Myofibrillogenesis in living cells microinjected with fluorescently labeled alpha-actinin

Fluorescently labeled alpha-actinin, isolated from chicken gizzards, breast muscle, or calf brains, was microinjected into cultured embryonic myotubes and cardiac myocytes where it was incorporated into the Z-bands of myofibrils. The localization in injected, living cells was confirmed by reacting permeabilized myotubes and cardiac myocytes with fluorescent alpha-actinin. Both living and permeabilized cells incorporated the alpha-actinin regardless of whether the alpha-actinin was isolated from nonmuscle, skeletal, or smooth muscle, or whether it was labeled with different fluorescent dyes. The living muscle cells could beat up to 5 d after injection. Rest-length sarcomeres in beating myotubes and cardiac myocytes were approximately 1.9-2.4 microns long, as measured by the separation of fluorescent bands of alpha-actinin. There were areas in nearly all beating cells, however, where narrow bands of alpha-actinin, spaced 0.3-1.5 micron apart, were arranged in linear arrays giving the appearance of minisarcomeres. In myotubes, alpha-actinin was found exclusively in these closely spaced arrays for the first 2-3 d in culture. When the myotubes became contraction-competent, at approximately day 4 to day 5 in culture, alpha-actinin was localized in Z-bands of fully formed sarcomeres, as well as in minisarcomeres. Video recordings of injected, spontaneously beating myotubes showed contracting myofibrils with 2.3 microns sarcomeres adjacent to noncontracting fibers with finely spaced periodicities of alpha-actinin. Time sequences of the same living myotube over a 24-h period revealed that the spacings between the minisarcomeres increased from 0.9-1.3 to 1.6-2.3 microns. Embryonic cardiac myocytes usually contained contractile networks of fully formed sarcomeres together with noncontractile minisarcomeres in peripheral areas of the cytoplasm. In some cells, individual myofibrils with 1.9-2.3 microns sarcomeres were connected in series with minisarcomeres. Double labeling of cardiac myocytes and myotubes with alpha-actinin and a monoclonal antibody directed against adult chicken skeletal myosin showed that all fibers that contained alpha-actinin also contained skeletal muscle myosin. This was true whether alpha-actinin was present in Z-bands of fully formed sarcomeres or present in the closely spaced beads of minisarcomeres. We propose that the closely spaced beads containing alpha-actinin are nascent Z-bands that grow apart and associate laterally with neighboring arrays containing alpha-actinin to form sarcomeres during myofibrillogenesis.

Dynamics of Z-band based proteins in developing skeletal muscle cells

During myofibril formation, Z-bodies, small complexes of alpha-actinin and associated proteins, grow in size, fuse and align to produce Z-bands. To determine if there were changes in protein dynamics during the assembly process, Fluorescence Recovery after Photobleaching was used to measure the exchange of Z-body and Z-band proteins with cytoplasmic pools in cultures of quail myotubes. Myotubes were transfected with plasmids encoding Yellow, Green, or Cyan Fluorescent Protein linked to the Z-band proteins: actin, alpha-actinin, cypher, FATZ, myotilin, and telethonin. Each Z-band protein showed a characteristic recovery rate and mobility. All except telethonin were localized in both Z-bodies and Z-bands. Proteins that were present both early in development in Z-bodies and later in Z-bands had faster exchange rates in Z-bodies. These results suggest that during myofibrillogenesis, molecular interactions develop between the Z-band proteins that decrease their mobility and increase the stability of the Z-bands. A truncated construct of alpha-actinin, which localized in Z-bands in myotubes and exhibited a very low rate of exchange, led to disruption of myofibrils, suggesting the importance of dynamic, intact alpha-actinin molecules for the formation and maintenance of Z-bands. Our experiments reveal the Z-band to be a much more dynamic structure than its appearance in electron micrographs of cross-striated muscle cells might suggest.

Analysis of myofibrillar structure and assembly using fluorescently labeled contractile proteins

To study how contractile proteins become organized into sarcomeric units in striated muscle, we have exposed glycerinated myofibrils to fluorescently labeled actin, alpha-actinin, and tropomyosin. In this in vitro system, alpha-actinin bound to the Z-bands and the binding could not be saturated by prior addition of excess unlabeled alpha-actinin. Conditions known to prevent self-association of alpha-actinin, however, blocked the binding of fluorescently labeled alpha-actinin to Z-bands. When tropomyosin was removed from the myofibrils, alpha-actinin then added to the thin filaments as well as the Z-bands. Actin bound in a doublet pattern to the regions of the myosin filaments where there were free cross-bridges i.e., in that part of the A-band free of interdigitating native thin filaments but not in the center of the A-band which lacks cross-bridges. In the presence of 0.1-0.2 mM ATP, no actin binding occurred. When unlabeled alpha-actinin was added first to myofibrils and then labeled actin was added fluorescence occurred not in a doublet pattern but along the entire length of the myofibril. Tropomyosin did not bind to myofibrils unless the existing tropomyosin was first removed, in which case it added to the thin filaments in the l-band. Tropomyosin did bind, however, to the exogenously added tropomyosin-free actin that localizes as a doublet in the A-band. These results indicate that the alpha-actinin present in Z-bands of myofibrils is fully complexed with actin, but can bind exogenous alpha-actinin and, if actin is added subsequently, the exogenous alpha-actinin in the Z-band will bind the newly formed fluorescent actin filaments. Myofibrillar actin filaments did not increase in length when G-actin was present under polymerizing conditions, nor did they bind any added tropomyosin. These observations are discussed in terms of the structure and in vivo assembly of myofibrils.

