[Change of transcription level of photoreceptor-specific CRX gene in the peripheral blood of the participants of an arctic world oceanic international flight]. / Izmenenie urovnya transkriptsii fotoretseptor-spetsifichnogo gena CRX u uchastnikov arkticheskogo krugosvetnogo pereleta.

The CRX gene encoding the cone-rod homeobox protein is a specific photoreceptor transcription factor crucial for retinal function. Persons temporarily residing in the Arctic zone during the polar summer may suffer from disturbances associated with extremely high ambient illumination. These environmental changes are mediated by retinal photoreceptors; therefore, it is important to study the expression of retinal genes in order to assess individual capacities of sensory adaptation to polar day conditions. PURPOSE: To reveal the dynamics of CRX expression level in humans after a prolonged temporary exposure to polar day conditions. MATERIAL AND METHODS: The study included 6 pilots (males from 39 to 69 y.o.) who participated in the Arctic World Oceanic International Flight Sever Vash (West to East, from 62°N 74°E to 72°N 114°E). Samples of peripheral blood for RNA isolation were collected at the start and at the end of the flight. The level of mRNA in the samples was evaluated based on the data of quantitative real-time PCR of the CRX gene, as well as the b2M and TBP housekeeping genes (reference). RESULTS: Expression of the CRX gene in the studied group (p<0.01) was revealed; the total average level of mRNA was about 3 times higher prior to, and approximately 7 times higher after normalization to the b2M gene. Five pilots had increased expression of the CRX gene within the range of -1.53 to -3.07 (Z-score of <0 before the flight and >0 after the flight). In one pilot, the level of CRX expression was higher at the start, but it reduced by the end of the circumnavigation flight. CONCLUSIONS: The results confirm the hypothesis that the CRX gene is expressed after a prolonged temporary exposure to polar day conditions. It was also revealed that during rapid adaptation, equal changes in the illumination of retinal photoreceptors lead to different individual dynamics of CRX expression.

DNA methylation across the genome in aged human skeletal muscle tissue and muscle-derived cells: the role of HOX genes and physical activity.

Skeletal muscle tissue demonstrates global hypermethylation with age. However, methylome changes across the time-course of differentiation in aged human muscle derived cells, and larger coverage arrays in aged muscle tissue have not been undertaken. Using 850K DNA methylation arrays we compared the methylomes of young (27 ± 4.4 years) and aged (83 ± 4 years) human skeletal muscle and that of young/aged heterogenous muscle-derived human primary cells (HDMCs) over several time points of differentiation (0, 72 h, 7, 10 days). Aged muscle tissue was hypermethylated compared with young tissue, enriched for; pathways-in-cancer (including; focal adhesion, MAPK signaling, PI3K-Akt-mTOR signaling, p53 signaling, Jak-STAT signaling, TGF-beta and notch signaling), rap1-signaling, axon-guidance and hippo-signalling. Aged cells also demonstrated a hypermethylated profile in pathways; axon-guidance, adherens-junction and calcium-signaling, particularly at later timepoints of myotube formation, corresponding with reduced morphological differentiation and reductions in MyoD/Myogenin gene expression compared with young cells. While young cells showed little alterations in DNA methylation during differentiation, aged cells demonstrated extensive and significantly altered DNA methylation, particularly at 7 days of differentiation and most notably in focal adhesion and PI3K-AKT signalling pathways. While the methylomes were vastly different between muscle tissue and HDMCs, we identified a small number of CpG sites showing a hypermethylated state with age, in both muscle tissue and cells on genes KIF15, DYRK2, FHL2, MRPS33, ABCA17P. Most notably, differential methylation analysis of chromosomal regions identified three locations containing enrichment of 6-8 CpGs in the HOX family of genes altered with age. With HOXD10, HOXD9, HOXD8, HOXA3, HOXC9, HOXB1, HOXB3, HOXC-AS2 and HOXC10 all hypermethylated in aged tissue. In aged cells the same HOX genes (and additionally HOXC-AS3) displayed the most variable methylation at 7 days of differentiation versus young cells, with HOXD8, HOXC9, HOXB1 and HOXC-AS3 hypermethylated and HOXC10 and HOXC-AS2 hypomethylated. We also determined that there was an inverse relationship between DNA methylation and gene expression for HOXB1, HOXA3 and HOXC-AS3. Finally, increased physical activity in young adults was associated with oppositely regulating HOXB1 and HOXA3 methylation compared with age. Overall, we demonstrate that a considerable number of HOX genes are differentially epigenetically regulated in aged human skeletal muscle and HDMCs and increased physical activity may help prevent age-related epigenetic changes in these HOX genes.

