Biomedical subjects

R L Margolis

Publications and source records attributed to R L Margolis.

At least 19 recordsLinked to original sources

PubMed2006

A novel trinucleotide repeat expansion at chromosome 3q26.2 identified by a CAG/CTG repeat expansion detection array.

CAG/CTG repeat expansions cause at least 12 different neurological disorders, and additional disorders of this type probably exist. Using the repeat expansion detection (RED) assay, we identified an expanded CAG/CTG repeat in a 50-year-old woman with an autosomal dominant syndrome with prominent progressive sensory neuropathy. The expansion could not be accounted for by any of the CAG/CTG repeats known to undergo expansion. To identify the locus of the expansion, we created a PCR array to assess the repeat length of all repeats of eight or more CAG or CTG triplets in the human genome. The expansion was localized to a repeat contained in an intron of a Genscan-predicted gene, 185 nt downstream of a predicted exon that is conserved through mouse. The closest experimentally verified gene in the region (TNIK, encoding a serine/threonine kinase) occurs approximately 63 Kb downstream from the repeat. The length of the expansion in the proband is 98 triplets. This repeat is not expanded in the proband's cousin (the only other affected family member for whom DNA is currently available) and no expansions were detected in a set of 230 patients with movement disorders of unknown cause. An expanded allele containing 58 triplets was detected in a single control individual, and no other expansions were detected in a set of 255 controls. The normal repeat length ranges from 5 to 30 triplets, with 8 triplets the most common allele. Our results suggest that this new repeat expansion is probably not the direct cause of the phenotype in the proband. Whether the repeat contributes to the patient's phenotype, or is associated with another phenotype, remains to be determined.

Alleles↗

PubMed2006

The association of CAG repeat length with clinical progression in Huntington disease.

OBJECTIVE: To determine whether the rate of clinical progression in Huntington disease (HD) is influenced by the size of the CAG expansion. METHODS: The dataset consisted of 3,402 examinations of 512 subjects seen through the Baltimore Huntington's Disease Center. Subjects were seen for a mean of 6.64 visits, with mean follow-up of 6.74 years. Subjects were administered the Quantified Neurological Examination, with its subsets the Motor Impairment and Chorea Scores, the Mini-Mental State Examination, and the HD Activities of Daily Living (ADL) Scale. RESULTS: In an analysis based on the Random Effects Model, CAG length was significantly associated with the rate of progression of all measures except chorea and ADL. There was a significant interaction term between CAG length and disease duration for all measures except chorea. Further graphical exploration of the data supported these linear models and suggested that subjects at the low end of the expanded CAG repeat range may experience a more benign late course. CONCLUSIONS: CAG repeat length has a small effect on rate of progression that may be clinically important over time. Individuals with the shortest expansions appear to have the best prognosis. These effects of the CAG length may be relevant in the analysis of clinical trials.

Baltimore↗

PubMed2005

The clinical and genetic spectrum of spinocerebellar ataxia 14.

Spinocerebellar ataxia 14 (SCA14) is associated with missense mutations in the protein kinase C gamma gene (PRKCG), rather than a nucleotide repeat expansion. In this large-scale study of PRKCG in patients with ataxia, two new missense mutations, an in-frame deletion, and a possible splice site mutation were found and can now be added to the four previously described missense mutations. The genotype/phenotype correlations in these families are described.

Adolescent↗

PubMed2005

A frameshift mutation in Disrupted in Schizophrenia 1 in an American family with schizophrenia and schizoaffective disorder.

In a large Scottish pedigree, a balanced translocation t(1;11)(q42.1;q14.3) segregates with major mental illness, including schizophrenia, bipolar disorder, and recurrent major depression. The translocation is predicted to result in the loss of the C-terminal region of the protein product of Disrupted In SChizophrenia 1 (DISC1), a gene located on 1q42.1. Since this initial discovery, DISC1 has been functionally implicated in several processes, including neurodevelopment. Based on the genetic and functional evidence that DISC1 may be associated with schizophrenia, we sequenced portions of DISC1 in 28 unrelated probands with schizophrenia and six unrelated probands with schizoaffective disorder, ascertained as part of a large sibpair study. We detected a 4 bp deletion at the extreme 3' end of exon 12 in a proband with schizophrenia. The mutation was also present in a sib with schizophrenia, a sib with schizoaffective disorder, and the unaffected father, while the mutation was not detected in 424 control individuals. The mutation is predicted to cause a frameshift and encode a truncated protein with nine abnormal C-terminal amino acids. The truncated transcript is detectable, but at a reduced level, in lymphoblastoid cell lines from three of four mutation carriers. These findings are consistent with the possibility that mutations in the DISC1 gene can increase the risk for schizophrenia and related disorders.