Analysis of cell division using fluorescently labeled actin and myosin in living PtK2 cells

Actin and the light chains of myosin were labeled with fluorescent dyes and injected into interphase PtK2 cells in order to study the changes in distribution of actin and myosin that occurred when the injected cells subsequently entered mitosis and divided. The first changes occurred when stress fibers in prophase cells began to disassemble. During this process, which began in the center of the cell, individual fibers shortened, and in a few fibers, adjacent bands of fluorescent myosin could be seen to move closer together. In most cells, stress fiber disassembly was complete by metaphase, resulting in a diffuse distribution of the fluorescent proteins throughout the cytoplasm with the greatest concentration present in the mitotic spindle. The first evidence of actin and myosin concentration in a cleavage ring occurred at late anaphase, just before furrowing could be detected. Initially, the intensity of fluorescence and the width of the fluorescent ring increased as the ring constricted. In cells with asymmetrically positioned mitotic spindles, both protein concentration and furrowing were first evident in the cortical regions closest to the equator of the mitotic spindle. As cytokinesis progressed in such asymmetrically dividing cells, fluorescent actin and myosin appeared at the opposite side of the cell just before furrowing activity could be seen there. At the end of cytokinesis, myosin and actin were concentrated beneath the membrane of the midbody and subsequently became organized in two rings at either end of the midbody.

Impact of Toll-like receptors [TLR] 2 (-196 to -174 del) and TLR 4 (Asp299Gly, Thr399Ile) in cervical cancer susceptibility in North Indian women

OBJECTIVE(S)

Targeting the Toll-like receptor (TLR) signaling pathway in elucidating the cellular and molecular mechanisms of human diseases, including cervical cancer, is gaining tremendous importance. The aim of our study was to identify the role of TLR 2(-196 to -174 del) and TLR 4(Asp299Gly and Thr399Ile) gene polymorphisms in cervical cancer susceptibility in North Indian women.

METHODS

For the study, blood samples were collected from histopathologically confirmed patients of cervical cancer (n=150) and unrelated, healthy female controls of similar ethnicity (n=150). Genomic DNA was extracted from peripheral blood leukocytes using salting-out method. TLR 2 and TLR 4 genotyping was done using Polymerase Chain Reaction and Restriction Fragment Length Polymorphism followed by 10% polyacrylamide gel electrophoresis.

RESULTS

TLR 2 del allele showed significant association (p=0.048, OR=1.6 [95%CI=1.00-2.51]) with cervical cancer susceptibility, while no significant association was found with TLR 4 (Asp299Gly and Thr399Ile). However, TLR 4 Thr/Ile genotype was found to be significantly associated with early stage (Stage II) of cervical cancer (p=0.044, OR=2.51 [95%CI=1.03-6.12]). Furthermore, TLR 2 ins/del genotype showed strong association (p=0.015, OR=1.95 [95%CI=1.14-3.33]) with tobacco usage in women with cervical cancer.

CONCLUSION(S)

Our study highlighted the involvement of TLR 2 (-196 to -174 del) and TLR 4 (Thr399Ile) gene polymorphisms in cervical cancer susceptibility. The TLR gene polymorphisms, upon further evaluation, may be helpful in elucidation of immunobiological mechanisms associated with cervical cancer susceptibility.

Common genetic variants in pre-microRNAs and risk of gallbladder cancer in North Indian population

MicroRNAs (miRNAs) are small, non-coding RNA molecules that function as negative regulators of gene expression. Common genetic variants (single nucleotide polymorphisms, SNPs) in miRNA genes may alter their expression or maturation resulting in varied functional consequences. Present case-control study evaluated the potential association of three SNPs (rs2910164, rs11614913 and rs3746444) in pre-miRNAs with gallbladder cancer (GBC) risk in 230 GBC cases and 230 controls in a North Indian population. Odds ratio (OR) and 95% confidence interval (95% CI) were calculated for the association of individual SNPs and their interactions with GBC. A non-significant increased risk was observed between carriers of variant genotypes of rs2910164, rs11614913 and rs3746444 (ORs=1.3, 1.3 and 1.1, respectively). This increased risk was more profound in GBC patients with gallstones (ORs=1.4, 1.6 and 1.1, respectively). To further evaluate the cumulative effects of the variant allele, we did a combined unfavorable genotype analysis, which showed a borderline statistical significance. In comparison with the low-risk group (0-2 variant alleles), the high-risk group (>2 variant alleles) had a 1.7-fold (95% CI=1.0-2.8) increased risk for GBC (P(trend)=0.056). These findings suggest, for the first time, that common miRNA variants may not contribute to GBC susceptibility in North Indian population.