Data on somatic mutations obtained by whole exome sequencing of FFPE tissue samples from Russian patients with prostate cancer.

Prostate cancer (PCa) is the most frequently diagnosed among men malignant disease that remains poorly characterized at the molecular level. Advanced PCa is not curable, and the current treatment methods can only increase the life expectancy by several months. Identification of the genetic aberrations in tumor cells provides clues to understanding the mechanisms of PCa pathogenesis and the basis for developing new therapeutic approaches. Here we present data on somatic mutations, namely single nucleotide variations (SNVs), small insertions and deletions, detected in prostate tumor tissue obtained from Russian patients with PCa. Moreover, we provide a raw dataset on the whole exome and targeted DNA sequencing of tumor and non-tumor prostate tissue obtained from Russian patients with PCa and benign prostatic hyperplasia (BPH). This data is available at NCBI Sequence Read Archive under Accession No. PRJNA506922.

[Targeted gene sequencing panels: applicability for neoantigen profiling of colon and rectal adenocarcinoma]. / Vozmozhnosti primeneniia targetnykh panelei dlia opredeleniia neoantigennogo profilia obraztsov adenokartsinomy tolstoi i priamoi kishki.

Cancer immunotherapy represents a promising and rapidly developing approach for the treatment of oncological diseases. Among the methods of personalized adjuvant immunotherapy, neoantigenic peptide-based drugs have demonstrated substantial efficiency. These drugs are designed to target mutant proteins arising from somatic alterations in the genome of tumor cells and thus stimulate immune response against tumor tissues. The methods of individual screening for potentially immunogenic mutations are mostly based on next-generation exome sequencing of tumor samples, which is a complex and costly procedure for clinical application. Targeted gene sequencing panels limited to a certain set of genes represent a reasonable alternative to WES. Targeted sequencing is also more efficient when there is a low amount of the sample DNA available. We have estimated the potential efficiency of targeted oncological panels in terms of somatic neoantigen profiling in colorectal cancer (colon and rectal adenocarcinoma). The clinical practice of identification of frequent somatic variants does not provide enough data for designing an efficient personalized drug when applied to low and medium mutated cancers such as colorectal cancer. Our analysis of 11 commercially available panels containing different number of genes has shown that neither the larger size of a panel nor its initial customization for colorectal cancer provides a significantly better estimation of an individual somatic mutation profile. The optimal approach is to use the general-purpose medium-sized cancer panels (2300-11200 amplicons and/or 150-600 genes). These panels allow to detect a sufficient number of immunogenic epitopes (>3) per patient for over 30-50% of patients.

[GSTP1, APC and RASSF1 gene methylation in prostate cancer samples: comparative analysis of MS-HRM method and Infinium HumanMethylation450 BeadChip beadchiparray diagnostic value]. / Status metilirovaniia genov GSTP1, APC i RASSF1 v obraztsakh raka predstatel'noi zhelezy cheloveka: sravnitel'nyi analiz diagnosticheskoi informativnosti metodov MS-HRM i gibridizatsii na DNK-chipakh illumina Infinium HumanMethylation450 BeadChip.

There is a clear need in molecular markers for prostate cancer (PC) risk stratification. Alteration of DNA methylation is one of processes that occur during ÐÑ progression. Methylation-sensitive PCR with high resolution melting curve analysis (MS-HRM) can be used for gene methylation analysis in routine laboratory practice. This method requires very small amounts of DNA for analysis. Numerous results have been accumulated on DNA methylation in PC samples analyzed by the Infinium HumanMethylation450 BeadChip (HM450). However, the consistency of MS-HRM results with chip hybridization results has not been examined yet. The aim of this study was to assess the consistency of results of GSTP1, APC and RASSF1 gene methylation analysis in ÐÑ biopsy samples obtained by MS-HRM and chip hybridization. The methylation levels of each gene determined by MS-HRM were statistically different in the group of PC tissue samples and the samples without signs of tumor growth. Chip hybridization data analysis confirmed the results obtained with the MS-HRM. Differences in methylation levels between tumor tissue and histologically intact tissue of each sample determined by MS-HRM and chip hybridization, were consistent with each other. Thus, we showed that the assessment of GSTP1, APC and RASSF1 gene methylation analysis using MS-HRM is suitable for the design of laboratory assays that will differentiate the PC tissue from the tissue without signs of tumor growth.

