Co-methylation analyses identify CpGs associated with lipid traits in Chinese discordant monozygotic twins.

To control genetic background and early life milieu in genome-wide DNA methylation analysis for blood lipids, we recruited Chinese discordant monozygotic twins to explore the relationships between DNA methylations and total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TG). 132 monozygotic (MZ) twins were included with discordant lipid levels and completed data. A linear mixed model was conducted in Epigenome-wide association study (EWAS). Generalized estimating equation model was for gene expression analysis. We conducted Weighted correlation network analysis (WGCNA) to build co-methylated interconnected network. Additional Qingdao citizens were recruited for validation. Inference about Causation through Examination of Familial Confounding (ICE FALCON) was used to infer the possible direction of these relationships. A total of 476 top CpGs reached suggestively significant level (P < 10-4), of which, 192 CpGs were significantly associated with TG (FDR < 0.05). They were used to build interconnected network and highlight crucial genes from WGCNA. Finally, four CpGs in GATA4 were validated as risk factors for TC; six CpGs at ITFG2-AS1 were negatively associated with TG; two CpGs in PLXND1 played protective roles in HDL-C. ICE FALCON indicated abnormal TC was regarded as the consequence of DNA methylation in CpGs at GATA4, rather than vice versa. Four CpGs in ITFG2-AS1 were both causes and consequences of modified TG levels. Our results indicated that DNA methylation levels of 12 CpGs in GATA4, ITFG2-AS1, and PLXND1 were relevant to TC, TG, and HDL-C, respectively, which might provide new epigenetic insights into potential clinical treatment of dyslipidemia.

First report on female monozygotic twins discordant for congenital nephrogenic diabetes insipidus.

Ninety percent of congenital nephrogenic diabetes insipidus (NDI) are X-linked inherited and are caused by mutations in the vasopressin type 2 receptor gene (AVPR2). Most affected individuals are males. Only sporadic female cases have been reported. Here, we first reported a female monozygotic twin with discordant phenotypes for NDI carrying a missense variant c.845T>C (p.Leu282Pro) in exon 4 of AVPR2. Intracellular cAMP concentrations in COS7 cells transfected with AVPR2-L282P were significantly decreased by about 60% compared with those in wild-type AVPR2 plasmid transfected cells, suggesting this variation was pathogenic. The X-inactivation pattern was investigated in peripheral leukocytes and urine sediments in both the unaffected and affected pair. Results showed that the affected pair had a skewed X chromosome inactivation (XCI) pattern in urine sediments and a random XCI pattern in leukocytes, while the unaffected pair showed a random XCI pattern both in leukocytes and urine sediments. This was the first report of monozygotic twins who developed different phenotypes of NDI. Our study suggested that the development of NDI symptoms is more closely associated with the XCI pattern in urine sediments compared with the XCI pattern in peripheral leukocytes. Analysis of XCI in peripheral leukocytes may not be enough to explore possible mechanisms.

Metabolomics efficiently discriminates monozygotic twins in peripheral blood.

Monozygotic (MZ) twins cannot be distinguished using conventional forensic STR typing because they present identical STR genotypings. However, MZ twins do not always live in the same environment and often have different dietary and other lifestyle habits. Metabolic profiles are deyermined by individual characteristics and are also influenced by the environment in which they live. Therefore, they are potential markers capable of identifying MZ twins. Moreover, the production of proteins varies from organism to organism and is influenced by both the physiological state of the body and the external environment. Hence, we used metabolomics and proteomics to identify metabolites and proteins in peripheral blood to discriminate MZ twins. We identified 1749 known metabolites and 622 proteins in proteomic analysis. The metabolic profiles of four pairs of MZ twins revealed minor differences in intra-MZ twins and major differences in inter-MZ twins. Each pair of MZ twins exhibited distinct characteristics, and four metabolites-methyl picolinate, acesulfame, paraxanthine, and phenylbenzimidazole sulfonic acid-were observed in all four MZ twin pairs. These four differential exogenous metabolites conincidently show that the different external environments and life styles can be well distinguished by metabolites, considering that twins do not all have the same eating habits and living environments. Moreover, MZ twins showed different protein profiles in serum but not in whole blood. Thus, our results indicate that differential metabolites provide potential biomarkers for the personal identification of MZ twins in forensic medicine.