Visualization of myosin in living cells

Myosin light chains labeled with rhodamine are incorporated into myosin-containing structures when microinjected into live muscle and nonmuscle cells. A mixture of myosin light chains was prepared from chicken skeletal muscle, labeled with the fluorescent dye iodoacetamido rhodamine, and separated into individual labeled light chains, LC-1, LC-2, and LC-3. In isolated rabbit and insect myofibrils, the fluorescent light chains bound in a doublet pattern in the A bands with no binding in the cross-bridge-free region in the center of the A bands. When injected into living embryonic chick myotubes and cardiac myocytes, the fluorescent light chains were also incorporated along the complete length of the A band with the exception of the pseudo-H zone. In young myotubes (3-4 d old), myosin was localized in aperiodic as well as periodic fibers. The doublet A band pattern first appeared in 5-d-old myotubes, which also exhibited the first signs of contractility. In 6-d and older myotubes, A bands became increasingly more aligned, their edges sharper, and the separation between them (I bands) wider. In nonmuscle cells, the microinjected fluorescent light chains were incorporated in a striated pattern in stress fibers and were absent from foci and attachment plaques. When the stress fibers of live injected cells were disrupted with DMSO, fluorescently labeled myosin light chains were present in the cytoplasm but did not enter the nucleus. Removal of the DMSO led to the reformation of banded, fluorescent stress fibers within 45 min. In dividing cells, myosin light chains were concentrated in the cleavage furrow and became reincorporated in stress fibers after cytokinesis. Thus, injected nonmuscle cells can disassemble and reassemble contractile fibers using hybrid myosin molecules that contain muscle light chains and nonmuscle heavy chains. Our experiments demonstrate that fluorescently labeled myosin light chains from muscle can be readily incorporated into muscle and nonmuscle myosins and then used to follow the dynamics of myosin distribution in living cells.

Cytochrome P450 in Cancer Susceptibility and Treatment

Cytochrome 450 (CYP450) designates a group of enzymes abundant in smooth endoplasmic reticulum of hepatocytes and epithelial cells of small intestines. The main function of CYP450 is oxidative catalysis of various endogenous and exogenous substances. CYP450 are implicated in phase I metabolism of 80% of drugs currently in use, including anticancer drugs. They are also involved in synthesis of various hormones and influence hormone-related cancers. CYP450 genes are highly polymorphic and their variants play an important role in cancer risk and treatment. Association studies and meta-analyses have been performed to decipher the role of CYP450 polymorphisms in cancer susceptibility. Cancer treatment involves multimodal therapies and evaluation of CYP450 polymorphisms is necessary for pharmacogenetic assessment of anticancer therapy outcomes. In addition, CYP450 inhibitors are being evaluated for improved pharmacokinetics and oral formulation of several anticancer drugs.

Evaluation of Toll-like receptors 3 (c.1377C/T) and 9 (G2848A) gene polymorphisms in cervical cancer susceptibility

Cervical cancer is emerging as a leading cause of morbidity and mortality in women worldwide. Toll-like Receptor (TLR) gene polymorphisms may contribute to subsequent inter-individual variability in cancer susceptibility. The present study aimed to identify the role of TLR 3 (c.1377C/T) [rs3775290] and TLR 9 (G2848A) [rs352140] gene polymorphisms in the risk of developing cervical cancer in North India. Peripheral blood samples were collected from 200 histopathologically confirmed cervical cancer patients from North India and 200 unrelated, cancer-free, age-matched healthy female controls of similar ethnicity. Genomic DNA was extracted using the salting-out method, and genotyped for TLR 3 and TLR 9 using polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP). Our data demonstrated a lack of association between TLR 3 (c.1377C/T) and TLR 9 (G2848A) gene polymorphisms and the risk of developing cervical cancer. TLR 3 CT + TT was marginally associated (P = 0.061; age-adjusted OR = 1.46; 95% CI = 0.98-2.16) with cervical cancer susceptibility. The AA genotype of TLR 9 showed borderline significance (P = 0.053) conferring a marginal increased risk (OR = 2.63, 95%CI = 0.99-7.01) for advanced cancer stages (III + IV). Further, TLR 3 and 9 polymorphisms did not have a significant role in modulation of risk due to tobacco usage in cervical cancer patients. Our study suggests only marginal role of TLR 3 and 9 gene polymorphisms in cervical cancer susceptibility in North India; however, future studies in ethnically diverse populations may provide a more comprehensive involvement of innate immunity in cervical cancer etiology in women worldwide.

Differential role of sodium channels SCN1A and SCN2A gene polymorphisms with epilepsy and multiple drug resistance in the north Indian population

AIMS

To evaluate sodium channel genes as candidates for epilepsy susceptibility and their role in therapeutic efficacy, we screened coding single-nucleotide polymorphism of SCN1A p. Thr 1067 Ala or c.3184 A-->G (rs2298771) and SCN2A p.Arg19Lys or c.56 G-->A (rs17183814) in north Indian epilepsy patients.

