About 13% of all variants causing cystic fibrosis are splice variants of the CFTR gene; at the moment, such variants are not well studied.The aim was to investigate the effect of the splicing variant 2789+5G>A on the phenotypic manifestations of cystic fibrosis and the effectiveness of targeted therapy in an intestinal organoids model in the patients with genotypes 2789+5G>A/L732X and 2789+5G>A/CFTRdele2,3.Methods. The medical history data, intestinal current measurement (ICM), and forskolin-induced swelling assay in the intestinal organoids were used.Results. The clinical features of the course of CF in 2 patients, carriers of the 2789+5G>A variant in a heterozygous state with genetic variants of the CFTR gene of classes I and VII, are presented. Clinical picture: the disease is of moderate severity; the pancreas is sufficient. The ICM method demonstrated the preservation of the chloride channel function. Assays on the cultured organoids obtained from the intestinal tissue showed moderate residual functional activity of the chloride channels. In addition, the 2789+5G>A variant is sensitive to all tested CFTR modulators.Conclusions. The splicing variant 2789+5G>A is characterized by moderate residual functional activity of the CFTR channel and is sensitive to all targeted treatments. However, the most effective CFTR modulator for this genetic variant is tezacaftor.

Изучение редких вариантов в гене CFTR является актуальным в эпоху таргетной терапии CFTR-модуляторами. В данном исследовании изучена клиническая картина муковисцидоза, а также функция CFTR-канала у гомозиготного носителя редкого патогенного варианта c.1329_1350del (p.Asp443GlufsX19), относящегося к I классу нарушений в гене CFTR. Получена полная корреляция результатов функциональных тестов с фенотипической картиной муковисцидоза и потовым тестом. Метод определения разности кишечных потенциалов продемонстрировал отсутствие функциональной активности хлорного CFTR канала в ректальном биоптате; при стимулировании форсколином органоиды пациента не ответили набуханием, что свидетельствует о полном нарушении образования функционального белка CFTR. Воздействие на кишечные органоиды всеми зарегистрированными для терапии таргетными препаратами не привело к их набуханию, в отличие от контрольной культуры, гомозиготной по F508del, таким образом, хлорный канал пациента с генотипом p.Asp443GlufsX19/p.Asp443GlufsX19 оказался нечувствителен ни к одному CFTR-модулятору. The study of rare variants in the CFTR gene is relevant in the era of targeted therapy with CFTR modulators. In this study, we studied the clinical picture of cystic fibrosis, as well as the function of the CFTR channel in a homozygous carrier of a rare pathogenic variant c.1329_1350del (p.Asp443GlufsX19), belonging to class I disorders in the CFTR gene. A complete correlation of the results of functional tests with the phenotypic pattern of CF and data of a sweat test was obtained. The method for determining the difference in intestinal potentials demonstrated the absence of functional activity of the chloride CFTR channel in the rectal biopsy, and when stimulated with forskolin, the patient’s organoids did not swell, which indicates a complete violation of the functional CFTR protein production. Exposure to intestinal organoids by all registered for therapy targeted drugs did not lead to their swelling, unlike the control culture, homozygous for F508del. The chloride channel of a patient with genotype p.Asp443GlufsX19/p.Asp443GlufsX19 turned out to be insensitive to any CFTR modulator.

The presence of pathogenic variants in the CFTR gene causes cystic fibrosis (CF) through various molecular mechanisms that affect the formation and functional activity of the CFTR chloride channel. An important factor affecting the phenotypic manifestations of CF and the effectiveness of targeted therapy is the presence of complex alleles with > 2 consecutive mutations per 1 allele, or in the cis position. The influence of complex alleles on the manifestations of CF has not been sufficiently studied globally due to the small number of studies. The aim of the study was to investigate the influence of the complex allele [S466X; R1070Q] on the phenotypic manifestations of CF and the effectiveness of targeted therapy in a model of intestinal organoids from a patient with [S466X; R1070Q]/CFTRdele2,3 genotype. Methods. We used medical history data, intestinal current measurement, intestinal organoid method, and forskolin test. Results. The progressive nature of the disease with a clear degradation of lung function was established. The ICM method showed absent chloride channel function. The tests on the culture of organoids obtained from the intestinal tissue indicated a complete loss of the chloride channel function. In addition, the complex allele [S466X; R1070Q] was insensitive to all targeted drugs tested. Conclusion. The complex allele [S466X; R1070Q] causes a complete loss of the functional CFTR protein and is not sensitive to any of the approved targeted drugs.