Technical strategy for monozygotic twin discrimination by single-nucleotide variants.

Monozygotic (MZ) twins are theoretically genetically identical. Although they are revealed to accumulate mutations after the zygote splits, discriminating between twin genomes remains a formidable challenge in the field of forensic genetics. Single-nucleotide variants (SNVs) are responsible for a substantial portion of genetic variation, thus potentially serving as promising biomarkers for the identification of MZ twins. In this study, we sequenced the whole genome of a pair of female MZ twins when they were 27 and 33 years old to approximately 30 × coverage using peripheral blood on an Illumina NovaSeq 6000 Sequencing System. Potentially discordant SNVs supported by whole-genome sequencing were validated extensively by amplicon-based targeted deep sequencing and Sanger sequencing. In total, we found nine bona fide post-twinning SNVs, all of which were identified in the younger genomes and found in the older genomes. None of the SNVs occurred within coding exons, three of which were observed in introns, supported by whole-exome sequencing results. A double-blind test was employed, and the reliability of MZ twin discrimination by discordant SNVs was endorsed. All SNVs were successfully detected when input DNA amounts decreased to 0.25 ng, and reliable detection was limited to seven SNVs below 0.075 ng input. This comprehensive analysis confirms that SNVs could serve as cost-effective biomarkers for MZ twin discrimination.

Research progress and potential application of microRNA and other non-coding RNAs in forensic medicine.

At present, epigenetic markers have been extensively studied in various fields and have a high value in forensic medicine due to their unique mode of inheritance, which does not involve DNA sequence alterations. As an epigenetic phenomenon that plays an important role in gene expression, non-coding RNAs (ncRNAs) act as key factors mediating gene silencing, participating in cell division, and regulating immune response and other important biological processes. With the development of molecular biology, genetics, bioinformatics, and next-generation sequencing (NGS) technology, ncRNAs such as microRNA (miRNA), circular RNA (circRNA), long non-coding RNA (lncRNA), and P-element induced wimpy testis (PIWI)-interacting RNA (piRNA) are increasingly been shown to have potential in the practice of forensic medicine. NcRNAs, mainly miRNA, may provide new strategies and methods for the identification of tissues and body fluids, cause-of-death analysis, time-related estimation, age estimation, and the identification of monozygotic twins. In this review, we describe the research progress and application status of ncRNAs, mainly miRNA, and other ncRNAs such as circRNA, lncRNA, and piRNA, in forensic practice, including the identification of tissues and body fluids, cause-of-death analysis, time-related estimation, age estimation, and the identification of monozygotic twins. The close links between ncRNAs and forensic medicine are presented, and their research values and application prospects in forensic medicine are also discussed.

Bilateral Peters' anomaly, aniridia and Wilms tumour (WAGR syndrome) in monozygotic twins.

AIM: This study reports the bilateral association of Peters' anomaly and congenital aniridia in monozygotic twins subsequently diagnosed with Wilms tumour (WAGR syndrome). METHODS: Two monozygotic female twins were referred at age 2 months with bilateral corneal opacity. A diagnosis of Peters' anomaly associated to aniridia was made in both eyes of both twins. Physical examination and ultrasonography were carried out at 12 months of age to explore the possibility of WAGR-related anomalies, specifically Wilms tumour. DNA were isolated and subjected to whole exome sequencing. RESULTS: Peters' anomaly associated to aniridia in both eyes as well as bilateral Wilms tumour in both children were diagnosed. Exome analyses showed a large heterozygous deletion encompassing 6 648 473 bp in chromosome 11p13, using Integrative Genomics Viewer and AnnotSV software. CONCLUSION: WAGR syndrome is a rare contiguous gene deletion syndrome with a greater risk of developing Wilms tumour associated with Peters' anomaly and congenital aniridia. However, co-occurrence of both anomalies was rarely reported in twins, and never in both eyes of monozygotic twins. Here, we report the bilateral association of Peters' anomaly and congenital aniridia in monozygotic twins with WAGR syndrome.