METHODS

The genotyping was performed in 160 control subjects and 336 patients with epilepsy, of whom 117 were drug resistant and 219 were drug responsive. Therapeutic drug monitoring for phenytoin, carbamazepine, phenobarbital and valproate was also performed in 20% of the patients to confirm compliance.

RESULTS

AG genotype of SCN1A 3184 A-->G polymorphism was significantly higher and associated in epilepsy patients [P= 0.005; odds ratio (OR) 1.76, 95% confidence interval (CI) 1.19, 2.61], whereas A variant of SCN2A c.56 G-->A was associated with multiple drug resistance in north Indian patients with epilepsy (P= 0.03; OR 1.62, 95% CI 1.03, 2.56).

CONCLUSIONS

Overall, results indicate a differential role of genetic polymorphisms of sodium channels SCN1A and SCN2A in epilepsy susceptibility and drug response.

Candidate gene studies in gallbladder cancer: a systematic review and meta-analysis

Gallbladder cancer (GBC) is the most frequent biliary tract malignancy. Wide variations in GBC incidence and familial and epidemiological data suggest involvement of a genetic component in its etiopathogenesis. A systematic review of genetic association studies in GBC was performed by applying a meta-analysis approach and systematically reviewing PubMed database using appropriate terms. Odds ratios (ORs) and 95% confidence intervals (CIs) were appropriately derived for each gene-disease association using fixed and random effect models. Meta-regression with population size and genotyping method was also performed. Study quality was assessed using a 10-point scoring system designed from published guidelines. Following a review of 44 published manuscripts and one unpublished report, 80 candidate gene variants and 173 polymorphisms were analyzed among 1046 cases and 2310 controls. Majority of studies were of intermediate quality. Four polymorphisms with >3 separate studies were included in the meta-analysis [OGG1 (rs1052133), TP53 (rs1042522), CYP1A1 (rs1048943) and GSTM1 null polymorphism]. The meta-analysis demonstrated no significant associations of any of the above polymorphisms with GBC susceptibility except TP53 (rs1042522) polymorphism. To conclude, existing candidate gene studies in GBC susceptibility have so far been insufficient to confirm any association. Future research should focus on a more comprehensive approach utilizing potential gene-gene, gene-environment interactions and high-risk haplotypes.

Association of Toll-like receptor-4 (Asp299Gly and Thr399Ileu) gene polymorphisms with gastritis and precancerous lesions

A Toll-like receptor-4 (TLR-4) Asp299Gly and Thr399Ileu substitution reduces responsiveness to Helicobacter pylori (H. pylori) lipopolysaccharide. CagA+ strains of H. pylori are known to be associated with gastroduodenal diseases. Therefore we aimed to evaluate association of TLR-4 substitutions and CagA seropositivity with gastritis and precancerous lesions in a northern Indian population. After upper gastrointestinal endoscopy, 130 rapid urease test (RUT)-positive patients with nonulcer dyspepsia (NUD) were included. Patients with NUD were also screened for H. pylori infection using modified Giemsa staining and anti-CagA IgG enzyme-linked immunoabsorbent assay. All patients and 200 asymptomatic control subjects were genotyped for TLR-4 substitutions using polymerase chain reaction-restriction fragment length polymorphism. We observed that frequencies of TLR-4 Asp299Gly variants were comparable between patients and control subjects, and also between positive and negative groups of precancerous lesions in patients. Frequencies of TLR-4 399Ileu allele (8% vs 3%, p = 0.008) and Asp299-Ileu399 haplotype (6.5% vs 3%, p = 0.022) were higher in patients than in control subjects at risk for gastritis (OR = 2.6 and 2.5, respectively). TLR-4 399Ileu allele carriers had higher risk for plasma cell infiltration (p = 0.023, OR = 10.6) that led to atrophy (p = 0.028, OR = 4.2) and intestinal metaplasia (p = 0.009, OR = 4.7). CagA positivity was more frequently associated with lymphoid follicle formation (p = 0.033, OR = 2.53). In conclusion TLR-4 Thr399Ileu substitution may be a risk factor for gastritis and precancerous lesions. CagA positivity may be a risk factor for lymphoid follicle development but not for other precancerous lesions in a northern Indian population.

Formation of myofibrils in spreading chick cardiac myocytes

Cardiac myocytes were isolated from 5-6-day-old chick embryos and allowed to spread in culture. The distribution of alpha-actinin in the cells was followed for five days in culture by exposing permeabilized cells to rhodamine-labeled alpha-actinin and also by injecting the labeled alpha-actinin into living myocytes. In addition to labeling the Z bands of sarcomeres, the added alpha-actinin also labeled small particles that were usually arranged periodically in linear arrays with a spacing between particles of 0.3-2.0 micron. Actin was localized between the particles of alpha-actinin by means of fluorescein-labeled heavy meromyosin. The punctate localization of alpha-actinin was prominent in pseudopods, behind ruffles, and at the periphery of spreading cells. Long rows of particles of alpha-actinin were often parallel to one another with the alpha-actinin particles in register. These linear arrays appeared to merge laterally to form strands with broader concentrations of alpha-actinin. Other linear arrays were parallel to myofibrils in the cell and some extended outward from the ends of myofibrils. We conclude that during spreading of cardiac myocytes, myofibrils form at the cell periphery behind the extending margins of the cell, and that the aggregates of alpha-actinin found in these areas are nascent Z bands in the forming myofibrils.

