Genetic Landscape and Clinical Features of Hyperphenylalaninemia in North Ossetia-Alania: High Frequency of P281L and P211T Genetic Variants in the PAH Gene.

This study, conducted in the Republic of North Ossetia-Alania (RNOA), aimed to explore the genetic landscape of hyperphenylalaninemia (HPA) and phenylketonuria (PKU) in the Ossetian population using data from newborn screening (NBS). Through comprehensive molecular genetic analysis of 29 patients with HPA from diverse ethnic backgrounds, two major genetic variants in the PAH gene, P281L and P211T, were identified, constituting 50% of all detected pathogenic alleles in Ossetian patients. Remarkably, these variants exhibited an exceptionally high frequency in the Ossetian population, surpassing global prevalence rates. This study unveiled a notable prevalence of mild forms of HPA (78%), underscoring the importance of genetic counseling for carriers of pathogenic variants in the PAH gene. Moreover, the findings emphasized the necessity for ongoing monitoring of patients with mild forms, as they may lack significant symptoms for diagnosis, potentially impacting offspring. Overall, this research offers valuable insights into the genetic landscape of HPA and PKU in the Ossetian population.

Epidemiology of PAX6 Gene Pathogenic Variants and Expected Prevalence of PAX6-Associated Congenital Aniridia across the Russian Federation: A Nationwide Study.

This study investigates the distribution of PAX6-associated congenital aniridia (AN) and WAGR syndrome across Russian Federation (RF) districts while characterizing PAX6 gene variants. We contribute novel PAX6 pathogenic variants and 11p13 chromosome region rearrangements to international databases based on a cohort of 379 AN patients (295 families, 295 probands) in Russia. We detail 100 newly characterized families (129 patients) recruited from clinical practice and specialized screening studies. Our methodology involves multiplex ligase-dependent probe amplification (MLPA) analysis of the 11p13 chromosome, PAX6 gene Sanger sequencing, and karyotype analysis. We report novel findings on PAX6 gene variations, including 67 intragenic PAX6 variants and 33 chromosome deletions in the 100 newly characterized families. Our expanded sample of 295 AN families with 379 patients reveals a consistent global PAX6 variant spectrum, including CNVs (copy number variants) of the 11p13 chromosome (31%), complex rearrangements (1.4%), nonsense (25%), frameshift (18%), and splicing variants (15%). No genetic cause of AN is defined in 10 patients. The distribution of patients across the Russian Federation varies, likely due to sample completeness. This study offers the first AN epidemiological data for the RF, providing a comprehensive PAX6 variants spectrum. Based on earlier assessment of AN prevalence in the RF (1:98,943) we have revealed unexamined patients ranging from 55% to 87%, that emphases the need for increased awareness and comprehensive diagnostics in AN patient care in Russia.

Genetic Heterogeneity of X-Linked Ichthyosis in the Republic of North Ossetia-Alania, Case Series Report.

North Caucasus has always been a residence of a lot of different authentic ethnic groups speaking different languages and still living their traditional lifestyle. The diversity appeared to be reflected in the accumulation of different mutations causing common inherited disorders. X-linked ichthyosis represents the second most common form of genodermatoses after ichthyosis vulgaris. Eight patients from three unrelated families of different ethnic origin, Kumyk, Turkish Meskhetians, and Ossetian, with X-linked ichthyosis from the North Caucasian Republic of North Ossetia-Alania were examined. NGS technology was implied for searching for disease-causing variants in one of the index patients. Known pathogenic hemizygous deletion in the short arm of chromosome X encompassing the STS gene was defined in the Kumyk family. A further analysis allowed us to establish that likely the same deletion was a cause of ichthyosis in a family belonging to the Turkish Meskhetians ethnic group. In the Ossetian family, a likely pathogenic nucleotide substitution in the STS gene was defined; it segregated with the disease in the family. We molecularly confirmed XLI in eight patients from three examined families. Though in two families, Kumyk and Turkish Meskhetian, we revealed similar hemizygous deletions in the short arm of chromosome X, but their common origin was not likely. Forensic STR markers of the alleles carrying the deletion were defined to be different. However, here, common alleles haplotype is hard to track for a high local recombination rate. We supposed the deletion could arise as a de novo event in a recombination hot spot in the described and in other populations with a recurrent character. Defined here are the different molecular genetic causes of X-linked ichthyosis in families of different ethnic origins sharing the same residence place in the Republic of North Ossetia-Alania which could point to the existing reproductive barriers even inside close neighborhoods.

