Biomedical subjects

G Rotman

Publications and source records attributed to G Rotman.

At least 19 recordsLinked to original sources

PubMed1999

ATM: a mediator of multiple responses to genotoxic stress.

The ATM protein kinase is the product of the gene responsible for the pleiotropic recessive disorder ataxia-telangiectasia. ATM-deficient cells show enhanced sensitivity and greatly reduced responses to genotoxic agents that generate DNA double strand breaks (DSBs), such as ionizing radiation and radiomimetic chemicals, but exhibit normal responses to DNA adducts and base modifications induced by other agents. Therefore, DSBs are most likely the predominant signal for the activation of ATM-mediated pathways. Identification of the ATM gene triggered extensive research aimed at elucidating the numerous functions of its large multifaceted protein product. While ATM has both nuclear and cytoplasmic functions, this review will focus on its roles in the nucleus where it plays a central role in the very early stages of damage detection and serves as a master controller of cellular responses to DSBs. By activating key regulators of multiple signal transduction pathways, ATM mediates the efficient induction of a signaling network responsible for repair of the damage, and for cellular recovery and survival.

Animals↗

PubMed1998

Selective loss of dopaminergic nigro-striatal neurons in brains of Atm-deficient mice.

Ataxia-telangiectasia (AT) is a human disease caused by mutations in the ATM gene. The neural phenotype of AT includes progressive cerebellar neurodegeneration, which results in ataxia and eventual motor dysfunction. Surprisingly, mice in which the Atm gene has been inactivated lack distinct behavioral ataxia or pronounced cerebellar degeneration, the hallmarks of the human disease. To determine whether lack of the Atm protein can nonetheless lead to structural abnormalities in the brain, we compared brains from male Atm-deficient mice with male, age-matched controls. Atm-deficient mice exhibited severe degeneration of tyrosine hydroxylase-positive, dopaminergic nigro-striatal neurons, and their terminals in the striatum. This cell loss was accompanied by a large reduction in immunoreactivity for the dopamine transporter in the striatum. A reduction in dopaminergic neurons also was evident in the ventral tegmental area. This effect was selective in that the noradrenergic nucleus locus coeruleus was normal in these mice. Behaviorally, Atm-deficient mice expressed locomotor abnormalities manifested as stride-length asymmetry, which could be corrected by peripheral application of the dopaminergic precursor L-dopa. In addition, these mice were hypersensitive to the dopamine releasing drug D-amphetamine. These results indicate that ATM deficiency can severely affect dopaminergic neurons in the central nervous system and suggest possible strategies for treating this aspect of the disease.

Animals↗

PubMed1998

ATM: from gene to function.

The identification of ATM , the gene responsible for the pleiotropic recessive disease ataxia telangiectasia, has initiated extensive research to determine the functions of its multifaceted protein product. The ATM protein belongs to a family of protein kinases that share similarities at their C-terminal region with the catalytic domain of phosphatidylinositol 3-kinases. Studies with ataxia telangiectasia (A-T) cells and Atm-deficient mice have shown that ATM is a key regulator of multiple signaling cascades which respond to DNA strand breaks induced by damaging agents or by normal processes, such as meiotic or V(D)J recombination. These responses involve the activation of cell cycle checkpoints, DNA repair and apoptosis. Other roles outside the cell nucleus might be carried out by the cytoplasmic fraction of ATM. In addition, ATM appears to function as a 'caretaker', suppressing tumorigenesis in specific T cell lineages.

Animals↗

PubMed1997

Ataxia-telangiectasia: structural diversity of untranslated sequences suggests complex post-transcriptional regulation of ATM gene expression.

Mutations in the ATM gene are responsible for the multisystem disorder ataxia-telangiectasia, characterized by neurodegeneration, immune deficiency and cancer predisposition. While no alternative splicing was identified within the coding region, the first four exons of the ATM gene, which fall within the 5'untranslated region (UTR), undergo extensive alternative splicing. We identified 12 different 5'UTRs that show considerable diversity in length and sequence contents. These mRNA leaders, which range from 150 to 884 nucleotides (nt), are expected to form variable secondary structures and contain different numbers of AUG codons. The longest 5'UTR contains a total of 18 AUGs upstream of the translation start site. The 3'UTR of 3590 nt is contained within a single 3'exon. Alternative polyadenylation results in 3'UTRs of varying lengths. These structural features suggest that ATM expression might be subject to complex post-transcriptional regulation, enabling rapid modulation of ATM protein level in response to environmental stimuli or alterations in cellular physiological states.

Ataxia Telangiectasia↗

PubMed1997

Ataxia-telangiectasia: is ATM a sensor of oxidative damage and stress?