Genetic polymorphism of glutathione S-transferase genes (GSTM1, GSTT1 and GSTP1) and susceptibility to prostate cancer in Northern India

OBJECTIVE

To examine the association of glutathione-S-transferase (GST) gene polymorphisms in patients with sporadic prostate cancer, in a North Indian population, as GSTs are active in detoxifying a wide variety of endogenous or exogenous carcinogens, and genetic polymorphisms of GSTM1, GSTT1 and GSTP1 have been assessed to evaluate the relative risk of various cancers.

PATIENTS AND METHODS

We assessed 127 patients with prostate cancer and 144 age-matched controls, all from North India. The GSTT1 and GSTM1 null genotypes were identified by multiplex polymerase chain reaction (PCR) in peripheral blood DNA samples, and GSTP1-313 A/G polymorphism was determined by PCR/restriction fragment length polymorphism.

RESULTS

There was a significant association in null alleles of the GSTM1 (odds ratio 2.239, 95% confidence interval 1.37-3.65, P = 0.001) and GSTT1 (1.891, 1.089-3.282, P = 0.026) with prostate cancer risk, and in the -313 G alleles (Val) of the GSTP1 gene (2.48, 1.51-4.08, P < 0.001). The combined analysis of these three genotypes showed a further increase in the risks of prostate cancer (7.23, 2.42-22.6, P < 0.001).

CONCLUSION

The GSTP1-313 G polymorphism, and null alleles of GSTM1 and GSTT1, are strong predisposing risk factors for sporadic prostate cancer in North India.

Association of genetic polymorphism of glutathione S-transferase M1, T1, P1 and susceptibility to bladder cancer

OBJECTIVE

Glutathione-S-transferases (GSTs) are active in the detoxification of wide variety of endogenous or exogenous carcinogens. We examined the association of the GST gene polymorphism with sporadic bladder cancer patients in Northern India.

MATERIAL AND METHODS

The study constituted of 106 bladder cancer cases and 370 age-matched controls. The GSTT1 and GSTM1 null genotypes were identified by multiplex PCR and GSTP1313 A/G by Polymerase Chain Reaction/Restriction Fragment Length Polymorphism method (PCR/RFLP).

RESULTS

We observed non-significant association in null alleles of the GSTM1 (p = 0.611, OR = 1.12, 95% CI = 0.72-1.74 and GSTT1 (p = 0.135, OR = 1.45, 95% CI = 0.89-2.37) with risk of bladder cancer. However, the G/G genotype of the GSTP1 gene polymorphism was highly significant when compared to controls (p=0.000, OR = 7.12, 95% CI = 3.14-16.16). The combined analysis of the three risk genotypes demonstrated further increase in the risk of bladder cancer (p = 0.000, OR = 7.29 95% CI = 2.81-18.93).

CONCLUSION

Our study demonstrated that GSTP1313 G/G polymorphism is a strong predisposing risk factor for bladder cancer. Combination of three GST genotypes association exhibiting gene-gene interaction further substantiates the increased risk of bladder cancer.

Genetic and functional identification of the likely causative variant for cholesterol gallstone disease at the ABCG5/8 lithogenic locus

The sterolin locus (ABCG5/ABCG8) confers susceptibility for cholesterol gallstone disease in humans. Both the responsible variant and the molecular mechanism causing an increased incidence of gallstones in these patients have as yet not been identified. Genetic mapping utilized patient samples from Germany (2,808 cases, 2,089 controls), Chile (680 cases, 442 controls), Denmark (366 cases, 766 controls), India (247 cases, 224 controls), and China (280 cases, 244 controls). Analysis of allelic imbalance in complementary DNA (cDNA) samples from human liver (n = 22) was performed using pyrosequencing. Transiently transfected HEK293 cells were used for [(3) H]-cholesterol export assays, analysis of protein expression, and localization of allelic constructs. Through fine mapping in German and Chilean samples, an ∼250 kB disease-associated interval could be defined for this locus. Lack of allelic imbalance or allelic splicing of the ABCG5 and ABCG8 transcripts in human liver limited the search to coding single nucleotide polymorphisms. Subsequent mutation detection and genotyping yielded two disease-associated variants: ABCG5-R50C (P = 4.94 × 10(-9) ) and ABCG8-D19H (P = 1.74 × 10(-10) ) in high pairwise linkage disequilibrium (r(2) = 0.95). [(3) H]-cholesterol export assays of allelic constructs harboring these genetic candidate variants demonstrated increased transport activity (3.2-fold, P = 0.003) only for the ABCG8-19H variant, which was also superior in nested logistic regression models in German (P = 0.018), Chilean (P = 0.030), and Chinese (P = 0.040) patient samples.

