SEARCH · PubMed Health

Results for “Pathway informed transformer”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24Linked to original sources

PubMed1989

Functional organization of mustached bat inferior colliculus: II. Connections of the FM2 region.

Echolocating bats estimate target distance by analyzing the time delay between frequency-modulated portions of their emitted ultrasonic vocalizations and the resultant echoes. In the companion paper we investigated, in the central nucleus of the inferior colliculus, the representation of the predominant second-harmonic frequency-modulated component (FM2) of the mustached bat biosonar signal (O'Neill et al.: J. Comp. Neurol. 283:000-000,'89). In the present paper we report the connections of this part of the colliculus, as determined by focal, iontophoretic injections of HRP following single-unit mapping of the FM2 representation. It was found that the major inputs to the FM2 region of the inferior colliculus come from the contralateral cochlear nucleus; ipsilaterally from the medial superior olive, periolivary nuclei, and ventral and intermediate nuclei of the lateral lemniscus; and bilaterally from the lateral superior olive and dorsal nucleus of the lateral lemniscus. This study identifies for the first time those specific regions of brainstem nuclei providing input to the central nucleus of the inferior colliculus that process FM2 information in the mustached bat. The primary outputs of the FM2 region project to the medial and dorsal divisions of the medial geniculate body. In sharp contrast to other mammals, we found little evidence of connections to the ventral division of the medial geniculate. Other regions receiving significant inputs from the FM2 area include the deep superior colliculus ipsilaterally and the ipsilateral lateral pontine nuclei. Some fibers also terminated near the midline in the dorsal midbrain periaqueductal gray. Sparse intrinsic connections were also seen to the ipsilateral dorsoposterior division of the central nucleus and to the contralateral inferior colliculus at a location homologous to the injection site in the anterolateral division. The finding that FM2 projections to the medial geniculate heavily favor the medial and dorsal divisions is consistent with the location of "FM-FM" delay-dependent facilitation neurons found by Olsen (Processing of Biosonar Information by the Medical Geniculate Body of the Mustached Bat, Pteronotus parnellii. Dissertation, Washington Univ., St. Louis, '86) in these divisions, and with thalamocortical projection patterns in this species. These findings demonstrate that for the FM portions of the biosonar signal, a transformation from a tonotopic form of processing to a more specialized, convergent pattern of organization occurs at the level of the inferior colliculus outputs.

Animals↗

PubMed2000

Detailed reaction mechanism of macrophomate synthase. Extraordinary enzyme catalyzing five-step transformation from 2-pyrones to benzoates.

Macrophomate synthase from the fungus Macrophoma commelinae IFO 9570 is a Mg(II)-dependent dimeric enzyme that catalyzes an extraordinary, complex five-step chemical transformation from 2-pyrone and oxalacetate to benzoate involving decarboxylation, C-C bond formation, and dehydration. The catalytic mechanism of the whole pathway was investigated in three separate chemical steps. In the first decarboxylation step, the enzyme loses oxalacetate decarboxylation activity upon incubation with EDTA. Activity is fully restored by addition of Mg(II) and is not restored with other divalent metal cations. The dissociation constant of 0.93 x 10(-)(7) for Mg(II) and atomic absorption analysis established a 1:1 stoichiometric complex. Inhibition of pyruvate formation with 2-pyrone revealed that the actual product in the first step is a pyruvate enolate, which undergoes C-C bond formation in the presence of 2-pyrone. Incubation of substrate analogs provided aberrant adducts that were produced via C-C bond formation and rearrangement. This strongly indicates that the second step is two C-C bond formations, affording a bicyclic intermediate. Based on the stereospecificity, involvement of a Diels-Alder reaction at the second step is proposed. Incubation of the stereospecifically deuterium-labeled malate with 2-pyrones in the presence of malate dehydrogenase provided information for the stereochemical course of the reaction catalyzed by macrophomate synthase, indicating that the first decarboxylation provides pyruvate (Z)-[3-(2)H]enolate and that dehydration at the final step occurs with anti-elimination accompanied by concomitant decarboxylation. Examination of kinetic parameters in the individual steps suggests that the third step is the rate-determining step of the overall transformation.

Benzoates↗

PubMed2004

Chicken anemia virus induced apoptosis: underlying molecular mechanisms.

