Mitochondrial DNA maintenance disorders in 102 patients from different parts of Russia: Mutational spectrum and phenotypes.

Currently, pathogenic variants in more than 25 nuclear genes, involved in mtDNA maintenance, are associated with human disorders. mtDNA maintenance disorders manifest with a wide range of phenotypes, from severe infantile-onset forms of myocerebrohepatopathy to late-onset forms of myopathies, chronic progressive external ophthalmoplegia, and parkinsonism. This study represents the results of molecular genetic analysis and phenotypes of 102 probands with mtDNA maintenance disorders. So far, this is the largest Russian cohort for this group of diseases. Mutations were identified in 10 mtDNA maintenance genes: POLG (n = 59), DGUOK (n = 14), TWNK (n = 14), TK2 (n = 8), MPV17 (n = 2), OPA3 (n = 1), FBXL4 (n = 1), RRM2B (n = 1), SUCLG1 (n = 1) and TYMP (n = 1). We review a mutation spectrum for the DGUOK and TWNK genes, that can be specific for the Russian population. In 34 patients we measured the blood mtDNA copy number and showed its significant reduction. Novel variants were found in 41 cases, which significantly expands the mutational landscape of mtDNA maintenance disorders.

Mucopolysaccharidosis Type I in the Russian Federation and Other Republics of the Former Soviet Union: Molecular Genetic Analysis and Epidemiology.

Mutations in the IDUA gene cause deficiency of the lysosomal enzyme alpha-l-iduronidase (IDUA), which leads to a rare disease known as mucopolysaccharidosis type I. More than 300 pathogenic variants of the IDUA gene have been reported to date, but not much is known about the distribution of mutations in different populations and ethnic groups due to the low prevalence of the disease. This article presents the results of a molecular genetic study of 206 patients with mucopolysaccharidosis type I (MPS I) from the Russian Federation (RF) and other republics of the former Soviet Union. Among them, there were 173 Russian (Slavic) patients, 9 Tatars, and 24 patients of different nationalities from other republics of the former Soviet Union. Seventy-three different pathogenic variants in the IDUA gene were identified. The common variant NM_000203.5:c.208C>T was the most prevalent mutant allele among Russian and Tatar patients. The common variant NM_000203.5:c.1205G>A accounted for only 5.8% mutant alleles in Russian patients. Both mutations were very rare or absent in patients from other populations. The pathogenic variant NM_000203.5:c.187C>T was the major allele in patients of Turkic origin (Altaian, Uzbeks, and Kyrgyz). Specific own pathogenic alleles in the IDUA gene were identified in each of these ethnic groups. The identified features are important for understanding the molecular origin of the disease, predicting the risk of its development and creating optimal diagnostic and treatment tools for specific regions and ethnic groups.

The novel synonymous variant in LIPA gene affects splicing and causes lysosomal acid lipase deficiency.

Lysosomal acid lipase deficiency (LALD; MIM#278000) is a continuum of autosomal recessive diseases caused by defects in the gene LIPA and historically divided into two phenotypes: severe infantile-onset form called Wolman disease (WD) and childhood/adult-onset form known as cholesteryl ester storage disease (CESD). We report a novel synonymous homozygous variant c.600G > A in LIPA of a patient with LALD. Functional analysis of the patient cDNA and minigene assay revealed this variant as the cause of exonic cryptic splice site activation and 63 b.p. deletion in exon 6. To investigate the impact of this in-frame deletion on protein function, we performed 3D modeling of the human lysosomal acid lipase and showed the alteration of highly conservative region in close proximity to protein active site, which may completely eliminate the enzymatic activity. Using transcript specific real-time quantitative PCR method, we evaluated the relative ratio of the patient's wild type transcript isoform which is significantly reduced and correlates with severe childhood-onset variant of LALD.

The Unique Spectrum of Mutations in Patients with Hereditary Tyrosinemia Type 1 in Different Regions of the Russian Federation.

