Copy Number Variants and Exome Sequencing Analysis in Six Pairs of Chinese Monozygotic Twins Discordant for Congenital Heart Disease

Cardiac arrhythmia in individuals with steroid sulfatase deficiency (X-linked ichthyosis): candidate anatomical and biochemical pathways

Circulating steroids, including sex hormones, can affect cardiac development and function. In mammals, steroid sulfatase (STS) is the enzyme solely responsible for cleaving sulfate groups from various steroid molecules, thereby altering their activity and water solubility. Recent studies have indicated that Xp22.31 genetic deletions encompassing STS (associated with the rare dermatological condition X-linked ichthyosis), and common variants within the STS gene, are associated with a markedly elevated risk of cardiac arrhythmias, notably atrial fibrillation/flutter. Here, we consider emerging basic science and clinical findings which implicate structural heart abnormalities (notably septal defects) as a mediator of this heightened risk, and propose candidate cellular and biochemical mechanisms. Finally, we consider how the biological link between STS activity and heart structure/function might be investigated further and the clinical implications of work in this area.

Feature selection with a genetic algorithm can help improve the distinguishing power of microbiota information in monozygotic twins' identification

INTRODUCTION

Personal identification of monozygotic twins (MZT) has been challenging in forensic genetics. Previous research has demonstrated that microbial markers have potential value due to their specificity and long-term stability. However, those studies would use the complete information of detected microbial communities, and low-value species would limit the performance of previous models.

METHODS

To address this issue, we collected 80 saliva samples from 10 pairs of MZTs at four different time points and used 16s rRNA V3-V4 region sequencing to obtain microbiota information. The data formed 280 inner-individual (Self) or MZT sample pairs, divided into four groups based on the individual relationship and time interval, and then randomly divided into training and testing sets with an 8:2 ratio. We built 12 identification models based on the time interval ( ≤ 1 year or ≥ 2 months), data basis (Amplicon sequence variants, ASVs or Operational taxonomic unit, OTUs), and distance parameter selection (Jaccard distance, Bray-Curist distance, or Hellinger distance) and then improved their identification power through genetic algorithm processes. The best combination of databases with distance parameters was selected as the final model for the two types of time intervals. Bayes theory was introduced to provide a numerical indicator of the evidence's effectiveness in practical cases.

RESULTS

From the 80 saliva samples, 369 OTUs and 1130 ASVs were detected. After the feature selection process, ASV-Jaccard distance models were selected as the final models for the two types of time intervals. For short interval samples, the final model can completely distinguish MZT pairs from Self ones in both training and test sets.

DISCUSSION

Our findings support the microbiota solution to the challenging MZT identification problem and highlight the importance of feature selection in improving model performance.

Ankyloglossia in Monochorionic Diamniotic and Dichorionic Diamniotic Twins: A Cross-Sectional Study

Objective: To determine the prevalence of ankyloglossia in diamniotic monochorionic and diamniotic dichorionic twins, as well as to verify the relationship between gender and type of pregnancy. Study Design: A cross-sectional observational study, carried out with 52 pairs of dichorionic/diamniotic twins and 49 monochorionic/diamniotic pairs. The data collection was carried out through the analysis of medical records and the results of the Neonatal Screening of the Tongue Frenulum Assessment Protocol in Babies, and corresponded to the period of 2 years (2020-2022). Statistical analysis of data was performed, considering the significance value of 5%. The study was approved by the Human Research Ethics Committee of the institution. Results: The statistical analysis of multiple logistic regression between the two groups of twins (Mono/Di and Di/Di) according to the socioeconomic, demographic, and clinical-epidemiological profile was statistically significant for some variables. The prevalence of ankyloglossia, according to the type of twin pregnancy, showed a statistically significant difference. There was no statistical difference in relation to sex and ankyloglossia, or between couples diagnosed with ankyloglossia according to the type of pregnancy. Conclusion: Monochorionic/diamniotic twins had a higher prevalence of ankyloglossia, regardless of gender.

Two genetic variants in NEXN and ABCC6 genes found in a patient with right coronary artery to right ventricle fistula combined with giant coronary aneurysm and patent ductus arteriosus

Objective

Coronary artery fistula, defined as communication between a coronary artery and a great vessel or a cardiac chamber, is a relatively rare anomaly with an estimated incidence of 0.002% in the general population. It could be combined with a giant coronary artery aneurysm, with an incidence of 5.9% of the total incidence rate of CAF in the general population. The pathogenesis of these two combined anomalies is not clear, and we aimed to detect whether genetic abnormalities underlie the pathogenesis of these rarely combined anomalies.