In 1990, the chicken anemia virus (CAV) genome was cloned by us and proven to be representative for CAV isolates worldwide. This genome contains unique promoter/enhancer replication elements and genes. Upon infection of its target cells, CAV replicates via a double-stranded (ds) DNA intermediate. From this ds CAV molecule, a single mRNA is transcribed, which encodes for three distinct proteins VP1, VP2, and VP3 or apoptin. Its capsid contains only the VP1 protein. However, for the production of the neutralizing epitope, co-synthesis of VP1 and VP2 are needed. CAV genomes with mutations in the 12 bp insert of the promoter/enhancer region were shown to produce immunogenic functional CAV particles. Mutations in these and other regulatory elements of CAV might also decrease its virus load resulting in a reduced pathogenic effect. CAV causes fatal cytopathogenic effects in e.g. chicken thymocytes via apoptosis. Under in vitro conditions, CAV replicates only in transformed chicken cell lines, which indicates that at least a part of the CAV life-cycle requires transformed-like cellular events. In these transformed cell lines, the synthesis of the apoptin protein alone mimics the CAV-induced apoptosis, whereas the VP2 protein also harbors some apoptotic activity. Extensive studies on apoptin resulted in the characterization of domains essential for its apoptotic activity and nuclear localization, which seems to be related with its ability to induce apoptosis. Therefore, both VP2 and apoptin are of interest in reducing the pathogenicity of CAV infections. A series of biomedical studies on apoptin have been carried out in human cell systems, which are informative about the mechanism of CAV-induced apoptosis in chicken (transformed) cells. Synthesis of apoptin alone induces apoptosis in various human transformed and/or tumorigenic cell lines, but not in normal human diploid cells. A striking difference in the cellular localization of apoptin was observed in human normal diploid cells versus tumor cells. In all tumor cells, apoptin is located mainly in the heterochromatic regions of the nucleus, whereas in normal cells it is present in peri-nuclear structures. Apoptin contains a bipartite nuclear localization signal, and one domain that resemble a nuclear export signal. Elucidation of parts of the apoptin-induced apoptotic pathway revealed unique characteristics: apoptin-induced apoptosis is independent of the tumor suppressor p53. The anti-apoptotic protein Bcl-2 does not inhibit but even accelerates apoptin-induced apoptosis in tumor cells, whereas over expression of Bcl-2 in normal cells has no effect on the apoptin activity. Upstream caspases are not involved, whereas downstream caspase 3 is, but seems not to be essential. A number of novel proteins were shown to interact with apoptin in transformed cells. Future studies of apoptin, VP2 and related cellular proteins in chicken cells will unravel the regulatory aspects of CAV-induced apoptosis.

Animals↗

PubMed2003

Transformation of flavonoids by intestinal microorganisms.

Fruit, vegetables and cereals contain a wealth of secondary plan metabolites which have been implicated in the promotion of health. To understand the mechanism of their action it is necessary to gain more information on their fate in the body following ingestion. A certain proportion of ingested secondary plant constituents may escape absorption in the small intestine and therefore undergo transformation by intestinal microorganisms or enterohepatic circulation. To study the transformation of secondary plant metabolites by bacteria, Eubacterium ramulus was isolated from human feces and incubated with selected flavonoids. E. ramulus is a strictly anaerobic bacterium which was found to be present in the gastrointestinal tract of most individuals investigated. E. ramulus cleaves the ring system of several flavonols and flavones giving rise to the corresponding hydroxyphenylacetic and hydroxyphenylpropionic acids, respectively, as well as acetate and butyrate. Degradation pathways were proposed based on the intermediates detected by high performance liquid chromatography (HPLC) and HPLC coupled with mass spectrometry (LC-MS) and the detection of enzymes that catalyze reactions such as taxifolin isomerization, phloretin hydrolysis and phloroglucinol reduction. The dearomatizing phloroglucinol reductase, presumably part of all flavonoid degradation pathways, was purified and characterized. The gene encoding phloretin hydrolase was cloned from a E. ramulus gene library taking advantage of a newly developed fluorescence test for activity screening. Moreover, a new intermediate was discovered and identified by MS and 1H and 13C NMR analysis as alphitonin. To investigate the degradational potential of E. ramulus under in vivo conditions, germfree rats were associated with E. ramulus. Following the intragastric application of quercetin-3-glucoside, urine and feces of gnotobiotic rats were analyzed for degradational products originating from quercetin-3-glucoside. In feces of rats monoassociated with E. ramulus, 3,4-dihydroxyphenylacetic acid was found, indicating that this organism is able to cleave quercetin under in vivo conditions. To investigate in which way the dietary flavonoid content affects the cell counts of E. ramulus in the human intestinal tract, twelve human subjects consumed a flavonoid-free diet for one week and at one point during this period a large dose of flavonoids. Fecal samples from both phases of the study were analyzed by in-situ hybridization for total bacterial counts and counts of E. ramulus. Total cell counts and the cell counts of E. ramulus decreased significantly during the flavonoid-free period, while there was an increase in the E. ramulus counts of up to 10-fold during the flavonoid-rich period indicating that dietary secondary plant metabolites may have an influence on the intestinal microflora. E. ramulus is also capable of converting the isoflavonoids genistein and daidzein to the products 2-(4-hydroxyphenyl)-propionic acid and O-desmethylangolensin, respectively.

