Эпигенетика болезни Фридрейха: метилирование области экспансии (GAA)n-повторов гена FXN

Background: Friedreich’s disease (FD) is the most common hereditary ataxia. It is associated, most frequently, with homozygous GAA repeats expansion in intron 1 of the FXN gene. Methylation of the FXN gene can play an important role in the pathogenesis of FD. Aims: to study methylation pattern in CpG sites flanking GAA-expansion in intron 1 of the FXN gene in patients with FD and their heterozygous relatives as well as its relationship with clinical features. Materials and methods: We studied DNA samples from patients with FD (n=18), their relatives carrying heterozygous GAA expansion (n=12), and control group (n=15). Pattern of methylation was studied by direct sequencing of DNA regions after bisulphide processing. Results: We analyzed 18 CpG sites in the UP-GAA region of the gene (before GAA-repeats) and 12 CpG sites in the DOWN-GAA region (after GAA-repeats). In the UP-region, the mean methylation level of CpG sites in FD patients was higher compared to controls (n=15) (р0.05), while in the DOWN-region there was a decrease of mean methylation level in FD compared to controls (р0.05). Analysis of methylation level in different CpG sites in the UP-GAA region revealed hypermethylation for 15 of 18 CpG-sites as compared to controls (р0.05). The most significant differences in methylation level in the UP-GAA region were seen for CpG sites 50−54, 57 and 58. In contrast, in the DOWN-GAA region almost all CpG sites were fully methylated in the control group, while in FD patients methylation was significantly lower (р0.05). We revealed positive correlation of mean methylation level and more expanded allele length for the UP-GAA region in FD (r=0.63; p=0.03), and no correlations for the DOWN-GAA region. In heterozygous carriers we observed an analogous positive correlations in the UP-GAA region for CpG site 50 (r=0.77; p=0.04), while in the DOWN-GAA region there was inverse correlation of methylation with GAA repeat number in the expanded allele (r=-0.83, p=0.02). Negative correlation was found between the hypermethylation of some CpG-sites in the UP-GAA region and age of the disease onset (p0.05). Conclusion: We revealed hypermethylation in the UP-GAA region and hypomethylation in the DOWN-GAA region in patients with FD compared to controls and correlations of methylation level with the GAA expansion length and age of disease onset.Обоснование. Болезнь Фридрейха (БФ) ― самая частая форма среди наследственных атаксий, в большинстве случаев связанная с гомозиготной экспансией GAA-повторов в 1-м интроне гена FXN. Метилирование данного гена может играть большую роль в патогенезе БФ. Цель — изучить паттерн метилирования CpG-сайтов, фланкирующих область GAA-повторов гена FXN у пациентов с БФ и их родственников с гетерозиготным носительством GAA-экспансии, а также его взаимосвязь с клиническими особенностями заболевания. Методы. Исследованы образцы ДНК пациентов с БФ (n=18), их родственников с гетерозиготным носительством GAA-экспансии (n=12) и здоровых добровольцев группы контроля (n=15). Паттерн метилирования определяли методом прямого секвенирования после бисульфитной обработки. Результаты. Всего проанализировано 18 CpG-сайтов в UP-GAA области гена (до GAA-повторов) и 12 сайтов в DOWN-GAA области (после GAA-повторов). В UP-GAA области наблюдался более высокий уровень метилирования CpG-сайтов для БФ по сравнению с контрольной группой (р0,05), а в DOWN-GAA области ― снижение среднего уровня метилирования для БФ по сравнению с контролем (р0,05). Анализ степени метилирования UP-GAA области у пациентов с БФ по сравнению с контролем выявил гиперметилирование по 15 CpG-сайтам из 18 (р0,05). Наибольшие различия в уровне метилирования в UP-GAA области наблюдались для CpG-сайтов 50–54, 57 и 58. Напротив, в DOWN-GAA области в контрольной группе практически все CpG-сайты были метилированы полностью, а в группе БФ уровень метилирования был статистически значимо меньше (р0,05). Выявлена прямая корреляция усредненного процента метилирования для UP-GAA области с длиной более длинного экспандированного аллеля при БФ (r=0,63; p=0,03) и отсутствие корреляций для DOWN-GAA области. У гетерозиготных носителей выявлена аналогичная прямая корреляция в UP-GAA области для CpG-сайта 50 (r=0,77; p=0,04), тогда как в DOWN-GAA области наблюдалась обратная зависимость метилирования от числа GAA-повторов в экспандированном аллеле (r=-0,83, p=0,02). Выявлена отрицательная корреляционная связь между гиперметилированием отдельных CpG-сайтов в UP-GAA области и возрастом дебюта заболевания (р0,05). Заключение. В работе выявлено гиперметилирование UP-GAA области и гипометилирование DOWN-GAA области у пациентов с БФ по сравнению с контрольной группой, что определяется длиной GAA-экспансии и оказывает непосредственное влияние на возраст дебюта заболевания

