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Query: UMLS:C0004135 (ATM)
 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An immortalized cell line was established from a female ataxia telangiectasia (AT) patient by the transfection of primary skin fibroblasts with origin-defective SV40 DNA. The cell line was characterized by a hypodiploid chromosome constitution and radiation hypersensitivity. The established cell line was used as a recipient for microcell-mediated chromosome transfer. Among seven G418-resistant clones obtained by the fusion with microcells from mouse A9 cells carrying a pSV2neo-tagged normal human chromosome 11, three clones showed restoration of radiation resistance with concomitant gain of an extra intact chromosome 11, while the others contained no recognizable or deleted chromosome 11. The association of the presence of 11q14----qter region with the radioresistance suggests the presence of AT gene in this chromosomal region.
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PMID:Establishment of a novel immortalized cell line from ataxia telangiectasia fibroblasts and its use for the chromosomal assignment of radiosensitivity gene. 197 55

In order to identify the human chromosome which carries a mutated gene in cells from a patient with the hereditary disorder ataxia telangiectasia belonging to complementation group D (AT-D), we performed chromosome transfer experiments via microcell fusion. A single, pSV2neo-tagged chromosome, either 11 or 12, derived from normal human fibroblasts was introduced into AT-D cells by microcell fusion, and clones which were resistant to the antibiotic G418 were isolated. All 3 hybrid clones containing an additional copy number of chromosome 11 showed a restoration of the resistance of wild-type cells to killing by X-irradiation, whereas all 3 hybrid clones containing an additional copy number of chromosome 12 remained hyper-radiosensitive, like the parental AT cells. The results indicate that a defective gene of AT-D cells is also located on chromosome 11, since a genetic linkage analysis has previously suggested that a defective gene of its complementation group A is located on this chromosome.
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PMID:Restoration of radiation resistance in ataxia telangiectasia cells by the introduction of normal human chromosome 11. 215 85

Ataxia-telangiectasia (A-T) is a multisystem hereditary disease featuring neurodegeneration, immunodeficiency, extreme cancer proneness, chromosomal instability, and radiosensitivity. A-T is found in many ethnic groups, and is genetically heterogeneous: four complementation groups have been identified in A-T so far. Attempts to isolate the A-T gene are based in part on gene transfer experiments, using permanent A-T fibroblast lines, obtained by transformation with SV40. "Immortalization" of A-T primary diploid fibroblasts using SV40 is difficult, possibly because of the chromosomal instability of these cells. The number of currently available permanent A-T fibroblast lines is small, and not all of them have been assigned to specific complementation groups. Using the assay of X-ray induced inhibition of DNA synthesis, we have assigned the A-T strain AT22IJE to complementation group AB. Origin-defective SV40 was used to transfect these cells, and one transformant (AT22IJE-T), which survived crisis, was found to have the typical characteristics of permanent cell lines obtained in this way. "In-gel renaturation" analysis did not show any DNA amplification of high degree in AT22IJE-T. Cytogenetic analysis showed considerable chromosomal instability in the new cell line, and medium conditioned by these cells contained the clastogenic activity which is characteristic of the parental strain as well. Other parameters of the "cellular A-T phenotype" have also been retained in the immortalized cells: hypersensitivity to the lethal effects of X-rays and neocarzinostatin, as well as "radioresistant" DNA synthesis. However, the sensitivity of AT22IJE-T to both DNA-damaging agents is less pronounced than that of the parental cells. The capacity of the cells for uptake of foreign DNA was tested by introducing into them the plasmid pRSVneo, using three different transfection methods. Satisfactory frequency of G418-resistant transfectants (0.66%) was achieved using a protocol recently published by Chen and Okayama (Mol. Cell Biol., 7: 2745-2752, 1987), which was found to be superior to the traditional calcium phosphate transfection method and to the polybrene-based method.
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PMID:Cellular and molecular characteristics of an immortalized ataxia-telangiectasia (group AB) cell line. 253 4