Animals↗

PubMed2002

A protein sequence that can encode native structure by disfavoring alternate conformations.

The linear sequence of amino acids contains all the necessary information for a protein to fold into its unique three-dimensional structure. Native protein sequences are known to accomplish this by promoting the formation of stable, kinetically accessible structures. Here we describe a Pro residue in the center of the third transmembrane helix of the cystic fibrosis transmembrane conductance regulator that promotes folding by a distinct mechanism: disfavoring the formation of a misfolded structure. The generality of this mechanism is supported by genome-wide transmembrane sequence analyses. Furthermore, the results provide an explanation for the increased frequency of Pro residues in transmembrane alpha-helices. Incorporation by nature of such 'negative folding determinants', aimed at preventing the formation of off-pathway structures, represents an additional mechanism by which folding information is encoded within the evolved sequences of proteins.

Amino Acid Sequence↗

PubMed2003

Beyond homeosis--HOX function in morphogenesis and organogenesis.

Hox genes encode conserved transcription factors expressed along the antero-posterior axis of vertebrates and invertebrates. In both phyla, HOX proteins control the formation of specific structures in the segments where they are expressed. Because of the global effect they have on segment morphology, the Hox genes are said to control segment identity. Here we review the data available on how HOX proteins regulate their downstream targets and how they mediate the formation of segment-specific structures. Within the segment, the information provided by HOX proteins, tissue-specific transcription factors, and signaling pathway effectors becomes integrated at the enhancer of the target genes, resulting in their localized activation. In general, HOX proteins regulate the morphogenesis of specific organs indirectly by activating networks of transcription factors and signaling molecules, but they can also directly regulate the so-called realizator genes: genes that control the cell behaviors that induce morphogenesis. Here we review some of the Hox-activated networks, the most interesting realizator genes known to date, and summarize how organogenesis is affected in Hox mutants. These examples reveal that only a fraction of the transformations caused by Hox mutations are in fact homeotic (leading to the morphological transformation of a structure present in one segment into that present in another segment). In the cases where Hox gene mutants do not cause homeotic transformations, the wild-type function of the Hox gene is to activate specific cell behaviors (cell proliferation, survival, shape changes, and rearrangements) that lead to the morphogenesis of particular organs. This second non-homeotic function is common to vertebrates and invertebrates, and we argue that it may actually constitute the original HOX function.

Animals↗

PubMed1984

Maturation of the auditory brainstem response from birth through early childhood.

The various parameters of the auditory brainstem response (ABR) undergo distinct maturational transformations in early life. The multiplicity of observed changes suggests unique timetables for development of the contributing neural elements. Although the precise physioanatomic substrate of the ABR remains speculative, experimental manipulations and selective response measures have been utilized to elucidate the developmental process. Even at our current level of understanding, the ABR has proven to be a valuable tool for the study of functional development in the nervous system. In the perinatal period and early childhood, the ABR constitutes one of the most reliable measures of neural integrity in the cochlear and caudal brainstem pathway. As our knowledge expands, the ABR should continue to provide information on the neurological and audiological status of healthy and special risk populations.

Adult↗

PubMed2002

Roger S. Mitchell lecture. Uses of expression microarrays in studies of pulmonary fibrosis, asthma, acute lung injury, and emphysema.

Expression microarrays are a powerful tool that could provide new information about the molecular pathways regulating common lung diseases. To exemplify how this tool can be useful, selected examples of informative experiments are reviewed. In studies relevant to asthma, the cytokine interleukin-13 has been shown to produce many of the phenotypic features of this disease, but the cellular targets in the airways and the molecular pathways activated are largely unknown. We have used microarrays to begin to dissect the different transcriptional responses of primary lung cells to this cytokine. In experiments designed to identify global transcriptional programs responsible for regulating lung inflammation and pulmonary fibrosis, we performed microarray experiments on lung tissue from wild-type mice and mice lacking a member of the integrin family know to be involved in activation of latent transforming growth factor (TGF)-beta. In addition to identifying distinct cluster of genes involved in each of these processes, these studies led to the identification of novel pathways by which TGF-beta can regulate acute lung injury and emphysema. Together, these examples demonstrate how careful application and thorough analysis of expression microarrays can facilitate the discovery of novel molecular targets for intervening in common lung diseases.