Ataxia-telangiectasia (A-T) is a pleiotropic recessive disorder characterized by cerebellar ataxia, immunodeficiency, specific developmental defects, profound predisposition to cancer and acute radiosensitivity. Functional inactivation of a single gene product, ATM, accounts for this compound phenotype. We suggest that ATM acts as a sensor of reactive oxygen species and/or oxidative damage of cellular macromolecules, including DNA. In turn, ATM induces signalling through multiple pathways, thereby coordinating acute phase stress responses with cell cycle checkpoint control and repair of oxidative damage. Absence of ATM is proposed to limit the repair of insidious oxidative damage that can occur under normal physiological conditions, ultimately leading to apoptosis of particularly sensitive cells, such as neurons and thymocytes.

Apoptosis↗

PubMed1997

Ataxia-telangiectasia locus: sequence analysis of 184 kb of human genomic DNA containing the entire ATM gene.

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder involving cerebellar degeneration, immunodeficiency, chromosomal instability, radiosensitivity, and cancer predisposition. The genomic organization of the A-T gene, designated ATM, was established recently. To date, more than 100 A-T-associated mutations have been reported in the ATM gene that do not support the existence of one or several mutational hotspots. To allow genotype/phenotype correlations it will be important to find additional ATM mutations. The nature and location of the mutations will also provide insights into the molecular processes that underly the disease. To facilitate the search for ATM mutations and to establish the basis for the identification of transcriptional regulatory elements, we have sequenced and report here 184,490 bp of genomic sequence from the human 11q22-23 chromosomal region containing the entire ATM gene, spanning 146 kb, and 10 kb of the 5'-region of an adjacent gene named E14/NPAT. The latter shares a bidirectional promoter with ATM and is transcribed in the opposite direction. The entire region is transcribed to approximately 85% and translated to 5%. Genome-wide repeats were found to constitute 37.2%, with LINE (17.1%) and Alu (14.6%) being the main repetitive elements. The high representation of LINE repeats is attributable to the presence of three full-length LINE-1s, inserted in the same orientation in introns 18 and 63 as well as downstream of the ATM gene. Homology searches suggest that ATM exon 2 could have derived from a mammalian interspersed repeat (MIR). Promoter recognition algorithms identified divergent promoter elements within the CpG island, which lies between the ATM and E14/NPAT genes, and provide evidence for a putative second ATM promoter located within intron 3, immediately upstream of the first coding exon. The low G+C level (38.1%) of the ATM locus is reflected in a strongly biased codon and amino acid usage of the gene.

Ataxia Telangiectasia↗

PubMed1997

The ATM gene and protein: possible roles in genome surveillance, checkpoint controls and cellular defence against oxidative stress.

The autosomal recessive disorder ataxia-telangiectasia (AT) is highly pleiotropic. It is characterized by gradual loss of Purkinje cells in the cerebellum, leading to progressive neuromotor deterioration, immunodeficiency, developmental defects in specific tissues, profound predisposition to malignancy and acute sensitivity to ionizing radiation. AT cells show chromosomal instability, premature senesence, radiosensitivity and defects in cell cycle checkpoints activated by ionizing radiation. Several radiation induced pathways that regulate the cell cycle seem to be defective in AT cells, at least one of which is mediated by TP53. Extensive characterization of the cellular defects of AT cells, together with the recent isolation of the ATM gene, has provided some insight into the possible physiological roles of the ATM protein. Several lines of evidence, including the nature of the agents that elicit the hypersensitivity of AT cells, point to the possibility of a defect in the response to damage induced by oxidative stress, which affects various cellular macromolecules. The ATM protein might have a role in activating defence mechanisms against oxidative stress. This hypothesis broadens the previous concept of the AT defect and explains several aspects of the AT phenotype that cannot be accounted for by defective processing of DNA damage.

Ataxia Telangiectasia↗

PubMed1996

Identification and chromosomal localization of Atm, the mouse homolog of the ataxia-telangiectasia gene.

Atm, the mouse homolog of the human ATM gene defective in ataxia-telangiectasia (A-T), has been identified. The entire coding sequence of the Atm transcript was cloned and found to contain an open reading frame encoding a protein of 3066 amino acids with 84% overall identity and 91% similarity to the human ATM protein. Variable levels of expression of Atm were observed in different tissues. Fluorescence in situ hybridization and linkage analysis located the Atm gene on mouse chromosome 9, band 9C, in a region homologous to the ATM region on human chromosome 11q22-q23.

Amino Acid Sequence↗

PubMed1996

A human gene (DDX10) encoding a putative DEAD-box RNA helicase at 11q22-q23.