CONCLUSION

This variant thus provides a molecular basis for biliary cholesterol hypersecretion as the mechanism for cholesterol gallstone formation, thereby drawing a link between "postgenomic" and "pregenomic" pathophysiological knowledge about this common complex disorder. (HEPATOLOGY 2012).

Observations of microfilament bundles in living cells microinjected with fluorescently labelled contractile proteins

Fluorescently labelled contractile proteins (alpha-actinin and filamin) were used to study the dynamic nature of three types of microfilament bundles: myofibrils, stress fibres and polygonal networks. Cultured muscle and non-muscle cells that were microinjected with fluorescent alpha-actinin rapidly incorporated the labelled protein into Z-bands, stress fibre densities and the polygonal foci. Living, injected cells were then observed for varying periods of time, and changes in orientation and periodicity of the myofibrils, stress fibres and polygonal networks were recorded. Permeabilized cells were also reacted with fluorescently labelled proteins and with contractile protein antibodies in order to analyse further the changes taking place in the myofibrils and stress fibres. In both living cardiac myocytes and living skeletal muscle myotubes, contractile myofibrils were present in the same cell with non-contractile nascent myofibrils. The periodicities of small Z-bodies in the nascent non-contractile myofibrils were shorter than the Z-band spacings in the contractile myofibrils, yet both types of myofibrils contained muscle myosin. Over a period of 24 h, a nascent myofibril in a living, microinjected myotube was observed to grow from Z-body spacings of 0.9-1.3 micron to full sarcomere spacings (2.3 microns). During the same time, nascent myofibrils appeared de novo and Z-band alignment became more ordered in the fully formed myofibrils. Stress fibres were not observed to undergo the predictable type of growth seen in myofibrils, but stress fibre periodicities did change in some fibres; some shortened while others lengthened. The orientation of fibres shifted in cytoplasm of both mobile cells and stationary cells. Attachment plaques and foci also changed position and in some cases subdivided and/or disappeared. Models of stress fibres and polygonal networks are presented that suggest that the changes in the periodicities of the dense bodies in stress fibres and the distances between polygonal foci are related to the movement of the interdigitating actin and myosin filaments.

No association of ABCB1 polymorphisms with drug-refractory epilepsy in a north Indian population

Multiple drug resistance is a common problem in the treatment of epilepsy, and approximately 30% of patients continue to have seizures despite all therapeutic interventions. Among various classes of drug transporters, genetic variants of P-glycoprotein (P-gp) encoded by the ABCB1 (ATP-binding cassette subfamily B member 1) gene have been associated with drug-refractory epilepsy. Our aim was to investigate the effect of the 1236C>T(rs1128503), 2677G>T/A(rs2032582), and 3435C>T(rs1045642) single-nucleotide polymorphisms of ABCB1 (or MDR1) on drug resistance in north Indian patients with epilepsy. Genotyping was performed in 101 control subjects and 325 patients with epilepsy, of whom 94 were drug resistant and 231 drug responsive. Therapeutic drug monitoring for phenytoin, carbamazepine, phenobarbital, and valproate was also performed to confirm compliance in 20% of the patients. Genotype and haplotype frequencies of these polymorphisms did not differ between drug-resistant and drug-responsive patients. Our results demonstrate ABCB1 polymorphisms are not associated with drug resistance in north Indian epileptic patients.

GSTT1, GSTM1 and GSTP1 genetic polymorphisms and interaction with tobacco, alcohol and occupational exposure in esophageal cancer patients from North India

Glutathione S-transferases(GSTs) are detoxification enzymes that provide critical defense against carcinogens. Our hypothesis was that altered frequencies of GST genotypes and environmental exposures might be associated with increased susceptibility for the development of esophageal cancer. A total of 100 esophageal cancer patients and 137 age and gender matched healthy controls were analyzed for GST polymorphisms. Frequencies of GSTT1 null, GSTM1 null and GSTP1 genotypes did not differ between patients and controls. However, a two-fold risk was observed for GSTM1 null genotype in adenocarcinoma (OR(odds ratio) 2.1; 95% CI(confidence intervals)=0.53-8.6). Further, we used a case only design to study gene-environment interactions in esophageal cancer. In patients with smoking habits, GSTM1 null and GSTP1 ile/ile genotype were at higher risk for esophageal cancer (OR 1.5; 95% CI=0.50-4.4 and OR 1.3; 95% CI=0.40-3.5), respectively. A moderate risk for cancer was observed from alcohol usage along with GSTM1 null(OR 1.3; 95% CI=0.50-3.6) and GSTP1 val/val genotypes(OR 1.2; 95% CI=0.20-5.7). Interaction of GST genotypes with occupational exposure did not affect risk for esophageal cancer. These findings suggest that genetic polymorphisms of GSTT1, GSTM1, and GSTP1 are not associated with higher risk of esophageal cancer. However, interaction of smoking or alcohol with GSTM1 null or GSTP1 ile/ile moderately increases the risk for esophageal cancer in North Indian population.

