Hereditary spastic paraplegia (HSP) comprises a heterogeneous group of neurodegenerative disorders, it share common symptom - of progressive lower spastic paraparesis. The most common autosomal dominant (AD) forms of HSP are SPG4 (SPAST gene) and SPG3 (ATL1 gene). In the current research we investigated for the first time the distribution of pathogenic mutations in SPAST and ATL1 genes within a large cohort of Russian HSP patients (122 probands; 69 famillial cases). We determined the frequencies of genetic abnormalities using Sanger sequencing, multiplex ligation-dependent probe amplification (MLPA), and Next Generation Sequencing (NGS) of targeted gene panels. As a result, SPG4 was diagnosed in 30.3% (37/122) of HSP cases, where the familial cases represented 37.7% (26/69) of SPG4. In total 31 pathogenic and likely pathogenic variants were detected in SPAST, with 14 new mutations. Among all detected SPAST variants, 29% were gross deletions and duplications. The proportion of SPG3 variants in Russian cohort was 8.2% (10/122) that were all familial cases. All 10 detected ATL1 mutations were missense substitutions, most of which were in the mutational hot spots of 4, 7, 8, 12 exons, with 2 novel mutations. This work will be helpful for the populational genetics of HSP understanding.

Phenylalanine hydroxylase (PAH) deficiency is responsible for most cases of phenylketonuria (PKU). Furthermore, numerous studies on BH4-sensitive PAH deficiency have been conducted. To date, BH4, a cofactor of PAH, has not been used to treat PKU in Russia.Genotype data of patients with PKU can be used to predict their sensitivity to BH4 therapy. A cohort of 2579 patients with PKU from Russia was analyzed for 25 common PAH gene mutations using custom allele-specific multiplex ligation-dependent probe amplification-based technology. A mutation detection rate of 84.1% chromosomes was accomplished. Both pathogenic alleles were identified in 73.1% of patients. The most frequent pathogenic variants were p.Arg408Trp (50.9%), p.Arg261Gln (5.3%), p.Pro281Leu (3.5%), IVS12+1G>A (3.1%), IVS10-11G>A (2.6%), and p.Arg158Leu (2.4%). The exact boundaries of a PAH exon 5 deletion were defined as EX5del4154ins268 (c.442-2913_509+1173del4154ins268). Severe phenotypes prevailed in the cohort, and classical PKU was observed in 71.8% cases. Due to the genotype-based prediction, 55.9% of the probands were non-responders to the BH4-treatment, and 20.2% were potential responders. Analysis of genotype data is useful to predict BH4 response in PKU patients. The high rate of non-responders among Russian patients was due to the high allele frequency of severe PAH mutations.

Phenylketonuria is an inherited disease caused by mutations in the phenylalanine hydroxylase gene PAH. Different PAH pathogenic variants occur in different ethnic groups with various frequencies and the incidence of the disease itself varies from country to country. In the Caucasus region of Russia, some ethnoses are geographically and culturally isolated from each other. The tradition of monoethnic marriages may cause decreased genetic variability in those populations. In the Karachay-Cherkess Republic (Russia), the highest incidence of phenylketonuria in the world has been detected (1:850 newborns) in the region and 1:332 among the titular nation Karachays. Here, we showed that this phenomenon is due to the widespread prevalence of the p.Arg261* variant. Its allele frequency among Karachay patients with PKU was 68.4% and the carrier frequency in Karachays was 1:16 healthy individuals. PAH haplotype analysis showed a unique common origin. The founder haplotype and mutation “age” were estimated by analyzing the linkage disequilibrium between p.Arg261* and extragenic short tandem repeat loci. The p.Arg261* variant occurred in the Karachays population 10.2 ± 2.7 generations ago (275 ± 73 years) and its spread occurred in parallel with the growth of the population.

Pathogenic variants in the RPE65 gene cause the only known form of inherited retinal degenerations (IRDs) that are prone to gene therapy. The current study is aimed at the evaluation of the prevalence of RPE65-associated retinopathy in the Russian Federation, the characterization of known variants in the RPE65 gene, and the establishment of the specificities of the mutation spectrum in Russian patients. Methods: The analysis was carried out on blood samples obtained from 1053 non-related IRDs patients. The analysis, which consisted of 211 genes, was carried out based on the method of massive parallel sequencing (MPS) for all probands. Variant validation, as well as biallelic status verification, were carried out using direct automated Sanger sequencing. The number of copies of RPE65 exons 1–14 was analyzed with quantitative MLPA using an MRC-Holland SALSA MLPA probemix. Results: Out of 1053 non-related patients, a molecular genetic diagnosis of IRDs has been confirmed in 474 cases, including 25 (5.3%) patients with RPE65-associated retinopathy. We detected 26 variants in the RPE65 gene, nine of which have not been previously described in the literature. The most common mutations in the Russian population were c.304G>T/p.(Glu102*), c.370C>T/p.(Arg124*), and c.272G>A/p.(Arg91Gln), which comprised 41.8% of all affected chromosomes. Conclusions: The current study shows that pathogenic variants in the RPE65 gene contribute significantly to the pathogenesis of IRDs and comprise 5.3% of all patients with a confirmed molecular genetic diagnosis. This study allowed for the formation of a cohort for target therapy of the disorder; such therapy has already been carried out for some patients.

CFTR modulators have significantly affected the prognosis for cystic fibrosis, improving the clinical course in most patients with the F508del variant and several other CFTR gene variants. The presence of complex alleles, including more than one variant in the cis position, can change the properties of the protein and the efficacy of modulators. Objective: We aimed to describe the efficacy of CFTR modulators in the treatment of two siblings with the c.[1521_1523delCTT;1399C>T];[54-5940_273+10250del21kb] (L467F;F508del/CFTRdele2,3) genotype in clinical practice and in vitro. This article presents the clinical presentation and results of CFTR channel function assessment and personalized selection of CFTR modulators in monochorionic diamniotic twins with cystic fibrosis and the L467F;F508del/CFTRdele2,3 genotype. This is the first demonstration of the efficacy of a new CFTR modulator in patients with a complex allele and a class I variant in the genotype. The obtained results may be useful for choosing treatment strategies for patients with a complex allele and a class I variant in the genotype.

The objective is to study the occurrence of common genetic factors of male infertility in men with reproductive problems, their combinations and spermatological characteristics. Materials and methods . 393 men with infertility in marriage were examined. According to the results of the cytogenetic study, the sample is divided into 3 groups: 135 men with numerical sex chromosome abnormalities; 58 male patients with a balanced structural rearrangement; 200 men with normal karyotype. Y chromosome microdeletions, CFTR gene mutations and CAG-repeats polymorphism of AR gene were analyzed. Results . The Y-chromosome microdeletions partially AZFc deletions were detected in 13 % male patients with sex chromosome abnormalities. A combination of chromosomal abnormalities with AZF deletions and/or CFTR gene mutations and long CAG repeats of AR gene was found in 19 % infertile men with balanced chromosome rearrangements. Infertile men with normal male karyotype presented the frequency of common genetic factors of male infertility was almost 2 times higher than the combined frequency of these factors in groups of patients with chromosomes abnormalities. Azoospermia in men with normal karyotype and patients with chromosome abnormalities was diagnosed with the same frequency (58 %). In all men who have identified the presence of two or more genetic factors of male infertility, severe forms of pathozoospermia (azoospermia and severe oligozoospermia) were found. Conclusion . The combination of genetic factors of male infertility is accompanied by severe forms of pathozoospermia that indicates a possible additive effect of negative effect on spermatogenesis and male fertility.