Animals↗

PubMed2006

Quantitative analysis of phosphotyrosine signaling networks triggered by CD3 and CD28 costimulation in Jurkat cells.

The mechanism by which stimulation of coreceptors such as CD28 contributes to full activation of TCR signaling pathways has been intensively studied, yet quantitative measurement of costimulation effects on functional TCR signaling networks has been lacking. In this study, phosphotyrosine networks triggered by CD3, CD28, or CD3 and CD28 costimulation were analyzed by site-specific quantitative phosphoproteomics, resulting in identification of 101 tyrosine and 3 threonine phosphorylation sites and quantification of 87 sites across four cell states. As expected, CD3 stimulation induced phosphorylation of CD3 chains and upstream components of TCR pathways such as Zap70, while CD28 stimulation induced phosphorylation of CD28, Vav-1, and other adaptor proteins including downstream of tyrosine kinase 1, Grb2-associated protein 2 (Grap2), and Wiskott-Aldrich syndrome protein. CD3 and CD28 costimulation induced a complex response including decreased threonine phosphorylation in the ERK1 and ERK2 activation loops and increased phosphorylation of selected tyrosine sites on ERK1/2, p38, phospholipase C-gamma, Src homology 2 domain-containing transforming protein 1, Grap2, and Vav-1, potentiating T cell activation. Hierarchical clustering and self-organizing maps were used to identify modules of coregulated phosphorylation sites within the network. Quantitative information in our study suggests quantitative and qualitative contribution by costimulation of CD28 on CD3-stimulated TCR signaling networks via enhanced phosphorylation of phospholipase C-gamma/Src homology 2 domain-containing transforming protein 1/Grap2/Vav-1 and their effects on downstream components including MAPKs.

Adaptor Proteins, Signal Transducing↗

PubMed1994

Protein-tyrosine kinases: potential targets for anticancer drug development.

Protein-tyrosine kinases (PTKs) were originally discovered over a decade ago as the dominant transforming components of certain tumor viruses. Since then these enzymes have become recognized as important intracellular mediators of a variety of mitogenic signaling pathways, including those associated with several growth factor receptors. The strong correlation of aberrant or over-expressed PTKs with a number of proliferative diseases has raised the possibility that PTK inhibitors may afford new approaches toward anticancer therapeutics. To address this possibility, potent and specific PTK inhibitors are needed both as pharmacological probes to study PTK-dependent signaling and as potential antiproliferative agents in their own right. De novo design of PTK inhibitors is hampered by a lack of three dimensional information regarding PTKs or the interaction of inhibitors with the enzymes. Motifs for the design of new inhibitors are therefore frequently derived by modification of structural them identified in natural-product screens. Exemplary of this process is the Laboratory of Medicinal Chemistry's program to develop PTK inhibitors based on pharmacophores present in three natural-product PTK inhibitors: lavendustin A, erbstatin and piceatannol. As summarized in this report, such efforts have led to new inhibitors with increased potency and interkinase selectivity. Whether PTK inhibitors will ultimately prove to be useful as antiproliferative therapeutics remains an open question whose answer will be heavily reliant on a cooperative partnership among natural-product and medicinal chemists, pharmacologists and clinicians.

Drug Design↗

PubMed2006

Lipid-mediated introduction of hepatitis B virus capsids into nonsusceptible cells allows highly efficient replication and facilitates the study of early infection events.

The hepatitis B virus (HBV) is an enveloped DNA virus which is highly infectious in vivo. In vitro, only primary hepatocytes of humans and Tupaia belangeri or the novel HepaRG cell line are susceptible to HBV, but infection is inefficient and study of early infection events in single cells is unsatisfactory. Since hepatoma cells replicate the virus efficiently after transfection, this limited infection efficiency must be related to the initial entry phase. Here, we describe the lipid-based delivery of HBV capsids into nonsusceptible cells, circumventing the natural entry pathway. Successful infection was monitored by observing the emergence of the nuclear viral covalently closed circular DNA and the production of progeny virus and subviral particles. Lipid-mediated transfer initiated productive infection that was at least 100-fold more effective than infection of permissive cell cultures. High-dose capsid transfer showed that the uptake was not receptor limited and allowed the intracellular transport of capsids and genomes to be examined microscopically. The addition of inhibitors confirmed an entry pathway by fusion of the lipid with the plasma membrane. By indirect immune fluorescence and native fluorescence in situ hybridization, we followed the pathway of capsids and viral genomes in individual cells. We observed an active microtubule-dependent capsid transfer to the nucleus and a subsequent release of the viral genomes exclusively into the karyoplasm. Lipid-mediated transfer of viral capsids thus appears to allow efficient introduction of genetic information into target cells, facilitating studies of early infection events which are otherwise impeded by the small number of viruses entering the cell.