Stress fiber and cleavage furrow formation in living cells microinjected with fluorescently labeled alpha-actinin

alpha-Actinins, isolated from muscle and nonmuscle sources and labeled with various fluorescent dyes, were microinjected into living PtK2 cells during interphase to observe the reformation of stress fibers following cell division. Fluorescently labeled ovalbumin and bovine serum albumin were also injected as control proteins. alpha-Actinin was incorporated into stress fibers within 5 minutes after injection and remained present in the fibers for up to 11 days. The pattern of incorporation was the same regardless of whether the alpha-actinin was isolated from muscle or nonmuscle tissues or whether it was labeled with fluorescein, Lucifer Yellow, or rhodamine dyes. In contrast, neither labeled ovalbumin nor bovine serum albumin were incorporated into stress fibers. When the injected cells entered prophase, all stress fibers disassembled, resulting in a distribution of the fluorescent alpha-actinin throughout the cytoplasm. During cytokinesis, the fluorescent alpha-actinin was concentrated in the broad area between the separated chromosomes and along the edge of the cell in the cleavage area. Within 10 minutes after the completion of cleavage, the first fluorescent stress fibers reformed parallel to the spreading edges of the daughter cells and in close association with the midbody with a concomitant loss of alpha-actinin in the former cleavage furrow. Additional fibers formed adjacent to these first stress fibers. In some cases, new stress fibers formed between two existing stress fibers and some stress fibers moved up to 4 micron apart from one another in the course of 2 hours. Thus, fluorescent alpha-actinin, injected into living cells, undergoes the same cyclical changes in distribution as endogenous alpha-actinin during the cell cycle: from stress fibers to cleavage furrow and back to stress fibers.

Oxidative stress in non-small cell lung cancer patients after chemotherapy: association with treatment response

Levels of lipid peroxidation, nitric oxide and glutathione, as well as superoxide dismutase activity were evaluated in non-small cell lung cancer patients before and after chemotherapy. Oxidative stress was shown to influence treatment efficacy and survival of these patients.

BACKGROUND AND OBJECTIVE

The aim of this study was to assess the level of oxidative stress after chemotherapy in non-small cell lung cancer patients, and its association with treatment response and survival.

METHODS

Two hundred and three previously untreated non-small cell lung cancer patients and 150 healthy subjects were selected for the study. Patients received cisplatin+etoposide, and were followed for up to six cycles, for evaluation of oxidative stress. Blood levels of lipid peroxidation products (LPO), glutathione (GSH) and nitric oxide (NO), and superoxide dismutase (SOD) activity were measured at day 0 and after the third and sixth cycles of chemotherapy. Response and survival were measured at the end of follow up. Survival was estimated by the Kaplan-Meier method using the log-rank test.

RESULTS

In the patients, pretreatment levels of LPO and NO were low, while GSH and SOD levels were high compared with those after the third and sixth cycles of chemotherapy. Among the 203 patients, there were 51 deaths, 82 non-responders and 70 responders at the end of the sixth cycle. Overall mean survival was higher among responders than non-responders (24.6 vs 21.2 weeks, P<0.01). The hazard ratio was 2.4 (95% CI: 1.3-3.77). Pretreatment levels of oxidative stress were similar among responders and non-responders (P>0.05). After the third and sixth cycles of chemotherapy, LPO and NO levels were low (P<0.05 or P<0.01) and GSH levels and SOD activity were high (P<0.05 or P<0.01) in responders as compared with non-responders.

CONCLUSIONS

In lung cancer patients, oxidative stress increased and anti-oxidant enzymes decreased as the disease progressed. Chemotherapy may suppress oxidative stress and decreased anti-oxidant enzyme activity in responders as compared with non-responders. These effects may contribute to improved survival among responders.

Significant association between toll-like receptor gene polymorphisms and gallbladder cancer

BACKGROUND

Toll-like receptors (TLRs) are evolutionarily conserved cell surface receptors of innate immune system. Various polymorphisms in TLR genes have been identified and associated with susceptibility toward various malignancies such as prostate cancer, gastric cancer and colorectal cancer. The present study was undertaken to examine the potential association of two polymorphisms in TLR2 and TLR4 genes with gallbladder cancer (GBC) susceptibility.

METHODS

Genotypes and allelic frequencies of TLR2 and TLR4 gene polymorphisms were determined for 233 GBC patients and 257 cancer-free controls randomly selected from the population, using polymerase chain reaction-restriction fragment length polymorphism. Odds ratio (OR) and 95% confidence interval (95% CI) were calculated in a multivariate logistic regression analysis for the association of TLR polymorphisms with GBC.