We have evaluated the ability of immortalized human fibroblasts to recombine transfected plasmid DNA. A number of cell lines from normal individuals and from patients with DNA damage-processing defects were examined. Two plasmid recombination substrates were derived from pSV2neo and contained nonoverlapping deletions in the aminoglycoside phosphotransferase II gene. Intermolecular recombination was assessed by two methods after cotransfection. In a short-term, extrachromosomal recombination assay, low molecular weight DNA was extracted from the human cells 48 h after transfection, and recombinant plasmids were detected by transformation into appropriate indicator bacteria. In a long-term stable recombination assay the fibroblasts were cotransfected and G418-resistant colonies allowed to form. By the former assay all but two cultures were recombination-proficient, whereas all were recombination-proficient by the latter assay. The efficiency of transfection of human cells with plasmids appears to be a major variable affecting recombination. Recombination can be stimulated by uv irradiation of plasmid DNA prior to transfection. Cells from patients with Fanconi anemia, ataxia telangiectasia, and xeroderma pigmentosum complementation groups A, C, D, E, and G are not defective at intermolecular plasmid recombination.
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PMID:Intermolecular plasmid recombination in fibroblasts from humans with DNA damage-processing defects. 255 Sep 80

SV40-transformed ataxia-telangiectasia (AT) cells were transfected with a cosmid that contains a normal human DNA library and a selectable marker, the neo gene, which endows successfully transformed mammalian cells with resistance to the antibiotic G418. After a three-part selection protocol for G418 resistance and radioresistance, a cell line stably resistant to ionizing radiation was recovered. Cells from this line were irradiated with 50 Gy of X-rays and fused with non-transfected AT cells. Among the G418-resistant colonies recovered was one that was stably resistant to radiation. Resistance to ionizing radiation of both the primary transfectant line and its fusion derivative was intermediate between that of AT cells and normal cells, as assayed by colony-forming ability and measurement of radiation-induced G2 chromatid aberrations; both cell lines retained AT-like radioresistant DNA synthesis. These results suggest that, because radioresistance in the transfected cells was not as great as that in normal human cells, the two hallmarks of AT, radiosensitivity and radioresistant DNA synthesis, may still be the result of a single defective AT gene.
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PMID:Stable radioresistance in ataxia-telangiectasia cells containing DNA from normal human cells. 257 62

The AT1-R has been implicated in many cellular and physiological actions of angiotensin II (AII) in the brain. A retrovirus vector (LNSV) containing an AT1B-R antisense sequence (AT1B-AS) (termed LNSV-AT1B-AS) was constructed and used to determine the feasibility of using viral-mediated gene transfer to control AT1-Rs and AII actions in astroglial and neuronal cells in primary cultures from rat brain. Briefly, a 1.26-kb antisense sequence corresponding to nt -132 to +1128 of AT1-R cDNA was cloned into the LNSV vector, the vector was transfected into PA317 cells, and transfected cells were selected in G418. Incubation of brain cells with culture medium containing LNSV-AT1B-AS viral particles showed that AT1B-AS was integrated into the genome and transcribed in brain cells. This was associated with a significant decrease in AT1-Rs and in the AII-stimulated increase of c-fos mRNA, a measure of AT1-R function. These observations show that the AT1B-AS gene can be transferred into astroglial cells in culture by LNSV and that such a transfer inhibits AT1-Rs and the AII stimulation of cellular activities. In addition, the usefulness of this approach to study AII-dependent pathophysiology in primary neuronal cultures from brain, in particular, is established.
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PMID:Retrovirus-mediated transfer of an angiotensin type I receptor (AT1-R) antisense sequence decreases AT1-Rs and angiotensin II action in astroglial and neuronal cells in primary cultures from the brain. 786 53

The fibroblast cell line AT5BIVA, from ataxia telangiectasia complementation group D, was transfected with a neo gene providing G418 resistance for subsequent selections. The G418 resistant cell line was fused with gamma-irradiated Chinese hamster ovary cells and a radioresistant hybrid, atxbc, was isolated following an X-ray selection procedure. All the cellular defects characteristic of ataxia telangiectasia were corrected to some degree; atxbc cells: (i) were confirmed to be resistant to X-rays; (ii) had regained control over DNA synthesis after DNA damage, and (iii) could overcome the radiation-induced block in the G2 phase of the cell cycle. Repetitive element polymerase chain reaction amplification of integrated hamster DNA from primers to middle repetitive elements confirmed the presence of hamster-specific sequences, suggesting that the phenotype of the cells had been corrected by integration of a normal hamster gene rather than by a reversion event.
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PMID:Characterization of a hybrid hamster-human cell line complemented for the ataxia telangiectasia DNA repair defects. 794 20