First case of dichorionic diamniotic triplet pregnancy after single blastocyst transfer.

Multiple pregnancies are associated with significant maternal, fetal, and neonatal risks, including prematurity, low birth weight, pre-eclampsia, anemia, postpartum hemorrhage, intrauterine growth restriction, neonatal morbidity, and increased neonatal and infant mortality rates. Assisted reproductive technology (ART) treatments should prioritize efforts to reduce such events, resisting patient demand for the transfer of multiple embryos at each transfer to increase success rates. Extended culture, embryo selection, and single blastocyst transfer can mitigate the risk of high-order multiple pregnancies. Intriguingly, elective single-embryo transfer (eSET) greatly reduces, but does not completely eliminate, the likelihood of multiple gestations. The occurrence of monozygotic twinning (MZT) gives rise to identical twins. It is more prevalent in women undergoing in vitro fertilization (IVF) compared with natural conception. In fact, the reported risks of monozygotic twinning in IVF and natural conception are 1.7 and 0.4%, respectively. The factors suspected to increase the risk of MZT in IVF are multiple embryo transfer, micromanipulation, and extended in vitro culture. Determining chorionicity and amnionicity is crucial in the assessment of multiple pregnancies during the first-trimester ultrasound examination. Dichorionic twins result from embryo splitting within 3 days after fertilization, while monochorionic twins occur when the splitting takes place between 4 and 8 days after fertilization. These timings are suggested by observations carried out in natural pregnancies. In ART, there is evidence of dichorionic twins derived from single embryo transfer (SET). Here, we report a case of dichorionic diamniotic triplets after a single blastocyst transfer occurred in our center. To our knowledge, this is the first case documented so far.

Identifying genetic variants regulating MGMT gene expression - A study in monozygotic Danish twins.

Identifying genetic factors affecting the regulation of the O-6-Methylguanine-DNA Methyltransferase (MGMT) gene and estimating the genetic contribution of the MGMT gene through within-pair correlation in monozygotic twin pairs is of particular importance in various types of cancer such as glioblastoma. We used gene expression data in whole blood from 448 monozygotic twins from the Middle Age Danish Twins (MADT) study to investigate genetic regulation of the MGMT gene by performing a genome-wide association study (GWAS) of the variation in MGMT expression. Additionally, we estimated within-pair dependence measures of the expression values looking for the genetic influence of significant identified genes. We identified 243 single nucleotide polymorphisms (SNPs) significantly (p < 5e-8) associated with expression of MGMT, all located on chromosome 10 near the MGMT gene. Of the 243 SNPs, 7 are novel cis-eQTLs. By further looking into the suggestively significant SNPs (increasing cutoff to p = 1e-6), we identified 11 suggestive trans-eQTLs located on chromosome 17. These variants were in or proximal to a total of seven genes, which may regulate MGMT expression. The within-pair correlation of the expression of MGMT, TRIM37, and SEPT4 provided the upper bound genetic influence of these genes. Overall, identifying cis- or trans-acting genetic variations regulating the MGMT gene can pave the way for a better understanding of the MGMT gene function and ultimately in understanding the patient's sensitivity to therapeutic alkylating agents.

Genome-wide DNA methylation analysis of discordant monozygotic twins reveals consistent sites of differential methylation associated with congenital heart disease.