[THE EVOLUTION OF MARKERS OF PROSTATE CANCER].

The implementation of biochemical laboratory tests in oncology practice increased exponentially during last decades and continues to be in progress nowadays. The application of modern molecular genetic technologies permits using diagnostic systems with greater diagnostic sensitivity and specificity. The new tests are actively implemented permitting to diagnose physical presence of tumor systemic manifestations of malignant neoplasm (cachexia, pyrexia), paraneoplastic syndromes and also to detect tumor markers. The oncomarker permits to differentiate malignant from benign tumor on the basis of quantitative differences in content of corresponding antigene-tumor marker in blood serum independently of localization of tumor nidus. The prostate cancer is a medical social problem of male population. On initial stages, this disease can take its course asymptomatically or with symptomatic conditioned by such concomitant and more prevalent pathologies as chronic prostatitis and prostate benign hyperplasia. The early diagnostic ofprostate cancer permits implementing timely radical treatment frequently contributing to total recovery of patients. The article presents detailed description of evolutionary conception of markers using in diagnostic, staging and prognostication of course of prostate cancer. The acid phosphatase was applied for the first time in early diagnostic of staging of prostate cancer in 1974. Nowadays, in century of "OMX"-technologies, in common clinical practice detection of RNA in urine of patient is used for staging diagnostic and prognostication of progression of process of tissue neotransformation.

[Current principles in the screening, diagnosis, and therapy of colorectal cancer].

The data available in the literature on the prevalence of colorectal cancer (CRC), its risk factors and genetic aspects are analyzed. Basic screening tests and their diagnostic value are described. The paper indicates the importance of methods (colonoscopy, occult blood feces analysis, fecal immunochemical test, determination of molecular genetic profile of fecal enterocytes) for the early primary diagnosis of colonic epithelial tumors and techniques (echography, computed tomography, magnetic resonance imaging, positron emission tomography) that are required to specify clinical TNM staging and enable one to choose an optimal treatment policy for CRC patients owing to the estimation of tumor volume and to the diagnosis of reginal and distant metastases. It also shows that new screening methods based on the detection of molecular markers for early (premorphological) tumor stages are promising. The role of primary CRC prevention aimed at molding and maintaining a healthy lifestyle in the population is demonstrated.

[Genome-wide analysis of DNA methylation in prostate cancer using the technology of Infinium HumanMethylation450 BeadChip (HM450)].

Using the technology of DNA chips Infinium HumanMethylation 450 BeadChip it was analyzed quantitative DNA methylation status in 12 paired samples of prostate adenocarcinoma, and morphologically altered tissues. Analysis of differentially methylated regions of the genome showed an association with abnormal status for 21610 and 3852 hypomethylated hyper-methylated CpG sites. Dominance in the cancer genome hypermethylated sites and their predominant localization in the regulatory regions of genes indicate their possible role in the implementation of mechanisms of gene suppression in the pathogenesis of prostate cancer (PCa). For 14 genes studied were characterized array maximum values hypermethylation in promoter region (> 50% CpG sites) in combination with a high level of methylation differences between treatment groups (> 40%). Role of hypermethylation in some of them: AOX1, KLF8, ZNF154, TMEM106A in the pathogenesis of prostate cancer has been showed previously. Hypermethylation of genes ACSS3, TAC1, TUBA4B, ZSCAN12 not previously been shown for prostate cancer, but is characterized by the association with other cancers. In turn, the differences in the levels of methylation in genes GPRASP1, NKX2-6, ARX, CYBA, EPSTI1, RHCG been documented as a result of a number of genome-research oncology, but has not been studied in detail. To assess the diagnostic potential of epigenetic markers of prostate cancer there was carried out unbiased selection of individual CpG sites most reliably discriminate against tumor samples from a group of no tumor samples. In selected diagnostic model based on logistic regression included 9 CpG sites. Validation of the model was carried out on an independent dataset of methylation of 40 paired samples from the prostate cancer project Atlas of Cancer Genome (TCGA) analyzed on the same version of the DNA chip. Summarized rates of diagnostic informativeness of a model (specificity 95%, sensitivity of 97%, the area under the curve of the diagnostic test (ROC) - 0,96), obtained after validation, allow us to consider these CpG Sites as potential markers for molecular diagnosis of prostate cancer.