Clinical manifestations of cystic fibrosis depend on the patient’s genotype since there are more than 2,000 variants of the CFTR gene. Main complications of the disease are expressed in a reduction or loss of pancreatic function and bacterial lung infection, leading to respiratory failure. The E92K (p.(Glu92Lys) and 4428insGA (p.(Ser1435Glyfs*14) mutations in the CFTR gene are accompanied by a high frequency of preserved pancreatic function. In a 3-year-old patient with recurrent pancreatitis and E92K/4428insGA genotype, the functional activity of the CFTR channel was studied using the intestinal current measurement method on rectal biopsy specimens and the forskolin-induced swelling assay in intestinal organoids. The personalized assessment of the action of CFTR modulators was also performed on organoid cultures obtained from the patient’s intestinal biopsies. In a 3-year-old child with cystic fibrosis and recurrent pancreatitis with frequent exacerbations, a high preservation of residual CFTR channel function was revealed. All the investigated targeted drugs were effective in increasing the functional activity of the CFTR chloride channel. Key words: cystic fibrosis, CFTR gene, targeted therapy, pancreatitis, intestinal organoids, intestinal current measurement, E92K, 4428insGA

The CFTR gene contains 27 exons and is located at position 31.1 of the long arm of chromosome 7 (7q31.1). More than 2000 variants of the CFTR gene have been described so far. The R334W variant is associated with the mild disease course. Objective. To perform comprehensive assessment of the health status, functional CFTR activity, and efficacy of CFTR modulators in twins with the F508del/R334W genotype. Materials and methods. Data from medical records, intestinal current measurement (ICM), intestinal organoid culture. Results. We examined two twins with moderate cystic fibrosis who had similar clinical manifestations, including rhinosinusitis with nasal polyps and respiratory infections caused by gram-negative bacteria. Both patients also had polyvalent allergy. One child presented with a decrease of pancreatic elastase 1 in stool from 500 μg/g to 125 500 μg/g, which required administration of pancreatin and dosage increase later. Both children had reduced chloride channel function as demonstrated by ICM. The administration of a corrector (VX-809) and a potentiator (VX-770) effectively restored the channel function; their simultaneous use ensured an additive effect. The quantitative results obtained in both cultures of intestinal organoids were very similar. Key words: cystic fibrosis, CFTR gene, pathogenic variant R334W, intestinal current measurement, intestinal organoids, forskolin-induced swelling assay, correctors, potentiators, targeted therapy, ivacaftor, lumacaftor

Rationale: Cystic fibrosis is a common monogenic disease related to pathogenic nucleotide sequence variants in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) (ABCC7) gene. The CFTR gene consists of 27 exons and is located in the 31.1 region on the long arm of chromosome 7 (7q31.1). The use of the sequencing method has led to the accumulation of new information about the diversity of genetic variants in cystic fibrosis. This information is important considering approaches to the development of targeted therapy for the disease, based on an individual genotype. No targeted therapy has been developed for the N1303K class II genetic variant. The function of the chloride channel in this mutation has not been compared with that in class II mutations like F508del.Materials and methods: We have analyzed medical files of a patient with cystic fibrosis and F508del/N1303K CFTR genotypes, including the results of rectal biopsy samples. The assessments included measurement of the intestinal potential difference and forskolin-induced swelling assay (FIS) in rectal organoids, with the results being analyzed in relation to the clinical data.Results: The results of intestinal current measurements (ICM) confirm that the N1303K genetic variant is “severe” and leads to the loss of the working CFTR protein, which is consistent with the clinical manifestations. The mean short circuit currency density (ΔISC) in response to amiloride (sodium channel stimulation) was -39 ± 1.22 µA/cm2, to forskolin (chloride channel stimulation) 3.83 ± 1.43 µA/cm2, to carbachol 6 ± 2.47 µA/cm2, and to histamine 8.5 ± 3.02 µA/cm2.FIS results indicate that the VX-770 potentiator and the VX-809 corrector have a weak effect on the stimulation of organoids by forskolin in the genetic variant N1303K: organoid swelling was non-significant (about 20% from their baseline size).Conclusion: The use of the ICM method and FIS assay in human intestinal organoids makes it possible to quantify the work of the CFTR protein and determine the in vitro effectiveness of targeted therapy in patients with cystic fibrosis. CFTR modulators are ineffective in patients with N1303K mutation in the compound-heterozygous condition with F508del, despite both pathogenic variants belong to class II.

