndrome. This review provides a comprehensive overview of the recent advances in the pathophysiology and therapeutic perspectives of MDS, focusing on its pathophysiology, clinical features, disease models, and therapeutic strategies. Advances in studies using animal and patient-derived induced pluripotent stem cells (iPSCs)-derived neuronal models have provided insights into the molecular and cellular abnormalities associated with MDS and have facilitated therapeutic development. Among the emerging treatments, antisense oligonucleotide (ASO) therapy has gained significant attention as a promising approach for selectively suppressing MeCP2 overexpression. Preclinical studies using MDS mouse models and iPSCs-derived neurons have demonstrated that ASO treatment can partially restore neuronal abnormalities and clinical trials are currently underway.

Rare Turner syndrome and lupus coexistence with insights from DNA methylation patterns

Systemic lupus erythematosus (SLE or lupus) is a complex autoimmune disease that can affect multiple organs. While the exact disease etiology remains incompletely understood, there is a suggested influence of X-chromosome dosage in the pathogenesis of lupus. Here, we report a rare case of a female patient diagnosed with mosaic Turner syndrome and subsequently presenting with juvenile-onset SLE. DNA methylation patterns were analyzed in this patient and compared with age-matched female SLE controls, revealing higher methylation levels in interferon-regulated genes previously shown to be hypomethylated in SLE. These data provide a potential link between a gene-dose effect from the X-chromosome and the lupus-defining epigenotype. We hypothesize that the attenuated demethylation in interferon-regulated genes might provide a protective effect explaining the rarity of SLE in Turner syndrome.

A brief history of MECP2 duplication syndrome: 20-years of clinical understanding

MECP2 duplication syndrome (MDS) is a rare, X-linked, neurodevelopmental disorder caused by a duplication of the methyl-CpG-binding protein 2 (MECP2) gene-a gene in which loss-of-function mutations lead to Rett syndrome (RTT). MDS has an estimated live birth prevalence in males of 1/150,000. The key features of MDS include intellectual disability, developmental delay, hypotonia, seizures, recurrent respiratory infections, gastrointestinal problems, behavioural features of autism and dysmorphic features-although these comorbidities are not yet understood with sufficient granularity. This review has covered the past two decades of MDS case studies and series since the discovery of the disorder in 1999. After comprehensively reviewing the reported characteristics, this review has identified areas of limited knowledge that we recommend may be addressed by better phenotyping this disorder through an international data collection. This endeavour would also serve to delineate the clinical overlap between MDS and RTT.

Comparative Analysis of Global Proteome and Lysine Acetylome Between Naive CD4+ T Cells and CD4+ T Follicular Helper Cells

As a subgroup of CD4⁺ T helper cells, follicular helper T (Tfh) cells provide help to germinal center B cells and mediate the development of long-lived humoral immunity. Dysregulation of Tfh cells is associated with several major autoimmune diseases. Although recent studies showed that Tfh cell differentiation is controlled by the transcription factor Bcl6, cytokines, and cell-cell signals, limited information is available on the proteome and post-translational modifications (PTMs) of proteins in human Tfh cells. In the present study, we investigated quantitative proteome and acetylome in human naive CD4⁺ T cells and in vitro induced Tfh (iTfh) cells using the tandem mass tag (TMT) labeling technique, antibody-based affinity enrichment, and high-resolution liquid chromatography-mass spectrometry (LC-MS)/mass spectrometry (MS) analysis. In total, we identified 802 upregulated proteins and 598 downregulated proteins at the threshold of 1.5-fold in iTfh cells compared to naive CD4⁺ T cells. With the aid of intensive bioinformatics, the biological process, the cellular compartment, the molecular function, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, and protein–protein interaction of these differentially expressed proteins were revealed. Moreover, the acetylome data showed that 22 lysine (K) acetylated proteins are upregulated and 26 K acetylated proteins are downregulated in iTfh cells compared to the naive CD4⁺ T cells, among which 11 differentially acetylated K residues in core histones were identified, indicating that protein acetylation and epigenetic mechanism are involved in regulating Tfh cell differentiation. The study provides some important clues for investigating T cell activation and Tfh cell differentiation.