BACKGROUND: Despite being essentially genetically identical, monozygotic (MZ) twins can be discordant for congenital heart disease (CHD), thus highlighting the importance of in utero environmental factors for CHD pathogenesis. This study aimed to identify the epigenetic variations between discordant MZ twin pairs that are associated with CHD at birth. METHODS: Cord blood of CHD-discordant MZ twins from the Chongqing Longitudinal Twin Study Cohort was subjected to whole-genome bisulfite sequencing, then validated by MeDIP-qPCR and qRT-PCR. RESULTS: 379 DMRs mapped to 175 differentially methylated genes (DMGs) were associated with CHD. Functional enrichment analysis identified these DMGs are involved in histone methylation, actin cytoskeleton organization, the regulation of cell differentiation, and adrenergic signaling in cardiomyocytes. Of note, SPESP1 and NOX5 were hypermethylated in CHD, and associated with lower gene expression levels. CONCLUSIONS: Specific DNA methy (DNAm) variations in cord blood were associated with CHD, thus illustrating new biomarkers and potential interventional targets for CHD. TRIAL REGISTRATION: ChiCTR-OOC-16008203, registered on 1 April 2016 at the Chinese Clinical Trial Registry.

Prenatal diagnosis of monozygotic twins with phenotypic differences in chromosome 17q12 deletion syndrome.

We present a case study highlighting prenatal ultrasound findings in monozygotic twins with chromosome 17q12 deletion syndrome. Fetus A exhibited bilateral fetal pyelectasis and talipes equinovarus, while fetus B showed hyperechogenic kidneys. Despite sharing the same de novo variant, the twins displayed distinct clinical phenotypes, suggesting the presence of non-genetic factors influencing the phenotypic variability of this syndrome. This case represents the first documented instance of prenatally identified identical twins affected by 17q12 deletion syndrome.

Transition of allele-specific DNA hydroxymethylation at regulatory loci is associated with phenotypic variation in monozygotic twins discordant for psychiatric disorders.

BACKGROUND: Major psychiatric disorders such as schizophrenia (SCZ) and bipolar disorder (BPD) are complex genetic mental illnesses. Their non-Mendelian features, such as those observed in monozygotic twins discordant for SCZ or BPD, are likely complicated by environmental modifiers of genetic effects. 5-Hydroxymethylcytosine (5hmC) is an important epigenetic mark in gene regulation, and whether it is linked to genetic variants that contribute to non-Mendelian features remains largely unexplored. METHODS: We combined the 5hmC-selective chemical labeling method (5hmC-seq) and whole-genome sequencing (WGS) analysis of peripheral blood DNA obtained from monozygotic (MZ) twins discordant for SCZ or BPD to identify allelic imbalances in hydroxymethylome maps, and examined association of allele-specific hydroxymethylation (AShM) transition with disease susceptibility based on Bayes factors (BF) derived from the Bayesian generalized additive linear mixed model. We then performed multi-omics integrative analysis to determine the molecular pathogenic basis of those AShM sites. We finally employed luciferase reporter, CRISPR/Cas9 technology, electrophoretic mobility shift assay (EMSA), chromatin immunoprecipitation (ChIP), PCR, FM4-64 imaging analysis, and RNA sequencing to validate the function of interested AShM sites in the human neuroblastoma SK-N-SH cells and human embryonic kidney 293T (HEK293T) cells. RESULTS: We identified thousands of genetic variants associated with AShM imbalances that exhibited phenotypic variation-associated AShM changes at regulatory loci. These AShM marks showed plausible associations with SCZ or BPD based on their effects on interactions among transcription factors (TFs), DNA methylation levels, or other epigenomic marks and thus contributed to dysregulated gene expression, which ultimately increased disease susceptibility. We then validated that competitive binding of POU3F2 on the alternative allele at the AShM site rs4558409 (G/T) in PLLP-enhanced PLLP expression, while the hydroxymethylated alternative allele, which alleviated the POU3F2 binding activity at the rs4558409 site, might be associated with the downregulated PLLP expression observed in BPD or SCZ. Moreover, disruption of rs4558409 promoted neural development and vesicle trafficking. CONCLUSION: Our study provides a powerful strategy for prioritizing regulatory risk variants and contributes to our understanding of the interplay between genetic and epigenetic factors in mediating SCZ or BPD susceptibility.