Frequent allelic deletion at chromosome 11q22-q23.1 has been described in breast cancer and a number of other malignancies, suggesting putative tumour suppressor gene(s) within the approximately 8 Mb deleted region. In addition, we recently described another locus, at the 11q25-qter region, frequently deleted in breast cancer, suggesting additional tumour suppressor gene(s) in this approximately 2 Mb deleted region. An 11q YAC contig was accessed and three YACs, one containing the candidate gene ATM at 11q23.1, and two contiguous YACs (overlapping for approximately 400-600 kb) overlying most of the 11q25 deleted region, were retrofitted with a G418 resistance marker and transfected into murine A9 fibrosarcoma cells. Selected A9 transfectant clones (and control untransfected and 'irrelevant' alphoid YAC transfectant A9 clones) were assayed for in vivo tumorigenicity in athymic female Balb c-nu/nu mice. All the 11q YAC transfectant clones demonstrated significant tumour suppression compared to the control untransfected and 'irrelevant' YAC transfected A9 cells. These results define two discrete tumour suppressor loci on chromosome 11q by functional complementation, one to a approximately 1.2 Mb region on 11q23.1 (containing the ATM locus) and another to a approximately 400-600 kb subterminal region on 11q25-qter.
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PMID:11q23.1 and 11q25-qter YACs suppress tumour growth in vivo. 1002 21

Angiotensin II is well implicated in neointimal proliferation and the resulting restenosis, however, the mechanisms involved remain unclear. The type 2 angiotensin II (AT2) receptor, largely unexpressed in the adult vasculature, however, appears at significant levels after vascular injury. To investigate the specific contribution of AT2 receptor and the interplay of the angiotensin system to neointima, we engineered rat vascular smooth muscle cells (VSMCs) to express the AT2 receptor in a tetracycline-regulated system. Several VSMC clones resistant to both hygromycin and G418 were selected, many of which showed high, but regulatable levels of AT2R expression within 48 h of doxycycline (Dox) exposure. In untransfected VSMCs and stable transfectants with no AT2R induction, Ang II significantly increased the expression of matrix metalloproteinase 2 (MMP-2), which is linked to neointimal growth. However, induction of AT2R by Dox addition markedly decreased MMP-2 levels (P<0.01) and this downregulation was further promoted by CV-11974, a specific antagonist of AT1 receptor. In contrast, the PD123319 compound, which selectively curtails the AT2 receptor, reversed the inhibition caused by CV-11974. We conclude that Ang II enhances the MMP-2 expression via AT1R, and that enforces AT2R inhibited the same. These data confirm that AT2R functions to downregulate the effects elicited by Ang II + AT1R signaling and point to the role of MMP and extracellular matrix in vascular injury. The findings provide fresh experimental approaches to prevent or control restenosis through transduction of VSMCs expressing optimal levels of AT2R.
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PMID:Conditional expression of type 2 angiotensin II receptor in rat vascular smooth muscle cells reveals the interplay of the angiotensin system in matrix metalloproteinase 2 expression and vascular remodeling. 1951 42

A recent challenge for investigators studying the progressive neurological disease ataxia-telangiectasia (A-T) is to identify mutations whose effects might be alleviated by mutation-targeted therapies. We studied ATM mutations in eight families of Japanese A-T patients (JPAT) and were able to identify all 16 mutations. The probands were compound heterozygotes in seven families, and one (JPAT2) was homozygous for a frameshift mutation. All mutations--four frameshift, two nonsense, four large genomic deletions, and six affecting splicing--were novel except for c.748C>T found in family JPAT6 and c.2639-384A>G found in family JPAT11/12. Using an established lymphoblastoid cell line (LCL) of patient JPAT11, ATM protein was restored to levels approaching wild type by exposure to an antisense morpholino oligonucleotide designed to correct a pseudoexon splicing mutation. In addition, in an LCL from patient JPAT8/9, a heterozygous carrier of a nonsense mutation, ATM levels could also be partially restored by exposure to readthrough compounds (RTCs): an aminoglycoside, G418, and a novel small molecule identified in our laboratory, RTC13. Taken together, our results suggest that screening and functional characterization of the various sorts of mutations affecting the ATM gene can lead to better identification of A-T patients who are most likely to benefit from rapidly developing mutation-targeted therapeutic technologies.
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PMID:Functional characterization and targeted correction of ATM mutations identified in Japanese patients with ataxia-telangiectasia. 2200 93


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