Clinical applications of next-generation sequencing in the diagnosis of genetic disorders in Korea: a narrative review

Next-generation sequencing (NGS) technologies have revolutionized genetic testing and enabled efficient screening of various genetic conditions in clinical settings. However, the clinical application of genetic test results presents numerous significant challenges. This review aims to provide a comprehensive overview of key concepts for the clinical application of NGS, including (1) technical aspects and limitations, (2) variant classification, (3) clinical interpretation, (4) familial testing and genetic counseling, and (5) ethical considerations.Current Concepts: In short-read-based NGS, several limitations exist in detecting genomic variations, including repetitive sequences or complex structural variations. The variant classification process can be influenced by suspected genomic conditions and the accessibility of genomic databases. Therefore, the final genetic diagnosis depends on the physician’s discretion, which relies on the genotype-phenotype correlations and reverse phenotyping through additional evaluations. Familial testing can help trace the origin of variants and allele segregation and aid in variant interpretation, risk assessment, disease prevention, and family planning. In addition to addressing the clinical impact of genetic results, genetic counselors should also consider potential consequences related to ethical, legal, and social issues, including family dynamics.Discussion and Conclusion: NGS-based genetic testing is a promising diagnostic tool for genetic disorders, but proper variant interpretation and clinical evaluation are crucial for optimal clinical practice. Notably, ethical considerations and regulatory measures are required to prepare for the next era of genomic medicine.

Functional Characterization of Pharmcogenetic Variants of Human Cytochrome P450 2C9 in Korean Populations

Human cytochrome P450 2C9 is a highly polymorphic enzyme that is required for drug and xenobiotic metabolism. Here, we studied eleven P450 2C9 genetic variants—including three novel variants F69S, L310V, and Q324X—that were clinically identified in Korean patients. P450 2C9 variant enzymes were expressed in Escherichia coli and their bicistronic membrane fractions were prepared The CO-binding spectra were obtained for nine enzyme variants, indicating P450 holoenzymes, but not for the M02 (L90P) variant. The M11 (Q324X) variant could not be expressed due to an early nonsense mutation. LC-MS/MS analysis was performed to measure the catalytic activities of the P450 2C9 variants, using diclofenac as a substrate. Steady-state kinetic analysis revealed that the catalytic efficiency of all nine P450 2C9 variants was lower than that of the wild type P450 2C9 enzyme. The M05 (R150L) and M06 (P279T) variants showed high k(cat) values; however, their K(m) values were also high. As the M01 (F69S), M03 (R124Q), M04 (R125H), M08 (I359L), M09 (I359T), and M10 (A477T) variants exhibited higher K(m) and lower k(cat) values than that of the wild type enzyme, their catalytic efficiency decreased by approximately 50-fold compared to the wild type enzyme. Furthermore, the novel variant M07 (L310V) showed lower k(cat) and K(m) values than the wild type enzyme, which resulted in its decreased (80%) catalytic efficiency. The X-ray crystal structure of P450 2C9 revealed the presence of mutations in the residues surrounding the substrate-binding cavity. Functional characterization of these genetic variants can help understand the pharmacogenetic outcomes.

An 18.3-Mb Duplication on Chromosome 14q With Multiple Cardiac Anomalies and Clubfoot Was Identified by Microarray Analysis

No abstract available.

Bacteroides nordii and Bacteroides salyersiae Isolated from Post-operative Peritonitis Patients

In this study, we report three cases in which two species of the Bacteroides fragilis group, 'Bacteroides nordii' and 'Bacteroides salyersiae', were isolated from peritoneal fluid cultures from post-operative peritonitis patients. The two species of the B. fragilis group were initially misidentified as B. fragilis/Bacteroides stercoris and Bacteroides ovatus by Rapid ID 32A (bioMérieux, France), and finally confirmed as B. nordii and B. salyersiae using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and 16s rRNA sequencing. For the identification of anaerobes, particularly B. fragilis group organisms, MALDI-TOF MS is a useful method not only because of its concordance with 16S rRNA sequencing results, but also because of its rapidity and simple procedure.