Effect of Jieduquyuziyin prescription-treated rat serum on MeCP2 gene expression in Jurkat T cells

How genomic DNA methylation and methyl CpG-binding protein 2 (MeCP2) gene expression affect the pathogenesis of systemic lupus erythematosus (SLE) remains poorly understood. Traditional Chinese medicine has a unique effect in the treatment of SLE patients. This study aimed to investigate the effect of Jieduquyuziyin prescription (JP)-treated rat serum on the gene expression of MeCP2 in Jurkat T cells and its role in the pathogenesis of SLE. Jurkat T cells were harvested, and drug-containing serum was prepared. The ferulic acid and paeoniflorin content in the drug-containing serum were determined by liquid chromatography-mass spectrometry (LC-MS/MS). 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assays were used to screen the optimal concentration of drug-containing serum. The DNA methylation level in Jurkat T cells was detected with a Methylamp™ Total DNA Methylation Kit. The methylation status of the MeCP2 promoter region was detected using bisulfite modification and methylation-specific PCR (MSP). Real-time PCR was used to measure MeCP2 mRNA expression. Western blotting and flow cytometry were done to detect MeCP2 protein expression in Jurkat cell nuclei. Paeoniflorin and ferulic acid were detected in the drug-containing serum of JP-treated rats. The results showed that cell growth was affected in the high serum-containing drug group. The experimental results showed that JP and prednisone acetate increased the level of genomic DNA methylation and MeCP2 gene promoter region methylation in Jurkat cells. MeCP2 mRNA and protein levels were also increased in the JP and prednisone acetate groups. Furthermore, flow cytometry revealed that the expression of MeCP2 protein in Jurkat T cell nuclei was higher in the drug group than the blank control group, and these results were consistent with the western blot analysis results. Our study found that there is a negative correlation between drug-containing serum and cell survival rate. JP upregulated the levels of DNA methylation, MeCP2 mRNA and protein as effectively as prednisone acetate and thus may activate the MeCP2 gene by increasing the methylation level, thereby inhibiting the pathogenesis of SLE. Therefore, JP may potentially be used to treat SLE patients. The Jurkat T lymphocyte in vitro experiments provided a foundation to study the effects of JP on the lupus mouse CD4⁺ T cell methylation mechanism and to further explore the pathogenesis of SLE.

Methyl-CpG-binding protein 2 mediates antifibrotic effects in scleroderma fibroblasts

OBJECTIVE

Emerging evidence supports a role for epigenetic regulation in the pathogenesis of scleroderma (SSc). We aimed to assess the role of methyl-CpG-binding protein 2 (MeCP2), a key epigenetic regulator, in fibroblast activation and fibrosis in SSc.

METHODS

Dermal fibroblasts were isolated from patients with diffuse cutaneous SSc (dcSSc) and from healthy controls. MeCP2 expression was measured by qPCR and western blot. Myofibroblast differentiation was evaluated by gel contraction assay in vitro. Fibroblast proliferation was analysed by ki67 immunofluorescence staining. A wound healing assay in vitro was used to determine fibroblast migration rates. RNA-seq was performed with and without MeCP2 knockdown in dcSSc to identify MeCP2-regulated genes. The expression of MeCP2 and its targets were modulated by siRNA or plasmid. Chromatin immunoprecipitation followed by sequencing (ChIP-seq) using anti-MeCP2 antibody was performed to assess MeCP2 binding sites within MeCP2-regulated genes.

RESULTS

Elevated expression of MeCP2 was detected in dcSSc fibroblasts compared with normal fibroblasts. Overexpressing MeCP2 in normal fibroblasts suppressed myofibroblast differentiation, fibroblast proliferation and fibroblast migration. RNA-seq in MeCP2-deficient dcSSc fibroblasts identified MeCP2-regulated genes involved in fibrosis, including PLAU, NID2 and ADA. Plasminogen activator urokinase (PLAU) overexpression in dcSSc fibroblasts reduced myofibroblast differentiation and fibroblast migration, while nidogen-2 (NID2) knockdown promoted myofibroblast differentiation and fibroblast migration. Adenosine deaminase (ADA) depletion in dcSSc fibroblasts inhibited cell migration rates. Taken together, antifibrotic effects of MeCP2 were mediated, at least partly, through modulating PLAU, NID2 and ADA. ChIP-seq further showed that MeCP2 directly binds regulatory sequences in NID2 and PLAU gene loci.

CONCLUSIONS

This study demonstrates a novel role for MeCP2 in skin fibrosis and identifies MeCP2-regulated genes associated with fibroblast migration, myofibroblast differentiation and extracellular matrix degradation, which can be potentially targeted for therapy in SSc.