Hereditary etiology of non-syndromic sensorineural hearing loss in the Republic of North Ossetia-Alania.

More than 50% of congenital hearing loss is hereditary, in which the majority form is non-syndromic. In this study we estimate the most prevalent pathogenic genetic changes in an Ossetian cohort of patients. This is useful for local public health officials to promote genetic counseling of affected families with regard to high allele frequencies of prevalent pathogenic variants and assortative mating in the community of people with hearing loss. In this study, genetic heterogeneity of hereditary non-syndromic sensorineural hearing loss (NSNHL) in a cohort of 109 patients and an assessment of the frequency of two GJB2 gene pathogenic variants in a cohort of 349 healthy individuals from the populations of the Republic of North Ossetia-Alania (RNO-Alania) were assessed. The molecular genetic cause of NSNHL in the GJB2 gene in RNO-Alania was confirmed in ~30% of the cases, including ~27% in Ossetians. In Russian patients, the most frequent variant is GJB2:c.35delG (~83%). The GJB2:c.358_360delGAG variant was found to be the most frequent among Ossetians (~54%). Two genetic variants in GJB2, c.35delG and c.358_360delGAG, accounted for 91% of GJB2 pathogenic alleles in the Ossetian patients. A search for large genome rearrangements revealed etiological cause in two Ossetian patients, a deletion at the POU3F4 gene locus associated with X-linked hearing loss (type DFNX2). In another Ossetian patient, a biallelic pathogenic variant in the MYO15A gene caused hearing loss type DFNB3 was identified, and in one Russian family a heterozygous MYH14 gene variant associated with dominant NSNHL was found. Thus, the informative value of the diagnosis was ~37% among all patients with NSNHL from RNO-Alania and ~32% among the Ossetians. These estimates correspond to the literature data on the fraction of recessive genetic forms of hearing loss within the affected population. The importance of this study consists not only in the estimation of the most prevalent pathogenic genetic changes in the Ossetian cohort of patients which could be useful for the public health but also in the genetic counselling of the affected families with regard to the high allele frequencies of revealed pathogenic variants as well as to the assortative mating in community of people with hearing loss.

Clinical Presentation of the c.3844T>C (p.Trp1282Arg, W1282R) Variant in Russian Cystic Fibrosis Patients.

The goal was to study the phenotypic manifestations of c.3844T>C (p.Trp1282Arg, W1282R) variant, a CF-causing mutation, in patients from the Russian Federation. Clinical manifestations and complications (the age at CF diagnosis, sweat test, pancreatic status, lung function, microbial infection, body mass index (BMI), the presence of meconium ileus (MI), diabetes, and severe liver disease) were compared in four groups: group 1-patients carrying c.3844T>C and severe class I or II variant in trans; group 2-3849+10kbC>T/F508del patients; group 3-F508del/F508del patients; and group 4-patients with W1282R and "mild" variant in trans. Based on the analyses, W1282R with class I or II variant in trans appears to cause at least as severe CF symptoms as F508del homozygotes as reflected in the early age of diagnosis, high sweat chloride concentration, insufficient pancreatic function, and low lung function, in contrast to 3849+10kbC-T/F508del compound heterozygotes having milder clinical phenotypes. The W1282R pathogenic variant is seemed to lead to severe disease phenotype with pancreatic insufficiency similarly to the F508del homozygous genotype.

Comprehensive genotyping reveals novel CFTR variants in cystic fibrosis patients from the Russian Federation.

Single nucleotide variants are represented as lines. The height of the line corresponds to the allele frequency. Gross chromosomal copy number variations are shown as arrows. Color corresponds to the mutation type. Complex alleles represented with a clip. Previously reported variants are located above the schematic gene representation. Their names are presented in Table 1 in main text. Novel variants are depicted beneath the schematic gene representation.

Extracellular GC-rich DNA activates TLR9- and NF-kB-dependent signaling pathways in human adipose-derived mesenchymal stem cells (haMSCs).