RESULTS

'del' allele carriers of TLR2 (Delta22) polymorphism were associated with a 1.54-fold increased risk for GBC (95% CI=1.02-2.24; P(trend)=0.091). The TLR4 Ex4+936C >T polymorphism (g.14143C>T; rs4986791) was also found to be significantly associated with the overall higher risk of GBC under a dominant mode of inheritance (OR=1.96; 95% CI=1.11-2.26; P(trend)=0.021). The false-positive report probability (FPRP) approach advocated that these results were noteworthy (FPRP<0.5). Subgroup analysis showed that TLR4 Ex4+936C>T polymorphism was associated with an increased risk of GBC in females and GBC cases with gallstones (OR=2.85 and 2.22 respectively).

CONCLUSION

In summary, low-penetrance variants in TLR genes may alter the susceptibility towards gallbladder cancer.

An N-terminal fragment of titin coupled to green fluorescent protein localizes to the Z-bands in living muscle cells: overexpression leads to myofibril disassembly

Cultures of nonmuscle cells, skeletal myotubes, and cardiomyocytes were transfected with a fusion construct (Z1.1GFP) consisting of a 1.1-kb cDNA (Z1.1) fragment from the Z-band region of titin linked to the cDNA for green fluorescent protein (GFP). The Z1.1 cDNA encodes only 362 amino acids of the approximately 2000 amino acids that make up the Z-band region of titin; nevertheless, the Z1.1GFP fusion protein targets the alpha-actinin-rich Z-bands of contracting myofibrils in vivo. This fluorescent fusion protein also localizes in the nascent and premyofibrils at the edges of spreading cardiomyocytes. Similarly, in transfected nonmuscle cells, the Z1.1GFP fusion protein localizes to the alpha-actinin-containing dense bodies of the stress fibers in vivo. A dominant negative phenotype was also observed in living cells expressing high levels of this Z1.1GFP fusion protein, with myofibril disassembly occurring as titin-GFP fragments accumulated. These data indicate that the Z-band region of titin plays an important role in maintaining and organizing the structure of the myofibril. The Z1.1 cDNA was derived from a chicken cardiac lambda gt11 expression library, screened with a zeugmatin antibody. Recent work has suggested that zeugmatin is actually part of the N-terminal region of the 81-kb titin cDNA. A reverse transcriptase polymerase chain reaction using a primer from the distal end (5' end) of the Z1.1 zeugmatin cDNA and a primer from the nearest known proximal (3' end) chicken titin (also called connectin) cDNA resulted in a predicted 0.3-kb polymerase chain reaction product linking the two known chicken titin cDNAs to each other. The linking region had a 79% identity at the amino acid level to human cardiac titin. This result and a Southern blot analysis of chicken genomic DNA hybridized with Z1.1 add further support to our original suggestion that zeugmatin is a proteolytic fragment from the N-terminal region of titin.

Single-nucleotide polymorphisms of DNA repair genes OGG1 and XRCC1: association with gallbladder cancer in North Indian population

BACKGROUND

DNA damage by endogenous or exogenous source of reactive oxygen species (ROS) plays an important role in induction and progression of various cancers. Physiologically, gallbladder is likely to be exposed to various ROS which leads to extensive DNA damage. Cells overcome the DNA damage by repair mechanisms. Genetic variants of OGG1 and XRCC1, important enzymes participating in base excision repair pathway, may confer interindividual variations in susceptibility to gallbladder cancer (GBC). This study was aimed to examine the role of OGG1 Ser326Cys (rs1052133) and XRCC1 Arg194Trp (C > T) (rs25487) and Arg399Gln (G > A) (rs1799782) polymorphisms in GBC susceptibility.

METHODS

The study included 173 GBC patients and 204 controls. Genotyping was done by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method. Differences in the frequencies were estimated by chi-square test and risk was estimated by using unconditional logistic regression after adjusting for age and gender.

RESULTS

OGG1 Cys/Cys genotype frequency was significantly higher in GBC patients [odds ratio (OR) = 2.93; 95% confidence interval (CI) = 1.14-7.51]. The increased risk was more pronounced in female GBC patients (OR = 5.92; 95%CI = 1.20-29.13), patients with gallstone (OR = 5.50; 95%CI = 1.99-15.16), female gender, and late onset of disease (OR = 4.72, 95%CI = 1.43-15.53). In XRCC1 Arg399Gln polymorphism, significant differences in frequencies of Gln/Gln and Arg/Gln genotypes conferred significantly low risk for GBC (OR = 0.62; 95%CI = 0.39-0.97 and OR = 0.37; 95%CI = 0.19-0.71 respectively). However, XRCC1 Arg194Trp polymorphism was not associated with GBC. The carriers of Arg-Gln haplotype consisting of 194Arg and 399Gln alleles of XRCC1 were also at significant low risk for GBC (OR = 0.59, 95%CI = 0.42-0.82). Interaction of genotypes and tobacco usage did not modulate the risk.

CONCLUSION

Results suggest that Cys/Cys genotype of OGG1 Ser326Cys polymorphism is associated with increased risk of GBC. However, Arg399Gln polymorphism and Arg-Gln haplotype comprising XRCC1 Arg194Trp and Arg399Gln polymorphisms conferred low risk for GBC susceptibility.