Cloning, Molecular↗

PubMed2005

Evidence of a common founder for SCA12 in the Indian population.

Spinocerebellar ataxia type 12 (SCA12) is an autosomal dominant cerebellar ataxia associated with the expansion of an unstable CAG repeat in the 5' region of the PPP2R2B gene on chromosome 5q31-5q32. We found that it accounts for approximately 16% (20/124) of all the autosomal dominant ataxia cases diagnosed in AIIMS, a major tertiary referral centre in North India. The length of the expanded allele in this population ranges from 51-69 CAG triplets. Interestingly, all the affected families belong to an endogamous population, which originated in the state of Haryana, India. We identified four novel SNPs and a dinucleotide marker spanning approximately 137 kb downstream of CAG repeat in the PPP2R2B gene. Analysis of 20 Indian SCA12 families and ethnically matched normal unrelated individuals revealed one haplotype to be significantly associated with the affected alleles (P= 0.000), clearly indicating the presence of a common founder for SCA12 in the Indian population. This haplotype was not shared by the American pedigree with SCA12. Therefore, the SCA12 expansion appears to have originated at least twice.

Alleles↗

PubMed2004

Onset and rate of striatal atrophy in preclinical Huntington disease.

BACKGROUND: Huntington disease (HD) is characterized by striatal atrophy that begins long before the onset of motor symptoms. OBJECTIVE: To determine when striatal atrophy begins, the extent and rate of atrophy before diagnosis of motor symptoms, and whether striatal atrophy can predict when symptom onset will occur. METHODS: Caudate and putamen volumes were measured on MRI scans of 19 preclinical subjects with the HD gene expansion who were very far (9 to 20 years) from estimated onset, and on serial scans from 17 preclinical subjects, six of whom were diagnosed with HD within 5 years after the initial scan. RESULTS: Striatal volumes were significantly smaller for the subjects who were very far from estimated onset than for age-matched control subjects. Statistical models fit to the longitudinal data suggest that rate of caudate atrophy becomes significant when subjects are approximately 11 years from estimated onset and rate of putamen atrophy becomes significant approximately 9 years prior to onset. In the six incident cases, caudate and putamen were approximately one-third to one-half of normal volume at diagnosis, and caudate volume alone was able to predict with 100% accuracy those subjects who would be diagnosed within 2 years of imaging. CONCLUSIONS: Striatal atrophy begins many years prior to diagnosable HD, and assessment of atrophy on MRI may be very useful in both predicting HD onset and in tracking progression in future therapeutic trials in preclinical subjects.

Adult↗

PubMed2004

Novel CAG/CTG repeat expansion mutations do not contribute to the genetic risk for most cases of bipolar disorder or schizophrenia.

The possible presence of anticipation in bipolar affective disorder and schizophrenia has led to the hypothesis that repeat expansion mutations could contribute to the genetic etiology of these diseases. Using the repeat expansion detection (RED) assay, we have systematically examined genomic DNA from 100 unrelated probands with schizophrenia and 68 unrelated probands with bipolar affective disorder for the presence of CAG/CTG repeat expansions. Our results show that 28% of the probands with schizophrenia and 30% of probands with bipolar disorder have a CAG/CTG repeat in the expanded range, but that each expansion could be explained by one of three nonpathogenic repeat expansions known to exist in the general population. We conclude that novel CAG/CTG repeat expansions are not a common genetic risk factor for bipolar disorder or schizophrenia.

Bipolar Disorder↗

PubMed2003

Huntington's disease--like 2 can present as chorea-acanthocytosis.

Three patients from a previously described family with autosomal dominant chorea-acanthocytosis were found to have the CTG trinucleotide repeat expansion mutation of the junctophilin-3 gene associated with Huntington's disease-like 2 (HDL2). One of six previously identified patients with HDL2 had acanthocytosis on peripheral blood smear, suggesting that HDL2 should be considered in the differential of chorea-acanthocytosis.

Acanthocytes↗

PubMed2003

Why is SCA12 different from other SCAs?

Spinocerebellar ataxia type 12 (SCA12), now described in European-American and Asian (Indian) pedigrees, is unique among the SCAs from clinical, pathological, and molecular perspectives. Clinically, the distinguishing feature is early and prominent action tremor with variability in other signs. Pathologically, brain MRIs also suggest variability, with prominent cortical as well as cerebellar atrophy. Genetically, SCA12 is caused by a CAG repeat expansion that does not encode polyglutamine; we speculate that the mutation may affect expression of the gene PPP2R2B, which encodes a brain-specific regulatory subunit of the protein phosphatase PP2A.