Generation of induced pluripotent stem cell line, ICGi007-A, by reprogramming peripheral blood mononuclear cells from a patient with Huntington's disease

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease caused by mutation in the HTT gene encoding HTT protein. The mutant protein leads to the neuronal death through dysregulation of multiple cellular processes. HD human induced pluripotent stem cells (iPSCs) represent a useful and valid model for the disease study. iPSC line from HD patient with 47 CAG repeats in HTT was generated from blood mononuclear cells by non-integrating episomal vectors. The iPSC line retained the mutation, expressed pluripotency markers, had a normal karyotype and displayed in vitro differentiation to the three germ layers.Resource table.Unlabelled TableUnique stem cell lines identifierICGi007-AAlternative name(s) of stem cell line47Q-3LfInstitutionFederal Research Center Institute of Cytology and Genetics, the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, RussiaContact information of distributorElena V. Grigor'[email protected] of cell linesiPSCOriginHumanAdditional origin infoAge: 27Sex: FEthnicity: CaucasianCell SourcePeripheral blood mononuclear cellsClonalityClonalMethod of reprogrammingTransgene free episomal plasmid vectorsGenetic ModificationYESType of ModificationHereditaryAssociated diseaseHuntington's diseaseGene/locusHTT/4p16.3Method of modificationN/AName of transgene or resistanceN/AInducible/constitutive systemN/ADate archived/stock dateDecember 2017Cell line repository/bankhttps://hpscreg.eu/cell-line/ICGi007-AEthical approvalThe generation of iPSC line from cells donated by patient with informed consent was reviewed and approved by “Center of New Medical Technology in Akademgorodok” (protocol No. 21

Substitution of Met-38 to Ile in γ-synuclein found in two patients with amyotrophic lateral sclerosis induces aggregation into amyloid

α-, β-, and γ-Synuclein are intrinsically disordered proteins implicated in physiological processes in the nervous system of vertebrates. α-synuclein (αSyn) is the amyloidogenic protein associated with Parkinson’s disease and certain other neurodegenerative disorders. Intensive research has focused on the mechanisms that cause αSyn to form amyloid structures, identifying its NAC region as being necessary and sufficient for amyloid assembly. Recent work has shown that a 7-residue sequence (P1) is necessary for αSyn amyloid formation. Although γ-synuclein (γSyn) is 55% identical in sequence to αSyn and its pathological deposits are also observed in association with neurodegenerative conditions, γSyn is resilient to amyloid formation in vitro. Here, we report a rare single nucleotide polymorphism (SNP) in the SNCG gene encoding γSyn, found in two patients with amyotrophic lateral sclerosis (ALS). The SNP results in the substitution of Met38 with Ile in the P1 region of the protein. These individuals also had a second, common and nonpathological, SNP in SNCG resulting in the substitution of Glu110 with Val. In vitro studies demonstrate that the Ile38 variant accelerates amyloid fibril assembly. Contrastingly, Val110 retards fibril assembly and mitigates the effect of Ile38. Substitution of residue 38 with Leu had little effect, while Val retards, and Ala increases the rate of amyloid formation. Ile38 γSyn also results in the formation of γSyn-containing inclusions in cells. The results show how a single point substitution can enhance amyloid formation of γSyn and highlight the P1 region in driving amyloid formation in another synuclein family member