Cystic fibrosis (CF) is a prevalent monogenic disease caused by mutations in the CFTR gene. Although pathogenetic therapy is highly effective, it is not suitable for all patients, requires lifelong treatment, and is associated with side effects. Consequently, extensive research is being conducted globally to develop etiotropic therapy for CF, particularly focusing on genome editing methods. This review explores the limitations of current therapy, outlines genome editing techniques, and evaluates all currently available data on gene therapy for CF utilizing genome editing techniques

Glutaric aciduria type 2 (GA2), or multiple acyl-CoA dehydrogenase deficiency (MADD, OMIM 231680), is a rare life-threatening disorder associated with impaired metabolism of fatty acids and amino acids. GA2 has been included in the expanded neonatal screening program in the Russian Federation since January, 2023. Following the primary screening in the regional centers, a group of newborns underwent the second stage of confirmatory diagnostics at the Research Center for Medical Genetics (N = 27). Concentrations of amino acids and acylcarnitines in the blood were remeasured using MS/MS, organic acids in the urine were analyzed using GC-MS, and a molecular genetic study of the coding regions of the ETFA, ETFB, and ETFDH genes was conducted. GA2 was confirmed in 6 patients. The frequency of GA2 was 1 in 205,233 live births, which was comparable to the data from Europe and the USA. An increase in the concentration of medium-chain acylcarnitines (C8-C12) and determination of «GA2 index» ([C4xC5 x C8xC14]/[C0xC3], which has not been previously used in the screening algorithm) were found to be informative biomarkers for GA2. The «GA2 index» was increased in 5 out of the 6 patients. Five newborns had biallelic mutations in the ETFDH gene (four in the FAD-binding domain), and one newborn had previously undescribed variants in the ETFA gene. At the time of examination, symptoms were present in three newborns (all carriers of the ETFDH mutations). Two patients with a severe form of GA2 (one with a lethal outcome) were homozygous carriers of the c.652G>A (p.Asp218Asn) variant, suggesting an association between this variant and a severe neonatal GA2 phenotype. Thus, mutations in the ETFDH gene may be associated with a more severe phenotype of GA2 than previously estimated. Determination of the «GA2 index» [C4xC5 x C8xC14]/[C0xC3] may increase the effectiveness of biochemical screening for GA2.

Background. The research and study spinal muscular atrophy (SMA 5q) severity modifiers in different patient cohorts remains a crucial task. In practice it is not possible to explain the clinical diversity of SMA 5q only by variations of SMN2 copies. For the c.859G>C variant in exon 7 of SMN2, several studies have described an association with a milder clinical phenotype of SMA due to increased inclusion of exon 7 in the SMN2 gene transcript and generation of more functional SMN protein.

Aim: to explore the modifying effect of the c.859G>C variant in the clinical structure of SMA 5q in Russian patients.

Materials. The search for the c.859G>C p. (Gly287Arg) variant in SMN2 gene was performed in 488 unrelated patients referred for molecular genetic diagnostics of spinal muscular atrophy from 2020 to 2022 to the laboratory of DNA diagnostics in the Research Center for Medical Genetics, Moscow. The control group consisted of 200 DNA samples from residents of the Russian Federation with 2 copies of SMN1 and 2 copies of SMN2.

Methods. Multiplex ligation-dependent probe amplification (MLPA).

Results. The frequency of c.859G>C SMN2 in Russian patients was 0.2%. In summary, it is not possible to assess the effect of c.859G>C as a factor modifying the phenotype of SMA due to the extremely low frequency of this variant.

Specialists working in the field of prenatal diagnosis of chromosomal diseases regularly face the problem of mosaicism. The existence of placenta-limited mosaicism is well known, in which the fetus has a normal chromosomal set, and certain chromosmic abnormalities can be found in the placenta. There is, however, another type - embryonic mosaicism. In this case, a normal chromosomal set can be found in the cells of the placenta, while the fetus has a chromosomal pathology. A variant of mosaicism is also possible, in which different variants of the abnormal karyotype are present in the placenta and in the fetus. This paper examines several clinical cases of embryonic mosaicism identified during prenatal diagnosis of chromosomal abnormalities, discusses possible causes of such results and ways to optimize diagnostic algorithms. The study included five patients who underwent invasive prenatal diagnostics and/or NIPT at the Institute of Obstetrics and Gynecology named after D. Ott in 2012-2023. Diagnosis of chromosomal pathology was performed using standard karyotyping, FISH, CMA, and NIPT. Possible reasons for discordant results and ways to optimize diagnostic algorithms are discussed.

Background. The detection of genetic variants of interest in mosaic disease can be significantly complicated by the low representation of such variants in the biological material taken for analysis. There is a wide range of methodological approaches for the detection of rare genetic variants in clinical and laboratory diagnostics, but not all of them may be available to many laboratories due to various limitations. A method using duplex-specific nuclease followed by Sanger sequencing aims to detect low-representation single-nucleotide genetic variants virtually anywhere in the genome.

Aim: to improve the method of molecular genetic diagnostics of mosaic forms of genetic diseases using duplex-specific nuclease (DSN) on the example of PIK3CA-related overgrowth spectrum (PROS).

Methods. DNA from peripheral blood leukocytes and tissue biopsies was used as a material for the study. To determine the analytical properties of the method, the level of alternative allele representation was modeled by adding DNA samples homozygous for polymorphic and reference variants to the reaction in different ratios.

Results. The minimum reliably detectable level of alternative allele representation was 1.5%. Using the DSN-based method, the PIK3CA genetic variants previously detected on the NGS panel with high coverage in 9 patients with clinical manifestations of PROS were confirmed.