INTRODUCTION: The content of GC-rich ribosomal repeats (rDNA) in cell-free DNA (cfDNA) of patients with various diseases is several times higher as compared with genomic DNA (gDNA) and cfDNA of healthy donors. rDNA may act as Toll-like receptor 9 (TLR9) ligands and affect human adipose-derived mesenchymal stem cells (haMSCs). Here we explore effects of human cfDNAs and model rDNA fragments on cultured haMSCs. AREAS COVERED: Both cfDNAs and cloned rDNA stimulate expression of TLR9 (qRT-PCR). Treatment with cloned rDNA leads to an increase in the number of TLR9(+) cells (FACS), expression levels for both TLR9 and Myd88, the translocation of nuclear factor-kappa B to the nuclei and up-regulation of TNFα and IL-10 cytokines (ELISA). As shown by an analysis of γH2AX-foci and MTT test, the preconditioning of haMSCs with cloned rDNA fragment increases the resistance of these cells to irradiation at 2Gy, while the treatments with control gDNA did not stimulate either TLR9- or NF-kB-dependent signaling pathways. EXPERT OPINION: GC-rich sequences present in cfDNA stimulate endogenous stems cells when body is exposed to adverse conditions. GC-rich fragments of human DNA may be used for preconditioning of therapeutic MSCs aiming at an increase in their survival in the ailing body.

Genetic analysis of autosomal recessive osteopetrosis in Chuvashiya: the unique splice site mutation in TCIRG1 gene spread by the founder effect.

The rare malignant disorder autosomal recessive osteopetrosis (OPTB) is one of the most prevalent autosomal recessive diseases in the Chuvash Republic of Russia. The purpose of this study was to determine the underlying molecular cause of osteopetrosis in Chuvashiya and to reveal the factors causing the unusual high frequency of the disease in this region. Having assumed a founder effect, we performed linkage disequilibrium (LD) mapping of the OPTB locus at the TCIRG1 region and found a unique splice site mutation c.807+5G>A in all Chuvashian OPTB patients studied. We then analyzed the mutational change in mRNA and detected an intron insertion within the mutant transcript, resulting in a frameshift and premature stop-codon formation (p.Leu271AspfsX231). A decreased expression of the mutant transcript was also detected, which may have been the result of nonsense-mediated decay. Real-time qPCR and MLPA melting curve analysis-based systems were designed and used for c.807+5G>A mutation screening. In addition to analyzing the gene frequency in Chuvashiya, we also estimated three other populations in the Volga-Ural region (Mari, Udmurt and Bashkir). We found a 1.68% prevalence in Chuvashiya (calculated disease frequency, 1/3500 newborns) and a 0.84% in the Mari population (1/14 000 newborns). The haplotype analysis revealed that all OPTB cases in Chuvashians and Marians originated from a single mutational event and the age of the mutation in Chuvashians was estimated to be approximately 890 years.

Conversion and compensatory evolution of the gamma-crystallin genes and identification of a cataractogenic mutation that reverses the sequence of the human CRYGD gene to an ancestral state.

We identified a mutation in the CRYGD gene (P23S) of the gamma-crystallin gene cluster that is associated with a polymorphic congenital cataract that occurs with frequency of approximately 0.3% in a human population. To gain insight into the molecular mechanism of the pathogenesis of gamma-crystallin isoforms, we undertook an evolutionary analysis of the available mammalian and newly obtained primate sequences of the gamma-crystallin genes. The cataract-associated serine at site 23 corresponds to the ancestral state, since it was found in CRYGD of a lower primate and all the surveyed nonprimate mammals. Crystallin proteins include two structurally similar domains, and substitutions in mammalian CRYGD protein at site 23 of the first domain were always associated with substitutions in the structurally reciprocal sites 109 and 136 of the second domain. These data suggest that the cataractogenic effect of serine at site 23 in the N-terminal domain of CRYGD may be compensated indirectly by amino acid changes in a distal domain. We also found that gene conversion was a factor in the evolution of the gamma-crystallin gene cluster throughout different mammalian clades. The high rate of gene conversion observed between the functional CRYGD gene and two primate gamma-crystallin pseudogenes (CRYGEP1 and CRYGFP1) coupled with a surprising finding of apparent negative selection in primate pseudogenes suggest a deleterious impact of recently derived pseudogenes involved in gene conversion in the gamma-crystallin gene cluster.

Human hair growth deficiency is linked to a genetic defect in the phospholipase gene LIPH.

The molecular mechanisms controlling human hair growth and scalp hair loss are poorly understood. By screening about 350,000 individuals in two populations from the Volga-Ural region of Russia, we identified a gene mutation in families who show an inherited form of hair loss and a hair growth defect. Affected individuals were homozygous for a deletion in the LIPH gene on chromosome 3q27, caused by short interspersed nuclear element-retrotransposon-mediated recombination. The LIPH gene is expressed in hair follicles and encodes a phospholipase called lipase H (alternatively known as membrane-associated phosphatidic acid-selective phospholipase A1alpha), an enzyme that regulates the production of bioactive lipids. These results suggest that lipase H participates in hair growth and development.