Cystic fibrosis (CF) is a systemic hereditary disease caused by a mutation of the CFTR gene and characterized by damage to the glands of external secretion and severe dysfunctions of the respiratory system. The “severe” genotypes are associated with more pronounced and early clinical manifestations. The “mild” genotypes are associated with a delayed onset of clinical manifestations.Methods. An analysis of the medical history of patients with asymptomatic CF from the Russian CF centers was carried out. Rectal biopsy specimens were used for intestinal current measurement (ICM) and forskolin-induced swelling assay in intestinal organoids. DNA for sequencing was isolated from the venous blood leukocytes.Results. 2 CF patients with genotypes F508del/c.1584+18672A>G (patient 1, 12 years old) and F508del/G509D-E217G (patient 2, 3 years old) were examined. The diagnosis was based on neonatal screening. The ICM assay showed a reduced function of the CFTR channel: ΔISC for forskolin was 12.33 ± 2.35 μA/cm2 in patient 1 and 25 ± 3.37 μA/cm2 in patient 2. The negative response to carbachol and histamine reflects the entry of potassium ions into the cells, which is typical for CF. The assay in intestinal organoids showed that the amount of functional protein on the apical membrane of the intestinal epithelium increases both under the action of the potentiator and the corrector in both patients. The greatest effect is observed when the VX-770 and VX-809 are used together.Conclusion. The ICM functional assay and the forskolin-induced swelling assay in intestinal organoids are sensitive enough to determine the residual functional activity of the CFTR channel and clarify the diagnosis in difficult cases. The studied genetic variants c.1584+18672A>G and G509D-E217G belong to class IV – VI mutations. The clinical picture corresponds to the manifestations of “mild” mutations. The studied patients still attend the Russian cystic fibrosis centers.

Intestinal current measurement (ICM) and forskolin-induced swelling (FIS) assay in human intestinal organoids from rectal biopsies of cystic fibrosis (CF) patients are the new functional tests for assessment of CFTR channel activity that are widely used in the leading laboratories worldwide for scientific and clinical studies.The aim of the study was to assess the use of the new functional tests in adult CF patients with identified N1303K and R334W CFTR gene variants.Methods. Rectal suction biopsies were obtained from the two CF patients aged 36 and 27 years with N1303K/3821delT and R334W/F508del CFTR mutations, respectively. Results of the ICM and FIS assay in intestinal organoids were compared to the clinical data.Results. ICM has demonstrated that R334W is a ‘mild’ genetic variant with high residual CFTR channel activity. At the same time, N1303K is a ‘severe’ genetic variant and leads to a severe loss of CFTR channel function. These findings correlate with the clinical data. CFTR modulators compensate for the reduced activity of the R334W CFTR variant, as shown by the FIS assay. But there was a limited response of the forskolin-stimulated organoids to VX-770 potentiator and VX-809 corrector in the cells with N1303K genetic variant.Conclusion. ICM and FIS assay in human intestinal organoids are reliable methods for quantification of CFTR channel activity. They can also predict the efficacy of the targeted therapy in CF patients in vivo.

We performed comparative analysis of paracrine activity of neuronal and glial progenitors derived from induced pluripotent stem cells under conditions of hypoxia modeled by addition of cobalt dichloride. Neuronal and glial progenitors produced neuroprotective and neurotrophic effects on SHSY-5Y neuroblastoma cells in co-culture during the post-hypoxic recovery and reduced the number of apoptotic and necrotic cells. Moreover, they produced a neurotrophic effect and promote the formation and growth of neurites in neuroblastoma cells. The paracrine effect of glial progenitors was more pronounced, which can be explained by more intensive expression and secretion of neurotrophic factors in these cells.

ОПЫТ ПРИМЕНЕНИЯ МЕТОДОВ ОЦЕНКИ ФУНКЦИОНАЛЬНОСТИ АНИОННОГО КАНАЛА CFTR У ПАЦИЕНТОВ С УСТАНОВЛЕННЫМ И ПРЕДПОЛАГАЕМЫМ ДИАГНОЗОМ МУКОВИСЦИДОЗАе. И

