Tumor Suppressors TSC1 and TSC2 Differentially Modulate Actin Cytoskeleton and Motility of Mouse Embryonic Fibroblasts

TSC1 and TSC2 mutations cause neoplasms in rare disease pulmonary LAM and neuronal pathfinding in hamartoma syndrome TSC. The specific roles of TSC1 and TSC2 in actin remodeling and the modulation of cell motility, however, are not well understood. Previously, we demonstrated that TSC1 and TSC2 regulate the activity of small GTPases RhoA and Rac1, stress fiber formation and cell adhesion in a reciprocal manner. Here, we show that Tsc1^−/− MEFs have decreased migration compared to littermate-derived Tsc1^+/+ MEFs. Migration of Tsc1^−/− MEFs with re-expressed TSC1 was comparable to Tsc1^+/+ MEF migration. In contrast, Tsc2^−/− MEFs showed an increased migration compared to Tsc2^+/+ MEFs that were abrogated by TSC2 re-expression. Depletion of TSC1 and TSC2 using specific siRNAs in wild type MEFs and NIH 3T3 fibroblasts also showed that TSC1 loss attenuates cell migration while TSC2 loss promotes cell migration. Morphological and immunochemical analysis demonstrated that Tsc1^−/− MEFs have a thin protracted shape with a few stress fibers; in contrast, Tsc2^−/− MEFs showed a rounded morphology and abundant stress fibers. Expression of TSC1 in either Tsc1^−/− or Tsc2^−/− MEFs promoted stress fiber formation, while TSC2 re-expression induced stress fiber disassembly and the formation of cortical actin. To assess the mechanism(s) by which TSC2 loss promotes actin re-arrangement and cell migration, we explored the role of known downstream effectors of TSC2, mTORC1 and mTORC2. Increased migration of Tsc2^−/− MEFs is inhibited by siRNA mTOR and siRNA Rictor, but not siRNA Raptor. siRNA mTOR or siRNA Rictor promoted stress fiber disassembly in TSC2-null cells, while siRNA Raptor had little effect. Overexpression of kinase-dead mTOR induced actin stress fiber disassembly and suppressed TSC2-deficient cell migration. Our data demonstrate that TSC1 and TSC2 differentially regulate actin stress fiber formation and cell migration, and that only TSC2 loss promotes mTOR- and mTORC2-dependent pro-migratory cell phenotype.     

Association of the Ile50Val Polymorphism of the Interleukin-4 Receptor Gene IL4RA with Chronic Viral Hepatitis

The Ile50Val polymorphism of the IL4RA gene was tested for association with chronic viral hepatitis and the character of its progression (the stage of hepatic fibrosis). In total, 61 patients were examined. The control group was a random sample of Tomsk residents (N = 128). Genotyping was based on RFLP analysis. The allele and genotype frequencies of the Ile50Val polymorphism did not significantly differ between the patients and the controls. However, a significant difference in genotype frequency distribution was observed for the patients with different stages of hepatic fibrosis. The frequency of heterozygotes Ile/Val in patients without signs of fibrosis was lower than in the control group (7.1% vs. 51.6%, P = 0.002), while the frequency of the homozygous genotypes was higher. In addition, this subgroup significantly differed in genotype frequency distribution from subgroups of patients with early or severe fibrosis (P = 0.035 and P = 0.004, respectively).__________Translated from Molekulyarnaya Biologiya, Vol. 39, No. 3, 2005, pp. 379–384.Original Russian Text Copyright © 2005 by Goncharova, Friedin, Dunaeva, E.V. Beloborodova, E.I. Beloborodova, Puzyrev.     

Permissible level of laser radiation of wavelength 10.6 microns

In a four-month experiment with 102 male rabbits and 42 HRS/U mice and 30 days after termination thereof, study was made of local and general response of an organism to the effect of laser radiation (10.6 microns wave length and energy exposition 1/7 of the threshold). The radiation tolerance level was estimated.     