MECP2 duplication syndrome in a Chinese family

Background

Methyl-CpG-binding protein 2 (MeCP2) is a key transcriptional regulator of gene expression in the maintenance and development of the central nervous system. Loss- or gain-function of this gene may contribute to neurodevelopmental disorders. The aim of this study is to delineate the clinical characteristics of MECP2 duplication syndrome and the hereditary mechanism in a Chinese family.

Case presentation

We identified a Chinese family with three persons carry MECP2 gene duplication: a boy, his mother and his grandmother. The duplication segment which was detected by multiplex ligation-dependent probe amplification (MLPA) included gene MECP2, interleukin-1 receptor-associated kinase 1 (IRAK1), filamin A (FLNA), and L1 cell adhesion molecule (L1CAM). Furthermore, array comparative genomic hybridization (aCGH) was performed on the mother, showed that MECP2 containing duplication was 510 Kb (153,113,885-153,624,154), including 16 other genes except MECP2. The boy showed most symptoms of MECP2 duplication syndrome. His mother and maternal grandmother were asymptomatic. Both female carriers had a skewed X chromosome inactivation (XCI), which were 80:20 and 74:26 respectively.

Conclusion

To our knowledge, this is the second reported Chinese Han family with MECP2-containing duplications. And this patient had recurrent respiratory infections which was different from the first two Chinese-brother cases. MECP2 is the core gene responsible for MECP2 duplication syndrome. XCI may play an important role in modulating the clinical manifestation.

Epigenetics and autoimmune diseases: the X chromosome-nucleolus nexus

Autoimmune diseases occur more often in females, suggesting a key role for the X chromosome. X chromosome inactivation, a major epigenetic feature in female cells that provides dosage compensation of X-linked genes to avoid overexpression, presents special vulnerabilities that can contribute to the disease process. Disruption of X inactivation can result in loss of dosage compensation with expression from previously sequestered genes, imbalance of gene products, and altered endogenous material out of normal epigenetic context. In addition, the human X has significant differences compared to other species and these differences can contribute to the frequency and intensity of the autoimmune disease in humans as well as the types of autoantigens encountered. Here a link is demonstrated between autoimmune diseases, such as systemic lupus erythematosus, and the X chromosome by discussing cases in which typically non-autoimmune disorders complicated with X chromosome abnormalities also present lupus-like symptoms. The discussion is then extended to the reported spatial and temporal associations of the inactive X chromosome with the nucleolus. When frequent episodes of cellular stress occur, the inactive X chromosome may be disrupted and inadvertently become involved in the nucleolar stress response. Development of autoantigens, many of which are at least transiently components of the nucleolus, is then described. Polyamines, which aid in nucleoprotein complex assembly in the nucleolus, increase further during cell stress, and appear to have an important role in the autoimmune disease process. Autoantigenic endogenous material can potentially be stabilized by polyamines. This presents a new paradigm for autoimmune diseases: that many are antigen-driven and the autoantigens originate from altered endogenous material due to episodes of cellular stress that disrupt epigenetic control. This suggests that epigenetics and the X chromosome are important aspects of autoimmune diseases.

DNA modifications: function and applications in normal and disease States

Epigenetics refers to a variety of processes that have heritable effects on gene expression programs without changes in DNA sequence. Key players in epigenetic control are chemical modifications to DNA, histone, and non-histone chromosomal proteins, which establish a complex regulatory network that controls genome function. Methylation of DNA at the fifth position of cytosine in CpG dinucleotides (5-methylcytosine, 5mC), which is carried out by DNA methyltransferases, is commonly associated with gene silencing. However, high resolution mapping of DNA methylation has revealed that 5mC is enriched in exonic nucleosomes and at intron-exon junctions, suggesting a role of DNA methylation in the relationship between elongation and RNA splicing. Recent studies have increased our knowledge of another modification of DNA, 5-hydroxymethylcytosine (5hmC), which is a product of the ten-eleven translocation (TET) proteins converting 5mC to 5hmC. In this review, we will highlight current studies on the role of 5mC and 5hmC in regulating gene expression (using some aspects of brain development as examples). Further the roles of these modifications in detection of pathological states (type 2 diabetes, Rett syndrome, fetal alcohol spectrum disorders and teratogen exposure) will be discussed.