A case of monozygotic twins with hereditary spastic paraplegia type 4 and epilepsy, of whom only one developed narcolepsy type 1.

We report a case of monozygotic twin sisters with hereditary spastic paraplegia type 4 (SPG4) and epilepsy, only one of whom had a diagnosis of narcolepsy type 1 (NT1). The older sister with NT1 exhibited excessive daytime sleepiness, cataplexy, sleep-onset rapid eye movement period in the multiple sleep latency test, and decreased orexin levels in cerebrospinal fluid. Both sisters had HLA-DRB1*15:01-DQB1*06:02 and were further identified to have a novel missense mutation (c.1156A > C, p.Asn386His) in the coding exon of the spastin (SPAST) gene. The novel missense mutation might be involved in the development of epilepsy. This case is characterised by a combined diagnosis of SPG4 and epilepsy, and it is the first report of NT1 combined with epilepsy and genetically confirmed SPG4. The fact that only one of the twins has NT1 suggests that acquired and environmental factors are important in the pathogenesis of NT1.

Discrimination of monozygotic twins using mtDNA heteroplasmy through probe capture enrichment and massively parallel sequencing.

Differentiating between monozygotic (MZ) twins remains difficult because they have the same genetic makeup. Applying the traditional STR genotyping approach cannot differentiate one from the other. Heteroplasmy refers to the presence of two or more different mtDNA copies within a single cell and this phenomenon is common in humans. The levels of heteroplasmy cannot change dramatically during transmission in the female germ line but increase or decrease during germ-line transmission and in somatic tissues during life. As massively parallel sequencing (MPS) technology has advanced, it has shown the extraordinary quantity of mtDNA heteroplasmy in humans. In this study, a probe hybridization technique was used to obtain mtDNA and then MPS was performed with an average sequencing depth of above 4000. The results showed us that all ten pairs of MZ twins were clearly differentiated with the minor heteroplasmy threshold at 1.0%, 0.5%, and 0.1%, respectively. Finally, we used a probe that targeted mtDNA to boost sequencing depth without interfering with nuclear DNA and this technique can be used in forensic genetics to differentiate the MZ twins.

A longitudinal study on language acquisition in monozygotic twins concordant for autism and hyperlexia.

BACKGROUND: Hyperlexia, a strong orientation towards written materials, along with a discrepancy between the precocious acquisition of decoding skills and weaker comprehension abilities, characterizes up to 20% of autistic children. Sometimes perceived as an obstacle to oral language acquisition, hyperlexia may alternatively be the first step in a non-social pathway of language acquisition in autism. METHOD: We describe two monozygotic twin brothers, both autistic and hyperlexic, from the ages of 4 to 8 years old. Following an in-depth diagnostic assessment, we investigated cross-sectionally and longitudinally their verbal and non-verbal cognitive abilities, language, reading and writing skills, interests, and strengths. RESULTS: The twins' features, including their high non-verbal level of intelligence, their special interests, and their skills in various domains, were highly similar. Their language consisted exclusively of letters and numbers until their fourth year. After that, their vocabulary broadened until they developed full sentences, and their perception-related interests expanded and merged over time to serve the development of other skills. CONCLUSION: Our results show that hyperlexic skills can be harnessed to favor oral language development. Given the strong concordance between the twins' cognitive and behavioral phenotypes, we discuss the environmental and genetic influence that could explain their abilities.

In search of environmental risk factors for obsessive-compulsive disorder: study protocol for the OCDTWIN project.