Materials and methods

A 6-year-old patient with a diagnosis of the right coronary artery to right ventricle fistula combined with a giant right coronary artery aneurysm and patent ductus arteriosus underwent a surgical repair at our center. The diagnosis was confirmed by echocardiography, CT, and surgery. DNA was extracted from the peripheral venous blood samples of the patient and his mother after informed consent was obtained. Hematoxylin and Eosin (HE) and Alizarin red staining were performed on the excised coronary artery aneurysm. Exome sequencing and in silico analyses were performed to detect detrimental genetic variants.

Results

No obvious abnormalities were found in the excised coronary artery aneurysm. A heterozygous truncated variant (NM_144573: c.G298T; p.G100X) in the NEXN gene and a missense variant (NM_001171: c.G1312A; p.V438M) in the ABCC6 gene were carried by the patient but not by his mother.

Conclusion

The NEXN-truncated variant, NEXN-G100X, is associated with the development of coronary arteries and congenital coronary artery anomalies.

Diagnosis and treatment of congenital tricuspid valve malformation in a case of monozygotic twins

Background

Congenital tricuspid valve malformations are known to occur, but tricuspid valve malformations associated with twins are rarely reported. We report this case from the point of view of a medical history, an auxiliary examination and a genetic pathogenesis to provide a reference for our peers.

Case presentation

We report a rare case of congenital heart disease in monozygotic twins of Hui nationality in Yunnan-Guizhou Plateau, they are normal conception. Twin 1 had Ebstein’s anomaly, and received surgical treatment and recovered satisfactorily. Twin 2 had only partial tricuspid septal prolapse, and pulmonary hypertension occurred during follow-up.

Conclusions

It is necessary to carry out individualized diagnosis and treatment for twins and follow-up observation by echocardiography for a long time. Choosing the right time for cardiac surgery is of great significance to the treatment of the disease.

Prenatal diagnosis and management of monozygotic twins discordant for severe fetal abnormalities

OBJECTIVE

We present prenatal diagnosis and management of monozygotic (MZ) twins discordant for severe fetal abnormalities.

CASE REPORT

A 36-year-old woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age, and hydrops fetalis, a giant cystic hygroma of 5 × 3.5 cm and left hydronephrosis in a co-twin. The other co-twin was structurally normal. Amniocentesis revealed a karyotype of 46,XY in both co-twins. Simultaneous polymorphic DNA marker analysis using the DNAs extracted from maternal blood and uncultured amniocytes confirmed MZ twinning. The woman underwent a successful selective fetal reduction by radiofrequency ablation at 22 weeks of gestation. At 28 weeks of gestation, premature rupture of membranes occurred, and a 1280-g normal male baby and a 275-g dead malformed co-twin were delivered. The normal co-twin was phenotypically normal and was doing well at age seven weeks.

CONCLUSIONS

Prenatal diagnosis of MZ twins discordant for structural abnormalities should include a differential diagnosis of MZ twinning, and a zygosity test is necessary under such a circumstance.

Discordant congenital heart defects in monochorionic twins: Risk factors and proposed pathophysiology

A six-fold increase in congenital heart defects (CHD) exists among monochorionic (MC) twins compared to singleton or dichorionic twin pregnancies. Though MC twins share an identical genotype, discordant phenotypes related to CHD and other malformations have been described, with reported rates of concordance for various congenital anomalies at less than 20%. Our objective was to characterize the frequency and spectrum of CHD in a contemporary cohort of MC twins, coupled with genetic and clinical variables to provide insight into risk factors and pathophysiology of discordant CHD in MC twins. Retrospective analysis of all twins receiving prenatal fetal echocardiography at a single institution from January 2010 –March 2020 (N = 163) yielded 23 MC twin pairs (46 neonates) with CHD (n = 5 concordant CHD, n = 18 discordant CHD). The most common lesions were septal defects (60% and 45.5% in concordant and discordant cohorts, respectively) and right heart lesions (40% and 18.2% in concordant and discordant cohorts, respectively). Diagnostic genetic testing was abnormal for 20% of the concordant and 5.6% of the discordant pairs, with no difference in rate of abnormal genetic results between the groups (p = 0.395). No significant association was found between clinical risk factors and development of discordant CHD (p>0.05). This data demonstrates the possibility of environmental and epigenetic influences versus genotypic factors in the development of discordant CHD in monochorionic twins.