A human gene encoding a putative RNA helicase, designated DDX10, was identified 400 kb telomeric to the ataxia-telangiectasia gene at chromosome 11q22-q23. The predicted amino acid sequence shows very high similarity to a subgroup of DEAD-box RNA helicases involved in ribosome biogenesis. This novel gene encodes a 3.2-kb transcript in a variety of human tissues. A processed pseudogene of DDX10 was detected at chromosome 9q21-q22. We observed a rare trinucleotide repeat length polymorphism within the coding sequence of DDX10.

Amino Acid Sequence↗

PubMed1996

Genomic Organization of the ATM gene.

The ATM gene was recently identified and found to be responsible for the genetic disorder ataxiatelgiectasia. The major ATM transcript is 13 kb. Using long-distance PCR, we determined the genomic structure of this gene and identified all of its exon-intron boundaries. The ATM gene spans approximately 150 kb of genomic DNA and consists of 66 exons. The initiation codon falls within exon 4. The last exon is 3.8 kb and contains the stop codon and a 3'-untranslated region of about 3600 nucleotides.

Ataxia Telangiectasia↗

PubMed1996

Ataxia-telangiectasia and the ATM gene: linking neurodegeneration, immunodeficiency, and cancer to cell cycle checkpoints.

Defects in regulation of the cellular life cycle may lead to premature cellular death or malignant transformation. Most of the proteins known to be involved in these processes are mediators of mitogenic signals or components of the cell cycle machinery. It has recently become evident, however, that systems responsible for ensuring genome stability and integrity are no less important in maintaining the normal life cycle of the cell. These systems include DNA repair enzymes and a recently emerging group of proteins that alert growth regulating mechanisms to the presence of DNA damage. These signals slow down the cell cycle while DNA repair ensues. Ataxia telangiectasia (A-T) is a genetic disorder whose clinical and cellular phenotype points to a defect in such a signaling system. A-T is characterized by neurodegeneration, immunodeficiency, radiosensitivity, cancer predisposition, and defective cell cycle checkpoints. The responsible gene, ATM, was recently cloned and sequenced. ATM encodes a large protein with a region highly similar to the catalytic domain of PI 3-kinases. The ATM protein is similar to a group of proteins in various organisms which are directly involved in the cell cycle response to DNA damage. It is expected to be part of a protein complex that responds to a specific type of DNA strand break by conveying a regulatory signal to other proteins. Interestingly, the immune and nervous systems, which differ markedly in their proliferation rates, are particularly sensitive to the absence of ATM function. The identification of the ATM gene highlights the growing importance of signal transduction initiated in the nucleus rather than in the external environment, for normal cellular growth.

Animals↗

PubMed1996

Predominance of null mutations in ataxia-telangiectasia.

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder involving cerebellar degeneration, immunodeficiency, chromosomal instability, radiosensitivity and cancer predisposition. The responsible gene, ATM, was recently identified by positional cloning and found to encode a putative 350 kDa protein with a Pl 3-kinase-like domain, presumably involved in mediating cell cycle arrest in response to radiation-induced DNA damage. The nature and location of A-T mutations should provide insight into the function of the ATM protein and the molecular basis of this pleiotropic disease. Of 44 A-T mutations identified by us to date, 39 (89%) are expected to inactivate the ATM protein by truncating it, by abolishing correct initiation or termination of translation, or by deleting large segments. Additional mutations are four smaller in-frame deletions and insertions, and one substitution of a highly conserved amino acid at the Pl 3-kinase domain. The emerging profile of mutations causing A-T is thus dominated by those expected to completely inactivate the ATM protein. ATM mutations with milder effects may result in phenotypes related, but not identical, to A-T.

Amino Acid Sequence↗

PubMed1995

A single ataxia telangiectasia gene with a product similar to PI-3 kinase.

A gene, ATM, that is mutated in the autosomal recessive disorder ataxia telangiectasia (AT) was identified by positional cloning on chromosome 11q22-23. AT is characterized by cerebellar degeneration, immunodeficiency, chromosomal instability, cancer predisposition, radiation sensitivity, and cell cycle abnormalities. The disease is genetically heterogeneous, with four complementation groups that have been suspected to represent different genes. ATM, which has a transcript of 12 kilobases, was found to be mutated in AT patients from all complementation groups, indicating that it is probably the sole gene responsible for this disorder. A partial ATM complementary DNA clone of 5.9 kilobases encoded a putative protein that is similar to several yeast and mammalian phosphatidylinositol-3' kinases that are involved in mitogenic signal transduction, meiotic recombination, and cell cycle control. The discovery of ATM should enhance understanding of AT and related syndromes and may allow the identification of AT heterozygotes, who are at increased risk of cancer.