[Molecular mechanisms of lung cancer development at its different stages in nuclear industry workers].

OBJECTIVE: to assess mutational events in exons 5, 7, and 8 of the p53 gene and to reveal mutant p53 protein in verified cases of morphologically altered (proliferative and precancerous changes, lung cancer) and histologically unaltered, lung tissues in workers exposed to occupational radiation. MATERIAL AND METHODS: The investigation used formalin-fixed paraffin-embedded unaltered and altered lung tissue blocks (FFPBs) obtained from the human radiobiological tissue repository. The shelf-life of FFPBs was 5-31 years. An immunohistochemical technique using mouse antibodies against p53 protein (<>, Denmark), stained with diaminobenzidine (DAB) chromogen, was employed to determine p53 protein. DNA was isolated from lung tissue FFPBs with QIAmp DNA FFPE Tissue Kit, (<>, USA). Polymerase chain reaction (PCR) was performed to amplify the p53 gene exons 5, 7, and 8 selected for examination, by applying the sequences of genes and primers, the specificity of which was checked using the online resource (http://www.ncbi.nlm.nih.gov/blast). PCR products were detected by temporal temperature gradient gel-electrophoresis and the Sanger sequencing method. The obtained DNA fragments were analyzed on a sequencer ABI Prism 3100 Genetic Analizer (<>, USA). Computer-aided DNA analysis was made using the BLAST program. A package of applied Statistica 6.0 programs was employed for statistical data processing. Results. Immunohistochemical analysis showed that mutant p53 protein was absent in the cells of unaltered lung tissue and the number of cells with mutant p53 protein increased in all the patients with proliferative and precancerous changes and lung cancer, suggesting p53 protein dysfunction. The total number of p53 gene mutations in exons 5, 7, and 8, if there were proliferative and precancerous lung tissue changes and lung cancer, were 25, 20, and 40%, respectively. All the found mutations were transversions (the substitution of purine for pyrimidine or, conversely), indicating the action of exogenous mutagens. CONCLUSION: The results of this investigation have confirmed other investigators' data showing that p53 gene mutations in lung cancer are observed in 40-70% of cases. The differences in the number of cases of altered lung tissue with mutations in the p53 gene (not more than 40%) and in those of p53 protein expression were found in 100%, suggesting the regulation of p53 gene function in the cell at multiple levels.

[Possibility of DNA isolation from archived autopsy tissues for molecular genetic studies].

Optimal conditions were defined for DNA isolation from formalin-fixed and paraffin-embedded (FFPE) archived autopsy lung tissue slices. The quality of DNA preparations isolated from the FFPE archived slices was assessed and their suitability for further molecular genetic analysis estimated. DNA isolated from the FFPE slices stored less and more than 10 years was suitable for molecular genetic studies in 100 and 66.7% of cases, respectively.

SOD2 gene polymorphism and muscle damage markers in elite athletes.

Exercise-induced oxidative stress is a state that primarily occurs in athletes involved in high-intensity sports when pro-oxidants overwhelm the antioxidant defense system to oxidize proteins, lipids, and nucleic acids. During exercise, oxidative stress is linked to muscle metabolism and muscle damage, because exercise increases free radical production. The T allele of the Ala16Val (rs4880 C/T) polymorphism in the mitochondrial superoxide dismutase 2 (SOD2) gene has been reported to reduce SOD2 efficiency against oxidative stress. In the present study we tested the hypothesis that the SOD2 TT genotype would be underrepresented in elite athletes involved in high-intensity sports and associated with increased values of muscle and liver damage biomarkers. The study involved 2664 Caucasian (2262 Russian and 402 Polish) athletes. SOD2 genotype and allele frequencies were compared to 917 controls. Muscle and liver damage markers [creatine kinase (CK), creatinine, alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP)] were examined in serum from 1444 Russian athletes. The frequency of the SOD2 TT genotype (18.6%) was significantly lower in power/strength athletes (n = 524) compared to controls (25.0%, p = 0.0076) or athletes involved in low-intensity sports (n = 180; 33.9%, p < 0.0001). Furthermore, the SOD2 T allele was significantly associated with increased activity of CK (females: p = 0.0144) and creatinine level (females: p = 0.0276; males: p = 0.0135) in athletes. Our data show that the SOD2 TT genotype might be unfavorable for high-intensity athletic events.

