Copy number variants and the genetic enigma of congenital heart disease

Influence of different concentrations of ozone on the alteration of mitochondrial DNA copy numbers in human peripheral blood

By now, O₃ pollution has become a main environmental problem. O₃ is a prevalent risk factor for many diseases, but the regulatory factors linking O₃ and diseases remain ambiguous. Mitochondrial DNA (mtDNA) is the genetic material in mitochondria, which plays a key role in the production of respiratory ATP. Due to a lack of histone protection, mtDNA is easily damaged by ROS, and O₃ is an important source to stimulate the production of endogenous ROS in vivo. Therefore, we logically speculate that O₃ exposure can alter mtDNA copy number by the induction of ROS. In the present study, we performed a panel study of 65 MSc students at the Chinese research academy of environmental sciences (CRAES) with 3 rounds of follow-up visits from August 2021 to January 2022. We examined the mtDNA copy numbers in the peripheral blood of subjects using quantitative polymerase chain reaction. Linear mixed-effect (LME) model and stratified analysis were used to investigate the association between O₃ exposure and mtDNA copy numbers. We found a dynamic process of the association between the concentration of O₃ exposure and the mtDNA copy number in the peripheral blood. The lower concentration of O₃ exposure did not affect the mtDNA copy number. As the concentration of O₃ exposure increased, the mtDNA copy number also increased. While, when O₃ exposure reached a certain concentration, a decrease in mtDNA copy number was found. This correlation between the concentration of O₃ and the mtDNA copy number could be ascribed to the severity of cellular damage induced by O₃ exposure. Our results provide a new perspective for the discovery of a biomarker of O₃ exposure and health response, as well as for the prevention and treatment of adverse health effects caused by different concentrations of O₃.

Advances in understanding mechanisms underlying mitochondrial structure and function damage by ozone

Mitochondria are double-membraned organelles found in eukaryotic cells. The integrity of mitochondrial structure and function determines cell destiny. Mitochondria are also the "energy factories of cells." The production of energy is accompanied by reactive oxygen species (ROS) generation. Generally, the production and consumption of ROS maintains a balance in cells. Ozone is a highly oxidizing, harmful substance in ground-level atmosphere. Ozone inhalation causes oxidative injury owing to the generation of ROS, resulting in mitochondrial oxidative stress overload. Oxidative damage to the mitochondria induces a vicious cycle of ROS production which might destroy mitochondrial DNA and mitochondrial structure and function in cells. ROS can alter the phosphorylation of various signaling molecules, triggering a series of downstream signaling pathway reactions. These include inflammatory responses, pyroptosis, autophagy, and apoptosis. Changes involving these molecular mechanisms may be related to the occurrence of disease. According to numerous epidemiological investigations, ozone exposure induces respiratory, cardiovascular, and nervous system diseases in humans. In addition, these systems require large quantities of energy. Hence, the mitochondrial damage caused by ozone may act as a bridge between human diseases. However, the specific molecular mechanisms involved require further investigation. This review discusses our understanding of the structure and function of mitochondria the mechanisms underlying ozone-induced mitochondrial damage.

Contribution of Congenital Heart Disorders Associated With Copy Number Variants in Mediating Risk for Brain Developmental Disorders: Evidence From 20-Year Retrospective Cohort Study

Rare pathogenic copy number variants (CNVs) are genetic rearrangements that have been associated with an increased risk for congenital heart disorders (CHDs). However, the association of CNVs with atypical brain development, leading to neurodevelopmental disorders (NDDs), in the presence of CHDs remains unclear. We attempted to explore this association by establishing the prevalence and burden of CNVs associated with CHD in a Welsh population and by studying the effect of rare CNVs associated with CHDs in mediating the risk of NDDs. Toward this goal, we analyzed data from the Congenital Anomaly Register for Wales (CARIS), referred from hospitals in Wales between 1998 and 2018, which included 1,113 subjects in total. Of these, 785 subjects were included in the study following application of the exclusion criteria, and a total of 28 rare CNVs associated with CHD were analyzed. The findings from this cohort study identified 22q11.2 deletion as the most prominent CNV across the cohort. Our data demonstrates that the survival rate of the cohort after 3 years was 99.9%, and mortality fell significantly between 1 and 2 years and between 2 and 3 years [F_(1,27) = 10, p = 0.0027; F_(1,27) = 5.8, p = 0.0222]. Importantly, the data set revealed a positive correlation between the incidence of congenital heart disease and the incidence of neurodevelopmental abnormalities in patients with CNVs across the whole cohort [95% CI (0.4062, 0.8449), p < 0.0001, r = 0.6829]. Additionally, we identified significant CNVs that result in the co-morbidity of CHD and NDD and show that septal defects and global developmental delay are major congenital defects. Further research should identify a common molecular mechanism leading to the phenotypic comorbidity of CHDs and NDDs, arising from a common CNV, which can have an implication for improving risk classification and for fetal neuroprotection strategies in the affected children and in precision medicine.