Capsid↗

PubMed2025

Exploring precision medicine by utilizing individual genetic information for the management of Alzheimer's disease.

Alzheimer's Disease (AD) represents a formidable challenge in neurology, characterized by progressive neurodegeneration and cognitive decline. Traditional therapeutic approaches have failed to deliver significant outcomes, underscoring the need for innovative paradigms such as precision medicine. The review explores integrating genomic, biomarker-driven, and individualized therapeutic strategies to tackle AD. It examines the role of key genetic factors, including APOE and MTHFR polymorphisms, in influencing disease susceptibility and treatment responses. Advances in biomarker technologies, such as blood-based and imaging biomarkers, are highlighted for their potential in early diagnosis and patient stratification. Additionally, the review underscores the importance of tailoring interventions across different stages of AD, incorporating lifestyle modifications and emerging tools like artificial intelligence & recent patented technologies. Precision medicine offers a transformative pathway, aiming to deliver personalized, effective care that addresses the complex and multifactorial nature of AD. The paradigm shift promises improved clinical outcomes and enhanced patient quality of life.

Humans↗

PubMed2004

Prostate cancer chemoprevention agent development: the National Cancer Institute, Division of Cancer Prevention portfolio.

PURPOSE: We describe the current National Cancer Institute chemoprevention agent development program and provide a summary of the intermediate end points used. MATERIALS AND METHODS: The National Cancer Institute is currently sponsoring a wide range of studies of promising chemoprevention agents in a variety of informative cohorts, eg high grade prostatic intraepithelial neoplasia, positive family history of cancer, increased prostate specific antigen with negative biopsies, prostate cancer followed expectantly, prostate cancer awaiting definitive therapy and the general population. The rationale for each agent under investigation is derived from epidemiological observations, prostate cancer treatment trials, secondary analyses of large cancer prevention studies, an understanding of cancer biology and prostate carcinogenesis, and/or experimental animal models. RESULTS: Carcinogenesis is a multistep process occurring over decades which is characterized by disruption of the normal regulatory pathways controlling cellular proliferation, programmed cell death and differentiation. Administration of agents to reverse, inhibit or slow this process of malignant transformation is known as chemoprevention. CONCLUSIONS: Chemoprevention represents a promising approach to reducing the morbidity and mortality of prostate cancer. A variety of agents are currently being studied in phase 2 clinical trials, some of which may warrant subsequent evaluation in phase 3 trials with definitive cancer end points. Two large phase 3 trials, the Prostate Cancer Prevention Trial and the Selenium and Vitamin E Cancer Prevention Trial, which are ongoing, are also sponsored by the National Cancer Institute.

Anticarcinogenic Agents↗

PubMed2004

A computational approach for ordering signal transduction pathway components from genomics and proteomics Data.

BACKGROUND: Signal transduction is one of the most important biological processes by which cells convert an external signal into a response. Novel computational approaches to mapping proteins onto signaling pathways are needed to fully take advantage of the rapid accumulation of genomic and proteomics information. However, despite their importance, research on signaling pathways reconstruction utilizing large-scale genomics and proteomics information has been limited. RESULTS: We have developed an approach for predicting the order of signaling pathway components, assuming all the components on the pathways are known. Our method is built on a score function that integrates protein-protein interaction data and microarray gene expression data. Compared to the individual datasets, either protein interactions or gene transcript abundance measurements, the integrated approach leads to better identification of the order of the pathway components. CONCLUSIONS: As demonstrated in our study on the yeast MAPK signaling pathways, the integration analysis of high-throughput genomics and proteomics data can be a powerful means to infer the order of pathway components, enabling the transformation from molecular data into knowledge of cellular mechanisms.

Computational Biology↗

PubMed1997

ladybird, a new component of the cardiogenic pathway in Drosophila required for diversification of heart precursors.

