What do the new American College of Medical Genetics and Genomics (ACMG) guidelines mean for the provision of non-invasive prenatal genetic screening?

Discovery of Novel Variants on the CHD7 Gene: A Case Series of CHARGE Syndrome

Background: CHARGE syndrome (CS) is a single-gene genetic disorder with multiple organ malformations caused by a variant of the chromodomain helicase DNA-binding protein 7 (CHD7) gene on chromosome 8q12.1. In this study, we aimed to investigate new variants that have emerged in these cases compared with typical CS and the relationship between the genes and phenotypes. Methods: Patients with suspected genetic diseases were subjected to Whole Exome Sequencing (WES) at a genetics laboratory in Guangzhou. The average sequencing coverage depth was >200 ×, and 96% was >20 ×. The variant interpretation was manipulated according to the American College of Medical Genetics (ACMG) guidelines. Molecular data on databases for ClinVar and CHD7 were also collected and collated. We reviewed the currently described CHD7 variants and analyzed the genetic variation and phenotypic heterogeneity. Results: Data of 12 patients with CS from four hospitals in China were collected. According to gestational age, most of them (8/12) were near-term babies with a lower birth weight than their peers, averaging 2.62 kg. In this study, the most common phenotypes were respiratory tract malformations (11/12), heart malformations (10/12), and central nervous system malformations (9/12). Two fetuses were confirmed to have brain or heart abnormalities during prenatal testing, while 10/12 were found to have abnormalities during prenatal testing. The maximum Acute Physiology and Chronic Health Evaluation (APACHE II) score at admission was 19, and the average was 11.58. Five variants in the CHD7 gene c.7012C > T (p.Q2338*), c.7868delC (p.P2623Rfs*16), c.5405-3C > G, c.6936 + 2T > C, and c.8077-2A > G) were novel and were located in exons 33, 36, and introns 25, 32, and 37, respectively. There may be a positive correlation between exon location and phenotype. Conclusion: Five novel variants were discovered. These expanded the mutational spectrum of the CHD7 gene and the phenotype of CS. There may be a correlation between the new mutation sites and the phenotype, which has some reference value for the evaluation of mutation sites.

Noninvasive prenatal testing: the aspects of its introduction into clinical practice

The last couple of years have witnessed the rapid development of prenatal molecular-based screening for fetal aneuploidies that utilizes the analysis of cell-free DNA circulating in the bloodstream of a pregnant woman. The present review looks at the potential and limitations of such testing and the possible causes of false-positive and false-negative results. The review also describes the underlying principles of data acquisition and analysis the testing involves. In addition, we talk about the opinions held by the expert community and some aspects of legislation on the use of noninvasive prenatal testing (NIPT) in clinical practice in the countries where NIPT is much more widespread than in Russia.