Cell mosaicism is found in biological systems much more often than clinically identified forms of the disease, in some cases, "erased forms” or "normal variants” are phenotypic manifestations of mosaicism. Some diseases, difficult for a clinical diagnosis, such as ataxia-telangiectasia, are based on cell mosaicism. This work is aimed to study DNA repair disorders in the cell lines of dermal fibroblasts isolated from skin biopsies of 5 patients with a clinically diagnosed ataxia-telangiectasia. In the obtained cell lines, the method of indirect immunofluorescence was used to determine the number, intensity, focus area pATMSer1981 and 53BP1, as well as the number of cells with the active form of the ATM kinase. The mosaic pattern of malfunctioning of the active form of the ATM kinase, phospho-ATM Ser1981, was revealed at different time intervals after exposure to ionizing radiation at a dose of 2 Gy. Significant differences were found between the number of ATMSer1981 and 53BP1 foci, the fluorescence intensity and their area in the cells of patients with ataxia-telangiectasia and healthy donors. The results of this work can be used in the diagnosis of ataxia-telangiec-tasia and determining the degree of impairment of the functional activity of the ATM gene.

Several parameters representing the clinical diversity of Parkinson's disease (PD), including severity, phenotypes, cognitive decline, anxiety and depression were analyzed to examine the link with interleukin-1β (IL-1β), the interleukin-1 receptor antagonist (IL-1RA), IL-6, IL-10, and tumor necrosis factor-α (TNFα) and also to determine the relationship between levels of these factors in serum and cerebrospinal fluid (CSF). Significantly elevated serum IL-1β and IL-6 and reduced IL-1RA levels were found in the PD group. In CSF and serum, inflammatory factors behaved differently, with increased CSF TNFα indicating rapid PD progression, and increased IL-1β in serum. A low level of IL-6 was associated with a longer duration of PD. Anxiety, depression, non-tremor phenotype and late-onset PD correlated with a high serum level of IL-10. The serum TNFα level was lower in PD patients with mild cognitive impairment compared to controls. Serum IL-1β, IL-6 and IL-10 levels correlated with CSF markers.

Cockayne syndrome is a rare autosomal recessive disease described in the 1930s by E.A. Cockayne. Patients suffer from cachectic dwarfism (when the weight is lowered compared to the norm even more than growth), photosensitivity, deafness, and various visual impairments (optic atrophy, cataracts, degeneration of the corneal epithelium, retinal injuries). The average life expectancy of patients with Cockayne syndrome is 12 years. In the cells of patients, the process of nucleotide excision repair (NER), its branch coupled with transcription (transcription coupled repair: TCR) (TC-NER), is disrupted. When studying the panel of aging markers (SA-β-gal, γ-H2AX, 53BP1, HP1-γ, SIRT1, SIRT6, 3meH3K9, 3meH3K27), as well as structural damage to nuclear lamina and telomere shortening, it was shown that the cells of patients with Cockayne syndrome have pronounced signs of accelerated aging in all studied markers. This allows us to consider Cockayne syndrome to be a true progeria and use cell lines obtained from patients as model objects for studying the processes of aging and testing geroprotectors.