Alleles↗

PubMed2002

CAG/CTG repeat expansions at the Huntington's disease-like 2 locus are rare in Huntington's disease patients.

The authors report a large series of patients with Huntington disease (HD)-like phenotype without CAG repeat expansions in the IT15 gene that were screened for the newly identified CAG/CTG expansion in the gene encoding junctophilin-3. Normal alleles in controls had from 8 to 28 repeats. A single patient of North African origin with typical HD carried an allele with 50 uninterrupted repeats, representing approximately 2% of the non-IT15 HD patients tested. Therefore, further genetic heterogeneity is expected in HD.

Adolescent↗

PubMed2002

Trinucleotide repeats in 202 families with ataxia: a small expanded (CAG)n allele at the SCA17 locus.

BACKGROUND: Ten neurodegenerative disorders characterized by spinocerebellar ataxia (SCA) are known to be caused by trinucleotide repeat (TNR) expansions. However, in some instances the molecular diagnosis is considered indeterminate because of the overlap between normal and affected allele ranges. In addition, the mechanism that generates expanded alleles is not completely understood. OBJECTIVE: To examine the clinical and molecular characteristics of a large group of Portuguese and Brazilian families with ataxia to improve knowledge of the molecular diagnosis of SCA. PATIENTS AND METHODS: We have (1) assessed repeat sizes at all known TNR loci implicated in SCA; (2) determined frequency distributions of normal alleles and expansions; and (3) looked at genotype-phenotype correlations in 202 unrelated Portuguese and Brazilian patients with SCA. Molecular analysis of TNR expansions was performed using polymerase chain reaction amplification. RESULTS: Patients from 110 unrelated families with SCA showed TNR expansions at 1 of the loci studied. Dominantly transmitted cases had (CAG)(n) expansions at the Machado-Joseph disease gene (MJD1) (63%), at SCA2 (3%), the gene for dentatorubropallidoluysian atrophy (DRPLA) (2%), SCA6 (1%), or SCA7 (1%) loci, or (CTG)(n) expansions at the SCA8 (2%) gene, whereas (GAA)(n) expansions in the Freidreich ataxia gene (FRDA) were found in 64% of families with recessive ataxia. Isolated patients also had TNR expansions at the MJD1 (6%), SCA8 (6%), or FRDA (8%) genes; in addition, an expanded allele at the TATA-binding protein gene (TBP), with 43 CAGs, was present in a patient with ataxia and mental deterioration. Associations between frequencies of SCA2 and SCA6 and a frequency of large normal alleles were found in Portuguese and Brazilian individuals, respectively. Interestingly, no association between the frequencies of DRPLA and large normal alleles was found in the Portuguese group. CONCLUSIONS: Our results show that (1) a significant number of isolated cases of ataxia are due to TNR expansions; (2) expanded DRPLA alleles in Portuguese families may have evolved from an ancestral haplotype; and (3) small (CAG)(n) expansions at the TBP gene may cause SCA17.

Adenine↗

PubMed2001

Neither p21WAF1 nor 14-3-3sigma prevents G2 progression to mitotic catastrophe in human colon carcinoma cells after DNA damage, but p21WAF1 induces stable G1 arrest in resulting tetraploid cells.

p21WAF1 and 14-3-3sigma, which are both transcriptional products of p53, have been reported to play a role in the G2 DNA damage checkpoint in mammalian cells. Human colon carcinoma cells, isogenic except for the presence or absence of either p21WAF1 or 14-3-3sigma (T. A. Chan et al., Genes Dev., 14: 1584-1588, 2000), are useful models for analysis of the role of these proteins in checkpoint control. Here, we have examined mitotic behavior within a single cell cycle after DNA damage in these cell lines. Our results show that p21WAF1, but not 14-3-3sigma, imposes a significant G2 delay after DNA damage. After G2 delay, we found that all isogenic cells, including those competent for both p21WAF1 and 14-3-3sigma, adapt to the DNA damage checkpoint and progress into mitosis, where they undergo incomplete chromosome segregation and reenter G1 with a tetraploid DNA content. Strikingly, our results show that p21WAF1, but not 14-3-3sigma, activates a checkpoint in response to DNA damage that prevents continued cycling of the tetraploid cells that result from a mitotic catastrophe characterized by failure to complete cell division. These results demonstrate that a tetraploid DNA content is not a reliable criterion to establish that arrest occurs in G2. Also, the DNA damage checkpoint mediated by p53-dependent induction of p21WAF1 assures neither G2 arrest nor DNA repair sufficient to enable accurate chromosome segregation in human colon carcinoma cells. We conclude that p21WAF1, but not 14-3-3sigma, has a unique role in the induction of G1 arrest in tetraploid cells that results from mitotic catastrophe after DNA damage.