Clinico-roentgenologic diagnosis of disseminated and diffuse lung diseases

The results of clinical and x-ray investigations of 398 patients with disseminated pulmonary lesions were analyzed. Two groups were identified: patients with interstitial type of lesions (101) and patients with focal type of lesions (297). Proceeding from roentgeno-morphological correlations, the authors presented specified roentgeno-semiotics of 10 nosological entities with the syndrome of pulmonary dissemination. The possibilities of optimization of differential diagnosis of disseminated pulmonary lesions were shown basing on combined (clinical, functional and roentgenological) investigation.     

Presenilin-1 Delta E9 Mutant Induces STIM1-Driven Store-Operated Calcium Channel Hyperactivation in Hippocampal Neurons

Presenilins regulate calcium homeostasis in the endoplasmic reticulum, and dysregulation of intracellular calcium has been implicated in the pathogenesis of Alzheimer disease. Elevated presenilin-1 (PS1) holoprotein levels have been detected in postmortem brains of patients carrying familial Alzheimer disease (FAD) PS1 mutations. This study examines the effect of the FAD presenilin mutant that lacks the ninth exon (PS1 ?E9) and does not undergo endoproteolysis on store-operated calcium (SOC) entry. Significant enhancement of SOC channel activation was detected by electrophysiological measurements in hippocampal neurons with PS1 ?E9 mutant expression. Here, we show that (i) the hyperactivation of SOC channels is mediated by the STIM1 sensor and can be attenuated by STIM1 knockdown or 2-aminoethoxydiphenyl borate application, (ii) the STIM2 is not involved in pathological changes of SOC entry, (iii) the pathological SOC entry demonstrates properties of both TRPC and Orai subunit composition, and (iiii) transgenic Drosophila flies with PS1 ?E9 expression in the cholinergic neuron system show short-term memory loss, which can be abolished by 2-aminoethoxydiphenyl borate feeding.     

Ethnic and Geographical Aspects of the Prevalence of the Polymorphic Variants of Genes Associated with Tuberculosis

Specificity of the structure of gene pools of different ethno-territorial groups of the human population can underlie the epidemiological features of the spread of tuberculosis (TB) and the structure of the genetic component of the susceptibility to the disease. The variability of 62 genetic variants potentially associated with the risk of the development of TB in the Russian population of the city of Tomsk has been studied and the differentiation of various ethno-territorial groups of the world by these markers has been assessed. The studied sample comprised 445 Russian residents of the city of Tomsk without bronchopulmonary pathology. For comparison, the data on the variability of the genetic markers of interest in 26 populations from the 1000 Genomes Project was involved. In the Tomsk population, only the ancestral allele was found for seven of the 58 SNPs studied; the allele frequencies for 36 markers were within the limits of the values seen in other European populations; for 12 SNPs, the observed frequencies were closer to populations with a significant Mongoloid component. By the total of the SNPs, the Tomsk population, despite the geographical distance from the rest of the European populations, did not differ from them (in genetic distances and G_st statistics), although it had some features of the gene pool. Intergroup differentiation of the world populations by these SNPs reflects mainly interracial differences. The greatest differences in the genetic structure between the studied populations were seen for the markers localized in intergenic regions. Statistically significant differences were found when comparing the levels of the average expected heterozygosity between groups of “L4 carrier populations” of mycobacteria and “non-L4” populations, which indicates the impact of the prevalence of different pathogenic lineages of M. tuberculosis on the formation of population specificity of the allelic frequencies.     

Genes for fibrogenesis in the determination of susceptibility to myocardial infarction