BACKGROUND: Hereditary tyrosinemia (HT1) is an autosomal recessive disorder characterized by impaired tyrosine catabolism because of fumarylacetoacetate hydrolase deficiency. HT1 is caused by homozygous or compound heterozygous mutations in the FAH gene. The HT1 frequency worldwide is 1:100,000-1:120,000 live births. The frequency of HT1 in the Russian Federation is unknown. AIM: To estimate the spectrum of mutations in HT1 in several ethnic groups of the Russian Federation. MATERIALS AND METHODS: From 2004 to 2017, 43 patients were diagnosed with HT1. The analysis of amino acids and succinylacetone was performed using NeoGram Amino Acids and Acylcarnitines Tandem Mass Spectrometry Kit and a Sciex QTrap 3200 quadrupole tandem mass spectrometer. Bi-directional DNA sequence analysis was performed on PCR products using an ABI Prism 3500. RESULTS: In the Russian Federation, the most common mutation associated with HT1 (32.5% of all mutant alleles) is c.1025C>T (p.Pro342Leu), which is typical for the Chechen ethnic group. Patients of the Yakut, the Buryat, and the Nenets origins had a homozygous mutation c.1090G>C (p.Glu364Gln). High frequency of these ethnicity-specific mutations is most likely due to the founder effect. In patients from Central Russia, the splicing site mutations c.554-1G>T and c.1062+5G>A were the most prevalent, which is similar to the data obtained in the Eastern and Central Europe countries. CONCLUSION: There are ethnic specificities in the spectrum of mutations in the FAH gene in HT1. The Chechen Republic has one of the highest prevalence of HT1 in the world.

[High resolution respirometry in diagnostic of mitochondrial disorders caused by mitochondrial complex I deficiency]. / Respirometriia vysokogo razresheniia v diagnostike mitokhondrial'nykh zabolevanii s narusheniem raboty I kompleksa dykhatel'noi tsepi mitokhondrii.

Complex I (CI) deficiency is one of the most common defects in the OXPHOS system; it represents more than 30% cases of mitochondrial diseases. The group is characterized by clinical and genetic heterogeneity and comprise several nosological forms. The most prevalent phenotypes for CI are LHON and Leigh syndrome. In this study we have analyzed skin fibroblasts from 11 patients with mutations in mtDNA, which cause LHON or Leigh-like phenotypes: m.11778 G>A (n=3), m.3460 A>G (n=2), m.3635 G>A (n=1), m.3308 T>G (n=2), m.3472 T>C (n=1) and 2 patients with earlier unknown substitutions m.3945 C>A and m.14441T>C. High-resolution respirometry (HRR) on the Oxygraph-2k instrument ("Oroboros corp.", Austria) was performed for complex analysis of the mitochondrial respiratory function in intact and permeabilized fibroblasts of patients and healthy controls. Flux control rations in intact cells R/E, (R-L)/E (p<0.05) were raised compared to the control. Rates of R, E, L normalized on the CS were statistically varied between patients and controls. In permeabilized fibroblasts we observed differences in CII/E, Rot/E, R/CII, CI/CII (p<0.05) between groups. These data highlight the dysfunction of the OXPHOS system and particularly CI. Increased citrate synthase level and decreased CI/CII ratio indicate compensatory metabolic response to respiratory chain dysfunction. Our results show applicability of HRR in revealing the biochemical abnormalities of complex I in fibroblasts of patients with LHON and Leigh-like syndrome. We also suggest HRR to be a useful method for inspection of other mutations causing complex I deficiency.

[THE INTERRELATION OF BIOLOGICAL AGE OF THE STUDENTS WITH THE INDICES OF BODY MASS, ITS COMPONENTS, AND THE CONSTITUTIONAL TYPE].

The relationship of biological age with the indices of body mass, body composition, and constitutional type was studied in 832 students aged 18­22 years (302 youths and 530 girls). To determine the biological age, the method of V. P. Voytenko (1981) was used that allowed to establish functional class, rate of aging and health condition. It was found that almost half of the students had poor health associated with the accelerated rate of biological aging. A decline in the proportion of active cell mass and an increase in body fat mass was noted. In 40.6% of students with normal values of body mass index, excessive amount of body fat was determined by bioimpedance method. 62.2% of the students with an accelerated rate of biological aging had an increased content of a fat component in the body.