14-3-3 Proteins↗

PubMed2001

Familial influence on age of onset among siblings with Huntington disease.

In order to provide data relevant to a search for modifying genes for age of onset in Huntington disease, we examined the relationship between CAG number and age of onset in a total of 370 individuals from 165 siblingships, in two cohorts of siblings with Huntington disease: an American group of 144 individuals from 64 siblingships, and a Canadian population of 255 individuals from 113 siblingships. Using a logarithmic model to regress the age of onset on the number of CAG triplets, we found that CAG number alone accounted for 65%-71% of the variance in age of onset. The siblingship an individual belonged to accounted for 11%-19% of additional variance. This adds to the previous evidence that there are familial modifiers of the age of onset, independent of the CAG number. Such modifiers may consist of additional genes, which could be the target of a linkage study. A linkage study is feasible with the cooperation of a number of major centers and may be made more efficient by concentrating on sibling pairs that are highly discordant for age of onset.

Age of Onset↗

PubMed2001

Tubulin detyrosination is a frequent occurrence in breast cancers of poor prognosis.

Tubulin, the dimeric subunit of microtubules, is a major cell protein that is centrally involved in cell division. Tubulin is subject to specific enzymatic posttranslational modifications including cyclic tyrosine removal and addition at the COOH terminus of the alpha-subunit. Tubulin is normally extensively tyrosinated in cycling cells. However, we have previously shown that detyrosinated tubulin accumulates in cancer cells during tumor progression in nude mice. Tubulin detyrosination, resulting from suppression of tubulin tyrosine ligase and the resulting unbalanced activity of tubulin-carboxypeptidase, apparently represents a strong selective advantage for cancer cells. We have now analyzed the occurrence and significance of tubulin detyrosination in human breast tumors. We studied a total of 134 breast cancer tumors from patients with or without known complications over a follow-up period of 31 +/- 10 months. The mean age of the patients at the time of diagnosis was 57 years. For each patient, detailed data concerning the histology and extension of the tumor were available. Tumor cells containing detyrosinated tubulin were visualized by immunohistochemical staining of paraffin-embedded tissue sections. Cancer cells with detyrosinated tubulin were observed in 53% of the tumors and were predominant in 19.4% of the tumors. Tubulin detyrosination correlated to a high degree of significance (P < 0.001) with a high Scarf-Bloom-Richardson (SBR) grade, a known marker of tumor aggressiveness. Among SBR grade 1 tumors, 3.8% were strongly positive for tubulin detyrosination compared with 65.4% of the SBR grade 3 tumors. The SBR component showing the strongest correlation with tubulin detyrosination was the mitotic score. In the entire patient population, neither the SBR grade nor the detyrosination index had significant prognostic value (P = 0.11, P = 0.27, respectively), whereas a combined index was significantly correlated with the clinical outcome (P = 0.02). A preliminary subgroup analysis indicated that tubulin detyrosination may define high- and low- risk groups in breast cancer tumors with an SBR grade of 2. Our study shows that tubulin detyrosination is a frequent occurrence in breast cancer, easy to detect, and linked to tumor aggressiveness.

Adult↗

PubMed2001

Mammalian mad2 and bub1/bubR1 recognize distinct spindle-attachment and kinetochore-tension checkpoints.

Metaphase checkpoint controls sense abnormalities of chromosome alignment during mitosis and prevent progression to anaphase until proper alignment has been attained. A number of proteins, including mad2, bub1, and bubR1, have been implicated in the metaphase checkpoint control in mammalian cells. Metaphase checkpoints have been shown, in various systems, to read loss of either spindle tension or microtubule attachment at the kinetochore. Characteristically, HeLa cells arrest in metaphase in response to low levels of microtubule inhibitors that leave an intact spindle and a metaphase plate. Here we show that the arrest induced by nanomolar vinblastine correlates with loss of tension at the kinetochore, and that in response the checkpoint proteins bub1 and bubR1 are recruited to the kinetochore but mad2 is not. mad2 remains competent to respond and is recruited at higher drug doses that disrupt spindle association with the kinetochores. Further, although mad2 forms a complex with cdc20, it does not associate with bub1 or bubR1. We conclude that mammalian bub1/bubR1 and mad2 operate as elements of distinct pathways sensing tension and attachment, respectively.

Blotting, Western↗

PubMed2001

SCA-12: Tremor with cerebellar and cortical atrophy is associated with a CAG repeat expansion.