The embryonic heart precursors of Drosophila are arranged in a repeated pattern of segmental units. There is growing evidence that the development of individual elements of this pattern depends on both mesoderm intrinsic patterning information and inductive signals from the ectoderm. In this study, we demonstrate that two homeobox genes, ladybird early and ladybird late, are involved in the cardiogenic pathway in Drosophila. Their expression is specific to a subset of cardioblast and pericardial cell precursors and is critically dependent on mesodermal tinman function, epidermal Wingless signaling and the coordinate action of neurogenic genes. Negative regulation by hedgehog is required to restrict ladybird expression to two out of six cardioblasts in each hemisegment. Overexpression of ladybird causes a hyperplasia of heart precursors and alters the identity of even-skipped-positive pericardial cells. Loss of ladybird function leads to the opposite transformation, suggesting that ladybird participates in the determination of heart lineages and is required to specify the identities of subpopulations of heart cells. We find that both early Wingless signaling and ladybird-dependent late Wingless signaling are required for proper heart formation. Thus, we propose that ladybird plays a dual role in cardiogenesis: (i) during the early phase, it is involved in specification of a segmental subset of heart precursors as a component of the cardiogenic tinman-cascade and (ii) during the late phase, it is needed for maintaining wingless activity and thereby sustaining the heart pattern process. These events result in a diversification of heart cell identities within each segment.

Animals↗

PubMed1990

Mechanisms of positional signalling in the developing eye of Drosophila studied by ectopic expression of sevenless and rough.

In the developing eye of Drosophila cell fate is controlled by a cascade of inductive interactions. Little is known about how the specificity of positional signalling is achieved such that directly adjacent progenitor cells reproducibly choose distinct developmental pathways. The determination of the R7 photoreceptor in each ommatidium depends on the presence of the sevenless protein which acts as a receptor for positional information on the R7 precursor. The rough gene encodes a homeodomain protein that plays an instructive role in the determination of the R3 and R4 photoreceptor cells. The use of ectopic expression of sevenless and rough has provided insight into the mechanisms of positional signalling and the normal function of rough. Ubiquitous expression of sevenless does not alter cell fate suggesting that the inducing signal is both spatially and temporally controlled. Conversely, ectopic expression of rough in the R7 precursor causes a transformation of R7 cells into R1-6 type cells. This indicates that rough acts, similar to other homeobox genes, as a selector gene that determines the fate of single cells.

Animals↗

PubMed2005

Motor functions of the parietal lobe.

There is now general agreement that the posterior parietal cortex is part of the motor system. New data have confirmed its fundamental role in visuomotor transformations. Most interestingly, recent data showed that the inferior parietal lobule codes motor acts (such as grasping) in a specific way according to the action in which they are embedded. This particular motor organization appears to provide a neural mechanism for higher order cognitive motor functions, including understanding of intention. These functions, and peripersonal space representation, are represented in areas of the inferior parietal lobule, where visual information from both the dorsal and the ventral stream is integrated with motor information.

Animals↗

PubMed2003

Candidate chromosomal regions for genes involved in activation of alternative lengthening of telomeres in human immortal cell lines.

Either telomerase or alternative mechanisms known as alternative lengthening of telomeres (ALT) are activated in human immortal cells to maintain or lengthen their telomeres. To screen candidate chromosomes harboring gene(s) involved in activation of the telomere maintenance mechanisms that are repressed in normal, mortal cells and lost in immortal cells, we examined loss of heterozygosity (LOH) on the 22 autosomes and the X chromosome in 22 in vitro established human immortal cell lines consisting of 9 telomerase-positive cell lines and 13 ALT-positive cell lines. For detecting LOH, PCR analysis was performed with 66 polymorphic microsatellite markers from candidate genomic regions previously implicated for putative human senescence genes, telomerase repressor genes, or tumor suppressor genes. LOH involving chromosome 8 was observed at 25 of 62 (40%) informative loci in 8 of 13 (61%) ALT-positive cell lines. Particularly, when assayed with D8S339 adjacent to the Werner's syndrome gene, LOH was found in 6 of 12 (50%) informative ALT-positive cell lines. In contrast, no LOH on chromosome 8 was detected at 41 informative loci in any of 9 telomerase-positive cell lines. No other chromosomes showed high frequencies of LOH common in either ALT-positive or telomerase-positive cell lines. Although further LOH analysis with additional markers remains to define the specific region on chromosome 8, our results suggest that gene(s) involved in activation of the ALT pathway in human immortal cell lines may localize on chromosome 8.

Cell Line, Transformed↗