В статье впервые представляется клинико-генетическая характеристика мутации c.1083G>A (p.Trp361*) в гене CFTR. Патогенный генетический вариант c.1083G>A (p.Trp361*) гена CFTR относится к нонсенс-мутациям (I класс) и впервые был внесён в базу данных CFTR1 (http://www.genet.sickkids.on.ca) в середине 2019 г. без описания клинической картины муковисцидоза. Методы. Проведен анализ амбулаторных карт и историй болезни двух пациентов из неродственных семей с редким генетическим вариантом c.1083G>A (p.Trp361*). Для определения разности кишечных потенциалов (ОРКП) и проведения форсколинового теста на кишечных органоидах использовали биопсийный материал слизистой прямой кишки пациентов. ДНК для секвенирования выделяли из лейкоцитов венозной крови пациентов. Результаты. Анализ клинических проявлений заболевания у детей 6 и 9 лет показал наличие хронической панкреатической недостаточности, более выраженной у одного ребенка с синдромом дистальной интестинальной обструкции кишечника в анамнезе. Клиническая картина второго пациента характеризовалась развитием в раннем возрасте транзиторной гипербилирубинемии, синдрома псевдо-Барттера, а в дальнейшем - повторными эпизодами бронхиальной обструкции и развитием полипозного риносинусита. ОРКП и форсколиновый тест на кишечных органоидах показали, что генетический вариант c.1083G>A (p.Trp361*) относится к вариантам гена CFTR с отсутствием функции хлорного канала. Выводы. Впервые представлены описание клинической картины муковисцидоза у двух пациентов из неродственных семей с патогенным вариантом c.1083G>A (p.Trp361*) в компаунде с вариантом c.1521_1523delCTT (p.Phe508del) (ранее называемом F508del) и результаты оценки функции белка CFTR методом ОРКП и форсколиновым тестом на кишечных органоидах. In this article we continue to describe the pathogenic variants of the CFTR gene identified among Russian cystic fibrosis (CF) patients. For the first time the clinical and genetic characteristics of the mutation c.1083G> A (p.Trp361 *) are presented. The pathogenic genetic variant c.1083G> A (p.Trp361 *) of the CFTR gene belongs to the nonsense mutations (class I) and was listed for the first time in the CFTR1 database (http://www.genet.sickkids.on.ca) by Professor Milan Macek et al. in mid-2019 without any description of clinical manifestations of cystic fibrosis. Methods. The data of the National Register of Patients with Cystic Fibrosis of the Russian Federation 2017 were analyzed. Outpatient records and case histories of two patients from unrelated families carrying a rare genetic variant c.1083G> A (p.Trp361 *) were analyzed. To determine the Intestinal current measurement (ICM) and Forskolin-induced swelling (FIS) in intestinal organoids, rectal biopsy material of CF patients was used. DNA for sequencing was isolated from leukocytes of venous blood of the patients. Results. Variant c.1083G> A (p.Trp361 *) was found in two patients from unrelated families from different regions of the Russian Federation, according to the Register of Cystic Fibrosis Patients in the Russian Federation 2017. Analysis of clinical manifestations of the disease in children 6 and 9 years old showed the presence of chronic pancreatic insufficiency, more expressed in one child with a history of distal intestinal obstruction syndrome. The clinical manifestation of the second patient was characterized by the development of transient hyperbilirubinemia, Pseudo-Bartter’s syndrome at an early age, and subsequently repeated episodes of bronchial obstruction and the development of polypoid rhinosinusitis. The ICM method and the FIS in intestinal organoids showed that the genetic variant c.1083G> A (p.Trp361 *) refers to the variants of the CFTR gene with the absence of chlorine channel function. Conclusion. The clinical picture of cystic fibrosis in two patients from unrelated families with the pathogenic variant c.1083G> A (p.Trp361 *) in the compound with variant c.1521_1523delCTT (p.Phe508del) (variant legacy name F508del) and results of the evaluation of the CFTR protein functions, obtained by the method of ICM and using the FIS assay in intestinal organoids, are presented for the first time. Patients continue to be under the control in Russian CF centers.

One of the main causes of cell death in neurodegenerative diseases is excitotoxicity. Today the potential directions of treatment neurodegenerative diseases are including cell therapy, the purpose of which is to replace lost nerve tissue with donor cells. Transplanted cells along with replaced lost tissues have a paracrine effect, which requires careful study. The aim of this work was to study the effect of conditioned media, obtaining from neuronal and glial progenitor cells, on a primary culture of cerebellar neurons in a model of glutamate excitotoxicity. The cell viability, expression of marker genes for apoptosis and neuritogenesis, and the number of necrotic and apoptotic cells were determined in the culture of cerebellar neurons. The composition of the studied conditioned media was analyzed for the content of neurotrophins. A comparative analysis was revealed differences in the secretion of neurotrophins between the obtained cultures: the amount of brain-derived neurotrophic factor, nerve growth factor, ciliary neurotrophic factor and glial neurotrophic factor was higher in the secretion of glial progenitors. It was shown that the addition of conditioned media from neuronal cells does not significantly affect the viability of cerebellar neurons, whereas preincubation with media from glial progenitors has a neuroprotective effect by increasing the viability of cerebellar neurons, and during long-term cultivation promotes the growth of neurites by increasing the expression level of MAP2 and GAP43 genes.