[Contemporary pharmacogenetic approaches to the treatment of age-related macular degeneration].

A study on the role of CFH, HTRA and IL-8 gene polymorphism in age-related macular degeneration (AMD) development has been conducted. At the first stage of the study genetic testing was done in 69 patients with exudative AMD and 370 random Moscow citizens without the disease. The goal of the second stage was to determine the influence of gene polymorphism on patient's response to endovitreal ranibizumab treatment. For that, visual acuity and foveal thickness were assessed before and after ranibizumab injections in 120 patients with wet AMD. All patients were genotyped for the genes of interest. The results showed that the presence of homozygous 402H polymorphism in CFH gene, as well as homozygous (-625)A mutation in HTRA1 gene, determines certain clinical presentations. Moreover, visual acuity below 0.1 and presence of 402H, (-625)A and (-251)A alleles in both copies of all three genes (CFH, HTRA and IL-8) are negative predictors of disease severity and antiangiogenic treatment response.

Associations of single nucleotide polymorphisms with malignant and borderline bone tumors.

Bone neoplasms - are a rare group of diseases, which ethiology and pathogenesis are not fully understood. We have studied 6 single nucleotide polymorphisms rs792/(GHI), rs7956547(IGFI), rs3761243(GNRH2), rs11737764(FGF2), rs6599400(FGFR3), and rs1690916(MDM2) associations with bone tumors. In our work we've detected significant associations with some single nucleotide polymorphisms: IGFl.rs7956547, GNRH2.rs3761243 and FGFR3.rs6599400 in patients with malignant and borderline bone tumors.

Association of FGFR3 and MDM2 gene nucleotide polymorphisms with bone tumors.

Association study of 6 candidate single-nucleotide polymorphisms (rs7921, rs7956547, rs3761243, rs11737764, rs6599400, rs1690916) was carried out in a group of patients with bone tumors of different histological structure (n=68) and control group of normal subjects (n=96). Significant associations of rs6599400 and rs1690916 polymorphisms with disease risk were detected (odds ratio 2.15 [1.06-4.24] and 0.39 [0.19-0.78], respectively). These polymorphisms were located in untranslated genome regions: polymorphism rs6599400 in the 5' region of fibroblast growth factor-3 receptor gene (FGFR3), rs1690916 in the 3' region of mouse MDM2 p53-binding protein homolog (MDM2). These data indicated a possible role of hereditary genetic factors in the formation of predisposition to bone sarcomas and confirmed previous findings according to which these genes should be regarded among the most probable factors involved in tumor development, including tumors of the bone and cartilage tissues.

[Influence of genetic mutations on clinical presentation of subretinal neovascularization. Report 1: The impact of CFH and IL-8 genes polymorphism].

Genetic analysis was performed in patients with subretinal neovascularization (CNV). The results showed significant association of CFH (compliment factor H) gene polymorphism with increase (rs1061170, rs514943 and rs380390) or decrease (rs529825, rs7524776, rs1831281, rs2274700, rs1576340, rs12144939, rs7540032) of CNV development risk. The incidence of IL-8 gene mutation was significantly (p = 0.008) higher in patients after chorioretinitis. Apparently -125 > A polymorphism in patients with chorioretinitis increases risk of CNV development, thus promoting raise of proangiogenic factors concentration in eyes with inflammatory background. The clinical presentation in patients with AMD and myopic disease associated with (-125) A mutation of promoter region of IL-8 gene was similar to that of patients with chorioretinitis. The features are the following: focal pattern, no drusen and RPE detachment, predominantly classic form of CNV (without occult pattern), formation of well-organized newly developed vessels.

[Hypermethylation of the CDH1, SEPT9, HLTF and ALX4 genes and their diagnostic significance in colorectal cancer].