Amino Acid Sequence↗

PubMed1995

A high-density microsatellite map of the ataxia-telangiectasia locus.

The locus of the autosomal recessive disorder ataxia-telangiectasia (A-T) has been assigned by linkage analysis with biallelic markers to a 4-Mb interval on chromosome 11q22-23, between GRIA4 and D11S1897. We have undertaken to saturate the A-T region with highly polymorphic microsatellite markers. To this end, we have identified seven new polymorphic CA-repeats in this region, and have mapped to it five new markers generated by Genethon and the Cooperative Human Linkage Center. These markers are in addition to 12 others that we have previously mapped or generated at the A-T locus. All 24 markers have been integrated into a high-density microsatellite map spanning some 6 Mb DNA. This map, which contains the A-T locus and flanking sequences, allows the construction of extensive, highly informative haplotypes.

Ataxia Telangiectasia↗

PubMed1995

Rapid identification of polymorphic CA-repeats in YAC clones.

Positional cloning of rare disease genes depends on the availability of highly polymorphic markers near the disease loci. The most abundant class of polymorphic markers in the human genome is CA-repeats. We have developed a strategy for the rapid isolation of highly polymorphic CA-repeats from YAC clones. Total DNA of yeast clones containing partly overlapping YACs is digested with frequent cutter restriction enzymes, blotted and hybridized with a poly(CA/GT) probe under high stringency conditions that enable preferential detection of long CA-repeats. The repeats detected in this way are isolated by PCR using vectorette linkers, sequenced, and appropriate flanking markers are constructed for genotyping. All of the CA-repeats identified using this approach were highly polymorphic. This simple and rapid approach should allow the development of highly polymorphic markers at any genomic region cloned in YACs.

Blotting, Southern↗

PubMed1995

The complete sequence of the coding region of the ATM gene reveals similarity to cell cycle regulators in different species.

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder involving cerebellar degeneration, immunodeficiency radiation sensitivity, and cancer predisposition. A-T heterozygotes are moderately cancer prone. The A-T gene, designated ATM, was recently identified in our laboratory by positional cloning, and a partial cDNA clone was found to encode a polypeptide with a PI-3 kinase domain. We report here the molecular cloning of a cDNA contig spanning the complete open reading frame of the ATM gene. The predicted protein of 3056 amino acids shows significant sequence similarities to several large proteins in yeast, Drosophila and mammals, all of which share the PI-3 kinase domain. Many of these proteins are involved in the detection of DNA damage and the control of cell cycle progression. Mutations in their genes confer a variety of phenotypes with features similar to those observed in human A-T cells. The complete sequence of the ATM gene product provides useful clues to the function of this protein, and furthers understanding of the pleiotropic nature of the A-T mutations.

Amino Acid Sequence↗

PubMed1994

A YAC contig spanning the ataxia-telangiectasia locus (groups A and C) at 11q22-q23.

Ataxia-telangiectasia (A-T) is an autosomal recessive disease involving cerebellar degeneration, immunodeficiency, cancer predisposition, chromosomal instability and radiosensitivity. A-T is heterogeneous, and the majority of A-T cases are associated with two complementation groups, A and C. The ATA and ATC loci are closely linked at chromosome 11q22-q23. Recombination mapping and linkage disequilibrium analysis have confined both loci between the markers D11S1817 and D11S927, spaced approximately 3.5 Mb apart. Isolation in yeast artificial chromosomes of the genomic segment defined by these loci is essential to identify the gene or genes containing the ATA and ATC mutations. A YAC contig spanning 4.5 Mb, which includes the D11S1817-D11S927 interval, was constructed using two whole genome libraries (ICRF and St. Louis), and a chromosome 11-specific library. Construction of this contig was expedited by prior generation of a region-specific ICRF sublibrary using Alu-PCR products derived from a radiation hybrid. The contig was expanded further by screening the libraries with Alu-PCR products derived from YAC clones and with STSs from YAC ends. YAC clones were aligned by fingerprinting with moderately repetitive probes.

Ataxia Telangiectasia↗

PubMed1994

Physical localization of microsatellite markers at the ataxia-telangiectasia locus at 11q22-q23.

The autosomal recessive disorder ataxia-telangiectasia (A-T) is genetically heterogeneous, with four complementation groups. The genes for the two major groups (ATA and ATC) have been mapped to 11q22-q23. Genetic analysis of the disease has been conducted to date using biallelic polymorphisms. We have physically mapped to this region eight new microsatellite markers that were generated by three laboratories that construct whole-genome linkage maps. These markers should be valuable for refined localization and positional cloning of the A-T genes and for diagnostic purposes. The results demonstrate the value of integrating genetic and physical maps generated by different laboratories.

Ataxia Telangiectasia↗