Chromosomal microarray analysis for the detection of chromosome abnormalities in fetuses with echogenic intracardiac focus in women without high-risk factors

To investigate the association between pathogenic copy number variants (p-CNVs) and abnormal karyotypes detected by chromosomal microarray analysis (CMA) and echogenic intracardiac focus (EIF).This was a retrospective study of fetuses with EIF with CMA data at the Prenatal Diagnosis Center of the West China Second University Hospital of Sichuan University between September 2014 and May 2017. Fetuses were assigned to the isolated EIF and non-isolated EIF groups according to the presence of other ultrasound abnormalities.Among 244 pregnant women, there were 143 cases of isolated EIF and 101 of non-isolated EIF. CMA revealed chromosome abnormality (n = 9 (3.7%): trisomy 21, n = 4; sexual trisomy, n = 2; and p-CNV, n = 3), variants of unknown significance (VOUS, n = 19), and benign CNV (b-CNV, n = 216). Among the fetuses with isolated EIF, 5 had chromosomal abnormalities (3.5%). Among the fetuses with non-isolated EIF, four had chromosomal abnormalities (4.0%). All fetuses with trisomy 21 were in the non-isolated group. The frequency of labor induction was 66.7% (6/9) among the fetuses with chromosome abnormality and 21.1% (4/19) among those with VOUS. Among those with chromosomal abnormalities, one (11.1%) had congenital heart disease.In pregnant women without high-risk factors for chromosomal abnormalities, ultrasound abnormalities, including EIF, could be an indication for CMA. Ultrasound abnormalities (including EIF) and chromosome abnormality could indicate a high risk of CHD. The presence of EIF and at least another ultrasound abnormality could indicate a high risk of trisomy 21.

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

Congenital heart disease (CHD) is one of the most common birth defects. More than 200 susceptibility loci have been identified for CHDs, yet a large part of the genetic risk factors remain unexplained. Monozygotic (MZ) twins are thought to be completely genetically identical; however, discordant phenotypes have been found in MZ twins. Recent studies have demonstrated genetic differences between MZ twins. We aimed to test whether copy number variants (CNVs) and/or genetic mutation differences play a role in the etiology of CHDs by using single nucleotide polymorphism (SNP) genotyping arrays and whole exome sequencing of twin pairs discordant for CHDs. Our goal was to identify mutations present only in the affected twins, which could identify novel candidates for CHD susceptibility loci. We present a comprehensive analysis for the CNVs and genetic mutation results of the selected individuals but detected no consistent differences within the twin pairs. Our study confirms that chromosomal structure or genetic mutation differences do not seem to play a role in the MZ twins discordant for CHD.

A Biobank for Long-term and Sustainable Research in the Field of Congenital Heart Disease in Germany

Congenital heart disease (CHD) is the most frequent birth defect (0.8%-1% of all live births). Due to the advance in prenatal and postnatal early diagnosis and treatment, more than 90% of these patients survive into adulthood today. However, several mid- and long-term morbidities are dominating the follow-up of these patients. Due to the rarity and heterogeneity of the phenotypes of CHD, multicenter registry-based studies are required. The CHD-Biobank was established in 2009 with the aim to collect DNA from patients and their parents (trios) or from affected families, as well as cardiovascular tissues from patients undergoing corrective heart surgery for cardiovascular malformations. Clinical/phenotype data are matched to the International Paediatric and Congenital Cardiac Code (IPCCC) and the International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10). The DNA collection currently comprises samples from approximately 4200 participants with a wide range of CHD phenotypes. The collection covers about 430 trios and 120 families with more than one affected member. The cardiac tissue collection comprises 1143 tissue samples from 556 patients after open heart surgery. The CHD-Biobank provides a comprehensive basis for research in the field of CHD with high standards of data privacy, IT management, and sample logistics.