A group of patients with ischemic heart disease and myocardial infarction (N = 156) and a reference population sample (N = 300) were genotyped for 58 single nucleotide polymorphisms (SNPs) in the genes involved in extracellular matrix function and collagen metabolism or associated with cardiovascular diseases and atherosclerotic plaque stability. Genotyping was performed by mass-spectrometry with two multiplex sets of 27 and 31 SNPs. The study revealed different genetic composition of predisposition to cardiovascular disease continuum (CVDC) syntropy (patients with concomitant conditions: hypercholesterolemia, hypertension, and type-II diabetes mellitus, N = 96) and to isolated myocardial infarction (without these conditions, N = 60). Only the KIAA1462 gene (rs3739998) showed associations with both CVDC syntropy (OR = 1.71; 95% CI 1.19–2.45; р = 0.003) and isolated infarction (OR = 1.58; 95% CI 1.05–2.40; р = 0.028). Isolated myocardial infarction was also associated with LIG1 (rs20579) (OR = 2.08; 95% CI 1.06–4.17; р = 0.028) and ADAMDEC1 (rs3765124) (OR = 1.63; 95% CI 1.07–2.50; р = 0.020). CVDC syntropy was associated with CDKN2BAS1 (rs1333049) (OR = 1.48; 95% CI 1.03–2.12; р = 0.029) and APOA2 (rs5082) (OR = 1.47; 95% CI 1.02–2.11; р = 0.035). So, genes involved in fibrogenesis contribute to predisposition to the myocardial infarction as well. Isolated myocardial infarction and CVDC syntropy can be considered as pathogenetically different cardiovascular conditions, with different genes that contribute to the susceptibility.     

Gene amplification in murine leukemia cells with multiple drug resistance acquired in vivo

The P388rm and P388rx cell lines resistant to antracycline antibiotics were obtained as a result of chemotherapy of mice bearing P388 leukemia, by means of increasing dosages of rubomycin and ruboxyl, respectively. These cell lines possessed cross-resistance to vinblastine, vincristine, colchicine, actinomycin D and some other drugs. Multidrug resistance (MDR) of P388rm and P388rx is due to decreased uptake of different cytotoxic compounds by the cells. Development of resistance to rubomycin and ruboxyl was accompanied by the appearance of additional chromosomal structures--long homogeneously staining regions (HSRs), double minute chromosomes and others usually containing amplified DNA sequences. Southern blot-hybridization with cloned DNA fragments amplified in Djungarian and Chinese hamster cell lines having MDR has revealed in P388rm and P388rx cells approximately 50-fold amplification of mdr and pC52 genes. Thus, in mouse leukemia cells which acquired MDR in vivo, as a result of chemotherapy, amplification is observed of the same genes that undergo amplification during selection of cell cultures for MDR in vitro.     

Axospinal synapses in the forebrain cortex of aquatic and terrestrial turtles

An electron microscopical investigation of synaptic organization of the superficial plexiform layer of three forebrain cortical zones (hippocampal, dorsal and piriform) in two aquatic and two land Chelonia species has been performed. As demonstrate the data obtained and those from the literature, the main elements of the axo-spinal complexes (spines--synapses--neural terminals) possess both stability properties, contributing to structural firmness of the contacts and their reliability during activities, and plastisity ensuring the maintenance of dynamic equilibrium and a possibility for adequate rearrangements. Under normal conditions, the functional shifts in ultrastructure of the synaptic apparatuses are, possibly, so negligible that they cannot mask certain specific fractures of the synaptic organization of the neural centers. When comparing structures of the axo-spinal complexes in functionally dissimilar cortical zones, more constant, common for all species of Chelonia studied signs are definitely revealed. They characterize a certain level of the neural processes integration. There are signs more variable, evidently, ensuring adaptive rearrangements within limits of the given level of the interneuronal connections organization which can be considered as ecological and species-specific peculiarities.     

Comparative biological characteristics of the L-form of Streptococcus group A and B

The comparative study of the biological and serological properties of the L-forms of streptococci, groups A and B, has been made. Their morphological similarity on the level of light microscopy has been demonstrated. The use of ring precipitation, gel diffusion, passive hemagglutination, aggregate hemagglutination, as well as the immunoferritin technique, has made it possible to establish the presence of specific antigens in the L-forms of streptococci, groups A and B. Serological cross reactions are negligible. The future development of a diagnosticum for the specific indication of these antigens is proposed. The fact of the presence of specific antigens in the L-forms of streptococci in comparison with the initial streptococcal strains has been confirmed.