BACKGROUND: The causes of obsessive-compulsive disorder (OCD) remain unknown. Gene-searching efforts are well underway, but the identification of environmental risk factors is at least as important and should be a priority because some of them may be amenable to prevention or early intervention strategies. Genetically informative studies, particularly those employing the discordant monozygotic (MZ) twin design, are ideally suited to study environmental risk factors. This protocol paper describes the study rationale, aims, and methods of OCDTWIN, an open cohort of MZ twin pairs who are discordant for the diagnosis of OCD. METHODS: OCDTWIN has two broad aims. In Aim 1, we are recruiting MZ twin pairs from across Sweden, conducting thorough clinical assessments, and building a biobank of biological specimens, including blood, saliva, urine, stool, hair, nails, and multimodal brain imaging. A wealth of early life exposures (e.g., perinatal variables, health-related information, psychosocial stressors) are available through linkage with the nationwide registers and the Swedish Twin Registry. Blood spots stored in the Swedish phenylketonuria (PKU) biobank will be available to extract DNA, proteins, and metabolites, providing an invaluable source of biomaterial taken at birth. In Aim 2, we will perform within-pair comparisons of discordant MZ twins, which will allow us to isolate unique environmental risk factors that are in the causal pathway to OCD, while strictly controlling for genetic and early shared environmental influences. To date (May 2023), 43 pairs of twins (21 discordant for OCD) have been recruited. DISCUSSION: OCDTWIN hopes to generate unique insights into environmental risk factors that are in the causal pathway to OCD, some of which have the potential of being actionable targets.

Mitochondrial DNA Copy Number and Heteroplasmy in Monozygotic Twins Discordant for Schizophrenia.

Schizophrenia (SZ) is a severe, complex, and common mental disorder with high heritability (80%), an adult age of onset, and high discordance (∼50%) in monozygotic twins (MZ). Extensive studies on familial and non-familial cases have implicated a number of segregating mutations and de novo changes in SZ that may include changes to the mitochondrial genome. Yet, no single universally causal variant has been identified, highlighting its extensive genetic heterogeneity. This report specifically focuses on the assessment of changes in the mitochondrial genome in a unique set of monozygotic twins discordant (MZD) for SZ using blood. Genomic DNA from six pairs of MZD twins and two sets of parents (N = 16) was hybridized to the Affymetrix Human SNP Array 6.0 to assess mitochondrial DNA copy number (mtDNA-CN). Whole genome sequencing (WGS) and quantitative polymerase chain reaction (qPCR) was performed for a subset of MZD pairs and their parents and was also used to derive mtDNA-CN estimates. The WGS data were further analyzed to generate heteroplasmy (HP) estimates. Our results show that mtDNA-CN estimates for within-pair and mother-child differences were smaller than comparisons involving unrelated individuals, as expected. MZD twins showed discordance in mtDNA-CN estimates and displayed concordance in directionality of differences for mtDNA-CN across all technologies. Further, qPCR performed better than Affymetrix in estimating mtDNA-CN based on relatedness. No reliable differences in HP were detected between MZD twins. The within-MZD differences in mtDNA-CN observed represent postzygotic somatic changes that may contribute to discordance of MZ twins for diseases, including SZ.

Cap Analysis of Gene Expression Clarifies Transcriptomic Divergence Within Monozygotic Twin Pairs.

