Screening of 22q11.2DS Using Multiplex Ligation-Dependent Probe Amplification as an Alternative Diagnostic Method

The evaluation of the SMAD1 rs1016792 polymorphism and gene expression on pulmonary hypertension due to congenital heart disease in children: a preliminary study

Smad Family Member (SMAD), a protein family responsible for transducing the signal induced by TGF-β into the nucleus, is thought to play a role in the pathology of many heart diseases. Therefore, we aimed to evaluate the influence of the SMAD1 rs1016792 polymorphism and gene expression on pulmonary arterial hypertension (PAH) due to congenital heart disease (CHD) in children. A total of 90 children, 45 of whom were PAH-CHD children and 45 healthy children, were included in the study. Patients were selected from those who were diagnosed and followed in the Department of Pediatric Cardiology.The SMAD1 rs1016792 genotyping and expression analysis was performed using a real-time polymerase chain reaction (RT-PCR)-based system. It was determined that the left ventricular end-diastolic diameter (LVEDD) value was lower in the patient group than in the control group, while the pulmonary artery pressure (PAP) value was higher in the patient group than in the control group. When the SMAD1 gene expression level was examined, a statistically significant difference was found between the patient and control groups. Patients had decreased SMAD1 expression compared to controls (p˂0.001). We found no significant difference between the patient and control groups in terms of SMAD1 rs1016792 genotype distribution or allele frequency (p > 0.05). There was no difference between genotype distribution and SMAD1 expression levels in the groups. In this study, we showed for the first time that SMAD1 expression is decreased in children with PAH-CHD. These results will be a preliminary step toward understanding the role of SMAD1 in the etiopathogenesis of CHD.

Diagnosis of 22q11.2 deletion syndrome in children with congenital heart diseases and facial dysmorphisms

Background

Congenital heart diseases (CHDs) are the leading cause of birth defects. Approximately, 30% of CHDs are related to genetic syndromes accompanied by extracardiac anomalies. Aneuploidies and 22q11.2 deletions account for majority of cases. 22q11.2 deletion involves deletion of 30-40 genes, and varying deletions in this region lead to different phenotypes. Fluorescent in situ hybridization probes span a narrow region on chromosome 22 as compared to other recent techniques like multiplex ligation probe amplification assay (MLPA) which may also identify any gene duplications if present.

Methods

Present study was a cross-sectional descriptive study. In total, 350 children with CHD reported to pediatric cardiology clinic during the study period. Of these, 60 children had associated facial dysmorphism. Out of these 60 children, 18 children had clinical phenotype characteristic of Down syndrome and hence these children were excluded from the study. Forty-two children with CHDs (conotruncal and other defects) and craniofacial features (subtle or obvious) suggestive of 22q11.2 deletion spectrum disorder were included in this study.

Results

Nineteen percent of children presenting with CHDs and facial dysmorphisms had 22q11.2 deletion syndrome. All the samples were subjected to karyotyping.

Conclusion

Metaphase FISH has been the method of choice for microdeletions. However, apart from technical challenges and longer turnaround time, FISH probes span a very narrow region in 22q11.2 chromosome (LCR22 D) and provide information about DiGeorge syndrome (DGS) only. Take home message is that patients of CHDs with facial dysmorphism should be investigated in an approach-based manner.

Chromosomal abnormalities in fetuses with congenital heart disease: a meta-analysis

PURPOSE

The aim of this meta-analysis was to evaluate the risk of chromosomal abnormalities in fetuses with congenital heart disease (CHD).

METHODS

Four literature databases were searched until 17th January 2022 using the relevant medical subject heading terms, word variants, and keywords for "congenital heart defect, fetal, and chromosomal abnormalities". The prevalence of overall chromosomal abnormality, aneuploidy, 22q11 deletion, other copy number variants (CNVs), and variants of unknown significance (VOUS) was analyzed.

RESULTS

45 studies met the inclusion criteria for the analysis. The pooled proportion of overall chromosomal abnormalities, aneuploidy, 22q11 deletion, and other CNVs in fetuses with CHD was 23% (95% CI: 20-26%), 19% (95% CI, 16-22%), 2% (95% CI, 2-3%), and 4% (95% CI, 3-5%), respectively. The incidence of overall chromosomal abnormalities, aneuploidy, and other CNVs in non-isolated CHD was higher than in isolated CHD, with odds ratios of 3.08, 3.45, and 4.02, respectively. The incidence of overall chromosomal abnormalities in septal defects was higher than in conotruncal defects and other defects, with odds ratios of 1.60 and 3.61, respectively. In addition, the pooled proportion of VOUS in CHD was 4%.

CONCLUSION

CHD is commonly associated with chromosomal abnormalities. If karyotyping or fluorescence in situ hybridization is normal, chromosomal microarray should be performed to look for submicroscopic abnormalities, especially in fetuses with non-isolated CHD and septal defects.