Brain features of nearly drug-naïve female monozygotic twins with first-episode schizophrenia and the classification accuracy of brain feature patterns: A pilot study

BACKGROUND

Data on differences in brain features between monozygotic (MZ) twins with and without schizophrenia are scarce.

METHODS

We compared brain features of female MZ twins with and without first-episode schizophrenia and healthy controls (n = 20 each). Voxel-based morphometry and tract-based spatial statistics were used to analyze differences in brain structure. Whole-brain effective connectivity (EC) and functional connectivity (FC) networks were constructed using resting-state functional magnetic resonance imaging (rs-fMRI) data.

RESULTS

Female twins with schizophrenia exhibited abnormal gray matter volume (GMV) in the basal ganglia and prefrontal and parietal cortices, impairments in the arcuate fasciculus, and significant disruptions (primarily decreases) in nine EC networks. They exhibited rs-EC alterations involving the limbic areas and subcortex. Combined rs-EC and rs-FC data distinguished twins with first-episode schizophrenia with high accuracy. Combined consideration of structural and functional features enabled the distinction of female MZ twins with schizophrenia from those without schizophrenia and healthy controls with 100% accuracy.

CONCLUSIONS

Female MZ twins with schizophrenia exhibited increased GMV, white matter impairment, and disruptions in EC and FC networks. The combination of rs-EC + rs-FC data could distinguish female twins with schizophrenia from twins without schizophrenia and healthy controls with 97.4% accuracy, and the addition of structural brain features yielded a 100% accuracy rate. These findings may provide pivotal insight for further study of the mechanisms underlying schizophrenia.

The Needle in the Haystack-Searching for Genetic and Epigenetic Differences in Monozygotic Twins Discordant for Tetralogy of Fallot

Congenital heart defects (CHDs) are the most common birth defect in human with an incidence of almost 1% of all live births. Most cases have a multifactorial origin with both genetics and the environment playing a role in its development and progression. Adding an epigenetic component to this aspect is exemplified by monozygotic twins which share the same genetic background but have a different disease status. As a result, the interplay between the genetic, epigenetic and the environmental conditions might contribute to the etiology and phenotype. To date, the underlying causes of the majority of CHDs remain poorly understood. In this study, we performed genome-wide high-throughput sequencing to examine the genetic, structural genomic and epigenetic differences of two identical twin pairs discordant for Tetralogy of Fallot (TOF), representing the most common cyanotic form of CHDs. Our results show the almost identical genetic and structural genomic identity of the twins. In contrast, several epigenetic alterations could be observed given by DNA methylation changes in regulatory regions of known cardiac-relevant genes. Overall, this study provides first insights into the impact of genetic and especially epigenetic factors underlying monozygotic twins discordant for CHD like TOF.

Differences of microRNA expression profiles between monozygotic twins' blood samples

Monozygotic (MZ) twins are widely regarded as genetically identical, and traditional DNA typing methods are insufficient in identifying MZ twins. So the discrimination of MZ twins become a forensic problem. MicroRNAs (miRNAs) are a class of small, endogenous, non-protein-coding RNA molecules of approximately 22 nucleotides in length, and exist extensively in a variety of eukaryotic cells. MiRNAs regulate gene expression and play fundamental roles in multiple biological processes, including cell differentiation, proliferation and apoptosis as well as aging and disease processes. The goal of this study is to explore the differential expression of miRNAs within MZ twin pairs, and aimed to find new biomarkers for distinguishing MZ twins. Thus, the miRNA expression profiles of seven pairs of healthy MZ twins of different sex and age were analyzed by miRNA microarray. A total of 545 miRNAs were found to be differentially expressed in these MZ twin pairs, and 2, 5, 22, 53 and 132 differentially expressed miRNAs were shared across six, five, four, three and two pairs of MZ twins respectively. These findings had been confirmed by real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assays on select miRNAs, including miR-151a-3p, miR-3653-3p, miR-142-3p, miR-4325, miR-16-5p, let-7i-5p, miR-222-3p, miR-550b-3p, miR-4791 and miR-27a-3p. The results demonstrated that there are differences in the expression of miRNAs within MZ twin pairs, suggesting a role of miRNAs in identifying MZ twins.