Phenotypic variation is the result of gene expression based on complex interaction between genetic and environmental factors. It is well known that genetic and environmental factors influence gene expression, but our understanding of their relative importance remains limited. To obtain a hint for the understanding of their contributions, we took advantage of monozygotic twins, as they share genetic and shared environmental factors but differ in nonshared factors, such as environmental differences and stochastic factors. In this study, we performed cap analysis of gene expression on three pairs of twins and clustered each individual based on their expression profiles of annotated genes. The dendrogram of annotated gene transcripts showed a monophyletic clade for each twin pair. We also analyzed the expression of retrotransposons, such as human endogenous retroviruses (HERVs) and long interspersed nuclear elements (LINEs), given their abundance in the genome. Clustering analyses demonstrated that HERV and LINE expression diverged even within monozygotic twin pairs. Thus, HERVs and LINEs are more susceptible to nonshared factors than annotated genes. Motif analysis of differentially expressed annotated genes suggests that specificity protein/Krüppel-like factor family transcription factors are involved in the expression divergence of annotated gene influenced by nonshared factors. Collectively, our findings suggest that expressions of annotated genes and retrotransposons are differently regulated, and that the expression of retrotransposons is more susceptible to nonshared factors than annotated genes.

Early Spontaneous Twinning Recorded By Time-Lapse.

Monozygotic twins (MZT) are 2.5 times more frequent in ART than in natural conceptions. A number of ART-related mechanisms have been probably linked with MZT. Studies that retrospectively analyze the time-lapse (TL) records resulting in MZT suggest that some morphokinetic traits of the inner cell mass and the trophectoderm could be predictors of MZT, but results are controversial. We present the complete TL record of one case of MZT that split itself at the very moment of the division into two cells, with one of the cells coming out through a hole in the zona pellucida (ZP). Both resulting embryos developed normally, and were vitrified. It is suggested that the hole in the ZP may facilitate the extrusion of some cells of the

Comprehensive Multiomics Analysis of Monozygotic Twin Discordant for Double Outlet Right Ventricle.

The objective of this study was to understand and measure epigenetic changes associated with the occurrence of CHDs by utilizing the discordant monozygotic twin model. A unique set of monozygotic twins discordant for double-outlet right ventricles (DORVs) was used for this multiomics study. The cardiac and muscle tissue samples from the twins were subjected to whole genome sequencing, whole genome bisulfite sequencing, RNA-sequencing and liquid chromatography-tandem mass spectrometry analysis. Sporadic DORV cases and control fetuses were used for validation. Global hypomethylation status was observed in heart tissue samples from the affected twins. Among 36,228 differentially methylated regions (DMRs), 1097 DMRs involving 1039 genes were located in promoter regions. A total of 419 genes, and lncRNA-mRNA pairs involved 30 genes, and 62 proteins were significantly differentially expressed. Multiple omics integrative analysis revealed that five genes, including BGN, COL1A1, COL3A1, FBLN5, and FLAN, and three pathways, including ECM-receptor interaction, focal adhesion and TGF-ß signaling pathway, exhibited differences at all three levels. This study demonstrates a multiomics profile of discordant twins and explores the possible mechanism of DORV development. Global hypomethylation might be associated with the risk of CHDs. Specific genes and specific pathways, particularly those involving ECM-receptor interaction, focal adhesion and TGF-ß signaling, might be involved in the occurrence of CHDs.

Immune signatures of prodromal multiple sclerosis in monozygotic twins.

The tremendous heterogeneity of the human population presents a major obstacle in understanding how autoimmune diseases like multiple sclerosis (MS) contribute to variations in human peripheral immune signatures. To minimize heterogeneity, we made use of a unique cohort of 43 monozygotic twin pairs clinically discordant for MS and searched for disease-related peripheral immune signatures in a systems biology approach covering a broad range of adaptive and innate immune populations on the protein level. Despite disease discordance, the immune signatures of MS-affected and unaffected cotwins were remarkably similar. Twinship alone contributed 56% of the immune variation, whereas MS explained 1 to 2% of the immune variance. Notably, distinct traits in CD4+ effector T cell subsets emerged when we focused on a subgroup of twins with signs of subclinical, prodromal MS in the clinically healthy cotwin. Some of these early-disease immune traits were confirmed in a second independent cohort of untreated early relapsing-remitting MS patients. Early involvement of effector T cell subsets thus points to a key role of T cells in MS disease initiation.