Chromosome 22q11.2 Deletion Syndrome: A Comprehensive Review of Molecular Genetics in the Context of Multidisciplinary Clinical Approach

The 22q11.2 deletion syndrome is a multisystemic disorder characterized by a marked variability of phenotypic features, making the diagnosis challenging for clinicians. The wide spectrum of clinical manifestations includes congenital heart defects-most frequently conotruncal cardiac anomalies-thymic hypoplasia and predominating cellular immune deficiency, laryngeal developmental defects, midline anomalies with cleft palate and velar insufficiency, structural airway defects, facial dysmorphism, parathyroid and thyroid gland hormonal dysfunctions, speech delay, developmental delay, and neurocognitive and psychiatric disorders. Significant progress has been made in understanding the complex molecular genetic etiology of 22q11.2 deletion syndrome underpinning the heterogeneity of clinical manifestations. The deletion is caused by chromosomal rearrangements in meiosis and is mediated by non-allelic homologous recombination events between low copy repeats or segmental duplications in the 22q11.2 region. A range of genetic modifiers and environmental factors, as well as the impact of hemizygosity on the remaining allele, contribute to the intricate genotype-phenotype relationships. This comprehensive review has been aimed at highlighting the molecular genetic background of 22q11.2 deletion syndrome in correlation with a clinical multidisciplinary approach.

Screening Method for 22q11 Deletion Syndrome Involving the Use of TaqMan qPCR for TBX1 in Patients with Conotruncal Congenital Heart Disease

22q11.2 deletion syndrome is a phenotypic spectrum that encompasses DiGeorge syndrome (OMIM: 188400) and velocardiofacial syndrome (OMIM: 192430). It is caused by a 1.5–3.0 Mb hemizygous deletion of locus 22q11.2, which leads to characteristic facies, conotruncal cardiovascular malformations, velopharyngeal insufficiency, T-lymphocyte dysfunction due to thymic aplasia, and parathyroid hypoplasia, and, less frequently, neurological manifestations such as delayed psychomotor development or schizophrenia. This study aimed to describe a screening method for the diagnosis of 22q11.2 deletion syndrome in patients with Conotruncal Congenital Heart Disease (CCHD), using qPCR to detect the copy number of the TBX1 gene in a single DNA sample. A total of 23 patients were included; 21 with a biallelic prediction of the TBX1 copy number gene and 2 with a monoallelic prediction who were suspected to be positive and subjected to MLPA confirmation. One patient (4.34%) with truncus arteriosus CCHD was confirmed to have 22q11.2 deletion syndrome. We propose this approach as a possible newborn screening method for 22q11.2 deletion syndrome in CCHD patients.

SMAD1 Loss-of-Function Variant Responsible for Congenital Heart Disease

As the most common form of developmental malformation affecting the heart and endothoracic great vessels, congenital heart disease (CHD) confers substantial morbidity and mortality as well as socioeconomic burden on humans globally. Aggregating convincing evidence highlights the genetic origin of CHD, and damaging variations in over 100 genes have been implicated with CHD. Nevertheless, the genetic basis underpinning CHD remains largely elusive. In this study, via whole-exosome sequencing analysis of a four-generation family inflicted with autosomal-dominant CHD, a heterozygous SMAD1 variation, NM_005900.3: c.264C > A; p.(Tyr88∗), was detected and validated by Sanger sequencing analysis to be in cosegregation with CHD in the whole family. The truncating variation was not observed in 362 unrelated healthy volunteers employed as control persons. Dual-luciferase reporter gene assay in cultured COS7 cells demonstrated that Tyr88∗-mutant SMAD1 failed to transactivate the genes TBX20 and NKX2.5, two already well-established CHD-causative genes. Additionally, the variation nullified the synergistic transcriptional activation between SMAD1 and MYOCD, another recognized CHD-causative gene. These data indicate SMAD1 as a new gene responsible for CHD, which provides new insight into the genetic mechanism underlying CHD, suggesting certain significance for genetic risk assessment and precise antenatal prevention of the family members inflicted with CHD.

DiGeorge syndrome: consider the diagnosis

DiGeorge syndrome (DGS) is caused by a chromosomal microdeletion at 22q11.2 that results in impaired development of the pharyngeal pouch system. Patients with DGS may have developmental abnormalities of craniofacial structures, parathyroid glands, thymus and cardiac outflow tract. Doctors have been routinely testing for DGS in newborns with conotruncal cardiac anomalies since the late 1990s; before then, however, they relied on complex diagnostic criteria and the disease was often missed. Adults born with conotruncal defects before the late 1990s may have undiagnosed DGS. We present one such case: a 35-year-old woman with a cardiac diagnosis of tetralogy of Fallot and unilateral absence of a pulmonary arter who was found to have DGS. Identifying DGS in adults is important both for disease management and genetic counselling. Our case emphasises the importance of screening for DGS in adults who were born with conotruncal cardiac abnormalities before widespread neonatal testing became common.