OBJECTIVE: To characterize the clinical and neuroradiologic features of a new spinocerebellar ataxia, SCA-12, in the index family. BACKGROUND: The authors recently linked SCA-12 to a novel CAG repeat expansion on chromosome 5q31-33 that is located within the 5' region of PPP2R2B, a gene encoding a brain-specific regulatory subunit of protein phosphatase 2A. METHODS: Neurologic features of the proband and nine symptomatic relatives in the first SCA-12 family were compiled and, in some individuals, related to changes found on brain MRI or CT. RESULTS: SCA-12 typically presented in the 4th decade of life with action tremor of the head or arms (present in 10/10 of the affected individuals). Hyperreflexia (8/10) was a common feature, and cerebellar signs (8/10), including ataxia, dysmetria, and dysarthria, developed gradually but were less prominent and disabling than cerebellar dysfunction in other SCA. Subtle parkinsonian features (9/10) and dementia (2/10) were observed in later stages of SCA-12, and psychiatric symptoms, including depression, anxiety, or delusions, were present in some affected family members (4/10). Two individuals studied had nondisabling neurologic signs neonatally, including nystagmus and lower extremity dystonia. Brain images of affected individuals revealed cerebral and cerebellar atrophy. CONCLUSIONS: SCA-12 is a slowly progressive, autosomal dominant, neurodegenerative disorder that differs from other SCA in that it typically presents with action tremor in patients in their mid 30s and usually includes hyperreflexia and subtle parkinsonian signs. Cerebellar dysfunction, including gait ataxia, is relatively nondisabling, and cognitive or psychiatric disorders may occur. Neuroradiologic studies reveal atrophy of the cerebellum and cerebral cortex.

Brain↗

PubMed2001

The Gln-Ala repeat transcriptional activator CA150 interacts with huntingtin: neuropathologic and genetic evidence for a role in Huntington's disease pathogenesis.

Huntington's disease (HD) is a neurodegenerative disease caused by polyglutamine expansion in the protein huntingtin (htt). Pathogenesis in HD appears to involve the formation of ubiquitinated neuronal intranuclear inclusions containing N-terminal mutated htt, abnormal protein interactions, and the aggregate sequestration of a variety of proteins (noticeably, transcription factors). To identify novel htt-interacting proteins in a simple model system, we used a yeast two-hybrid screen with a Caenorhabditis elegans activation domain library. We found a predicted WW domain protein (ZK1127.9) that interacts with N-terminal fragments of htt in two-hybrid tests. A human homologue of ZK1127.9 is CA150, a transcriptional coactivator with a N-terminal insertion that contains an imperfect (Gln-Ala)(38) tract encoded by a polymorphic repeat DNA. CA150 interacted in vitro with full-length htt from lymphoblastoid cells. The expression of CA150, measured immunohistochemically, was markedly increased in human HD brain tissue compared with normal age-matched human brain tissue, and CA150 showed aggregate formation with partial colocalization to ubiquitin-positive aggregates. In 432 HD patients, the CA150 repeat length explains a small, but statistically significant, amount of the variability in the onset age. Our data suggest that abnormal expression of CA150, mediated by interaction with polyglutamine-expanded htt, may alter transcription and have a role in HD pathogenesis.

Age of Onset↗

PubMed2001

A disorder similar to Huntington's disease is associated with a novel CAG repeat expansion.

Huntington's disease (HD) is an autosomal dominant disorder characterized by abnormalities of movement, cognition, and emotion and selective atrophy of the striatum and cerebral cortex. While the etiology of HD is known to be a CAG trinucleotide repeat expansion, the pathways by which this mutation causes HD pathology remain unclear. We now report a large pedigree with an autosomal dominant disorder that is clinically similar to HD and that arises from a different CAG expansion mutation. The disorder is characterized by onset in the fourth decade, involuntary movements and abnormalities of voluntary movement, psychiatric symptoms, weight loss, dementia, and a relentless course with death about 20 years after disease onset. Brain magnetic resonance imaging scans and an autopsy revealed marked striatal atrophy and moderate cortical atrophy, with striatal neurodegeneration in a dorsal to ventral gradient and occasional intranuclear inclusions. All tested affected individuals, and no tested unaffecteds, have a CAG trinucleotide repeat expansion of 50 to 60 triplets, as determined by the repeat expansion detection assay. Tests for the HD expansion, for all other known CAG expansion mutations, and for linkage to chromosomes 20p and 4p were negative, indicating that this mutation is novel. Cloning the causative CAG expansion mutation for this new disease, which we have termed Huntington's disease-like 2, may yield valuable insight into the pathogenesis of HD and related disorders.

Adult↗