Sequential treatment of bisulfate-converted DNA was used to study methylation of promoter areas of SEPT9, HLTF, ALX4 and CDH1 genes. Methylation profiles were evaluated by comparing bioptical findings on colorectal cancer (n=55) and morphologically intact areas of the large bowel (n=71). Significant differences between groups were established for SEPT9, HLTF and ALX4 genes (p < or = 10(-9)) in evaluating medium-rate methylation of CpG. Diagnostic sensitivity (Se) peaked for SEPT9 (78 +/- 7%); specificity--(86 +/- 4%) (Sp). On site CpG (position "+14"), similar findings were reported: Se=81 +/- 6%, Sp=77 +/- 5%. Therefore, CpG(14)SEPT9 may be used as a separate marker. As a result of the use of HLTF as marker on all 23 sites, Se was 67 +/- 6% and Sp--87 +/- 3%; ALX4 diagnostic sensitivity--59 +/- 6%. Specificity level was similar to those of the other genes (88 +/- 3%). Despite the role of CDH1 gene in colorectal cancer, the group-to-group differences in methylation rates were minimal. Such values of Se and Sp as 54 +/- 6% and 67 +/- 5%, respectively, could not support methylation of the CDH1 promoter area for diagnostic purposes. Therefore, combined evaluation of SEPT9, HLTF and ALX4 genes offered more advantage as far as diagnosis is concerned. Hypermethylation in two of the three genes was assumed as a criterion for diagnosis. Under such conditions, diagnostic sensitivity was 81 +/- 7% (Sp=93 +/- 3%). With such high values, the criterion has a potential of being instrumental in working out diagnostic tests for colorectal cancer.

[Problems and prospects of non-invasive screening for colorectal cancer].

High prevalence of colorectal cancer makes it a most serious socio-medical problem. Hence, the necessity of overall screening for prodromal changes and malignant neoplasms at the early stages of the disease. Despite a variety of efficacious instrumental diagnostic tools, the development of non-invasive screening techniques based on recent progress in understanding molecular mechanisms of carcinogenesis remains a highly topical issue. A pathogenetic model of colorectal cancer and pathophysiological basis of screening for colonic neoplasms are considered with the emphasis on the detection of tumour cells in faeces and their DNA carrying mutations in suppressor genes and oncogenes. Results of the studies with the use of one or several DNA oncomarkers are analysed in the context of their value for the diagnosis of colorectal neoplasms. High sensitivity and specificity of these methods make them very promising for application to the screening for colorectal cancer.

[Familial transthyretin amyloidosis].

A case of familial transthyretin amyloidosis with TTR Cys 114 gene polymorphism is described (first in Russia and third in the world). The clinical picture of the proband was dominated by symptoms of autonomous polyneuropathy (orthostatic hypotension, erectile dysfunction, diarrhea, tachycardia, foot dyshydrosis) and of somatic nerve lesions (dumbness, impaired surface and deep sensitivity in the limbs). The patient presented with vitreous body opacity, disturbed eye movements, lateralized sensory symptoms, and difficulty of speech (baryphonia). Electromyographic quantitative autonomous testing and measurement of evoked sympathetic skin potentials confirmed affection of peripheral nerves. Heart ultrasound revealed restrictive amyloid cardiopathy. Histological analysis showed amyloid deposition in the intestines and sural nerve. The proband, his daughter, brother (monozygous twin), and brother's daughter had mutant TTR Cys 114 gene. The brother also had amyloid deposits in the absence of clinical signs of the disease. Analysis of familial medical history demonstrated autosomal dominant inheritance of this mutation in 4 generations. Its possible origin and clinical features of the disease are discussed.

[Contribution of rennin-angiotensin-aldosterone system genes and NO synthase gene to the development of arterial hypertension].

Arterial hypertension (AH) is one of the most widespread cardiovascular disorders, 39.2% of men and 41.1% of women having elevated arterial pressure (AP). Hence, the necessity to elucidate possible causes of this abnormality. Heredity is considered to be a major factor determining AP in humans, and researchers all over the world are engaged in the search for AP markers. This paper is focused on genes controlling the renin-angiotensin-aldosterone system, viz. genes of angiotensin II, type 1 angiotensin II receptors, angiotensin-converting enzyme, and NO synthase. An overview of population studies with special reference to these genes indicates that molecular-genetic mechanisms of AH remain unclear. Joint efforts of researchers working in different centres are needed to address the problem.