The GJB2 (Cx26) gene pathogenic variants are associated with autosomal recessive deafness type 1A (DFNB1A, OMIM #220290). Direct sequencing of the GJB2 gene among 165 hearing-impaired individuals living in the Baikal Lake region of Russia identified 14 allelic variants: pathogenic/likely pathogenic—nine variants, benign—three variants, unclassified—one variant, and one novel variant. The contribution of the GJB2 gene variants to the etiology of hearing impairment (HI) in the total sample of patients was 15.8% (26 out of 165) and significantly differed in patients of different ethnicity (5.1% in Buryat patients and 28.9% in Russian patients). In patients with DFNB1A (n = 26), HIs were congenital/early onset (92.3%), symmetric (88.5%), sensorineural (100.0%), and variable in severity (moderate—11.6%, severe—26.9% or profound—61.5%). The reconstruction of the SNP haplotypes with three frequent GJB2 pathogenic variants (c.-23+1G>A, c.35delG or c.235delC), in comparison with previously published data, supports a major role of the founder effect in the expansion of the c.-23+1G>A and c.35delG variants around the world. Comparative analysis of the haplotypes with c.235delC revealed one major haplotype G A C T (97.5%) in Eastern Asians (Chinese, Japanese and Korean patients) and two haplotypes, G A C T (71.4%) and G A C C (28.6%), in Northern Asians (Altaians, Buryats and Mongols). The variable structure of the c.235delC-haplotypes in Northern Asians requires more studies to expand our knowledge about the origin of this pathogenic variant.

The populations of the Arctic Ocean coast in Eastern Siberia (Russia) are represented by a multicultural conglomerate of peoples of different origins: Paleo-Asiatic (Chukchi), Uralic (Yukaghirs), Tungusic (Evenks, Evens), Turkic (Yakuts, Dolgans), and Slavic (Russian explorers), who inhabited this territory during various historical periods. However, among the modern Arctic populations there are still “white spots”, such as people of the small village of “Russkoe Ust’ye”, who still have not been thoroughly studied. The main population consists of so called Russian old-settlers—the Russkoustinians. They traditionally distinguish their lineages into three groups identified by their time of settlement. First are the “Pomors”—who according to their legends are considered as the descendants of the first European colonists of the Age of Discovery, who settled the eastern shores of the Arctic Ocean in the 16th century before the inclusion of this territory in the Russian Empire in the early 17th century. Second are the “Cossacks”—who reached the Arctic during explorations of Siberia. The last are the “Zashiversk”—who arrived after the abolition of their hometown. In order to test these hypotheses, we analyzed modern family name diversity based on information on 62 individuals from 36 questionnaires. The analysis revealed that the “Pomors” lineages were presented in five families (43.5%), the “Cossacks” in one family (6.5%), and the “Zashiversk” in 37.1% of families. This fact indicates a probability that this village was founded by Russian Pomors who arrived there by the Northern Sea Routes before the official East Siberian colonization period.

Приведены результаты анализа ассоциаций вариантов гена babA Helicobacter pylori с течением гастродуоденальных заболеваний (эрозивный и хронический гастрит) у пациентов в Якутии. Показано, что вариант гена babA2 преобладал у пациентов с эрозивными гастритами по сравнению с пациентами с хроническим гастритом, в то время как вариант гена babAI чаще встречался у пациентов с хроническим гастритом, чем у пациентов с эрозивным гастритом. Кроме того, было показано, что у пациентов-мужчин чаще встречался вариант гена babA2, чем у женщин, что свидетельствует о том, что инфицирование мужчин штаммом H. pylori с вариантом гена babA2 является дополнительным фактором риска более тяжелого течения гастродуоденальных...

Pathogenic variants of mitochondrial tRNA genes remain poorly understood in the context of the study of the etiology of hearing loss, despite the fact that they are one of the important causes of syndromic and non-syndromic hearing impairment as well as aminoglycoside-induced hearing loss. In this work, we searched for pathogenic variants of the mtDNA MT-TS1 gene in patients with hearing impairments in Buryatia. One rare variant m.7445A>C was found in the MT-TS1 gene out of five investigated variants in one patient (1/165; 0.6%). This variant is localized in the coding region of two genes the MT-CO1 (H-chain) and MT-TS1 (L-chain), but on different mtDNA chains. However, a pathogenetic role for the m.7445A>C substitution has been shown for the MT-TS1 gene, but not for the MT-CO1 gene. In databases, the m.7445A>C variant is associated with non-syndromic hearing loss, including those caused by aminoglycoside antibiotics. A comparative genotype-phenotypic analysis of our case and four cases with m.7445A>C of the MT-TS1 gene described earlier in the literature showed that hearing loss in all cases is not congenital, but at the same time varies in severity with low penetrance. The results obtained indicate the involvement of other modulating factors in the clinical manifestation of hearing impairment associated with this variant. Thus, further study of rare variants of MT-TS1 gene will contribute to our understanding of the pathogenetic mechanisms of mitochondrial forms of hearing loss. Keywords: non-syndromic hearing loss, mtDNA, MT-TS1, m.7445A>C, Buryatia.

In the world the role of pathogenic variants of the MYO15A gene in the etiology of hearing loss has not been sufficiently studied, since the large size of the gene (66 exons, 71 kb) suggests the search for pathogenic variants using NGS technologies, which are not yet sufficiently used in routine practice. In this regard, it is relevant to study the role of pathogenic variants of the MYO15A gene in the etiology of non-syndromic forms of hearing impairments. The purpose of this work is to describe the rare pathogenic variant c.7636C>T p.(Gln2546*) in the MYO15A gene, found in a homozygous state in two siblings with prelingual profound sensorineural hearing loss from a Buryat family. Previously, this variant was found only in one patient in a compound-heterozygous state with another nonsense variant in the MYO15A gene in Brazil and described as pathogenic. Detection of variant c.7636C>T p.(Gln2546*) in a homozygous state in Buryat siblings may indicate either a rare case of endogamous marriage or a wider distribution of this variant in the Lake Baikal region. Keywords: autosomal recessive deafness (DFNB3), MYO15A gene, variant c.7636C>T p.(Gln2546*), Republic of Buryatia.

In the previous study, we found a high prevalence of the m.1555A>G variant of the MT-RNR1 gene, which causes mitochondrial hearing loss (OMIM 561000) among deaf patients living in the Baikal Lake region. In this regard, in the present study, a genotype-phenotypic analysis of the hearing function in individuals with the m.1555A>G variant was carried out in the discovered Siberian region. Clinical and audiological analysis was performed in 48 people with this mitochondrial variant, whose average age was 51.3±15.5 years. The obtained genotype-phenotypic data are consistent with previously conducted studies of the features of the auditory function in individuals with m.1555A>G, which note incomplete penetrance of the manifestation of the pathological phenotype. Of particular interest in our cohort are three cases of mixed hearing loss, including both sensorineural (inner ear defect) and conductive (middle ear defect) components. We do not exclude the possibility that the detected clinical signs may be a consequence of systemic damage to the hearing organ in this mitochondrial variant. On the other hand, the detected cases may be associated with a cross-pathological effect caused by another form of a less common or rare disease, which requires further molecular genetic studies.