RESUMEN
In the face of a growing global burden of resistance to existing antibiotics, a combination of scientific and economic challenges has posed significant barriers to the development of novel antibacterials over the past few decades. Yet the bottlenecks at each stage of the pharmaceutical value chain-from discovery to post-marketing-present opportunities to reengineer an innovation pipeline that has fallen short. The upstream hurdles to lead identification and optimization may be eased with greater multi-sectoral collaboration, a growing array of alternatives to high-throughput screening, and the application of open source approaches. Product development partnerships and South-South innovation platforms have shown promise in bolstering the R&D efforts to tackle neglected diseases. Strategies that delink product sales from the firms' return on investment can help ensure that the twin goals of innovation and access are met. To effect these changes, both public and private sector stakeholders must show greater commitment to an R&D agenda that will address this problem, not only for industrialized countries but also globally.
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Antibacterianos/uso terapéutico , Industria Farmacéutica/economía , Farmacorresistencia Bacteriana , Pandemias/prevención & control , Asociación entre el Sector Público-Privado/economía , Antibacterianos/síntesis química , Bacterias/patogenicidad , Infecciones Bacterianas/tratamiento farmacológico , Infecciones Bacterianas/microbiología , Descubrimiento de Drogas , Industria Farmacéutica/organización & administración , Ensayos Analíticos de Alto Rendimiento , Humanos , Internacionalidad , Inversiones en Salud/economía , Enfermedades Desatendidas/tratamiento farmacológicoRESUMEN
The genetic basis of bipolar disorder (BPD) and schizophrenia (SCZ) has been established through numerous clinical and molecular studies. Although often considered separate nosological entities, evidence now suggests that the two syndromes may share some genetic liability. Recent studies have used a composite phenotype (psychosis) that includes BPD, SCZ, psychosis not otherwise specified, and schizoaffective disorder, to identify shared susceptibility loci. Several chromosomal regions are reported to be shared between these syndromes (18p, 6q, 10p, 13q, 22q). As a part of our endeavor to scan these regions, we report a positive linkage and association finding at 18p11.2 for psychosis. Two-point linkage analysis performed on a series of 52 multiplex pedigrees with 23 polymorphic markers yielded a LOD score of 2.02 at D18S37. An independent set of 159 parent offspring trios was used to confirm this suggestive finding. The TDT analysis yielded support for association between the marker D18S453 and the disease allele (chi2 = 4.829, P < 0.028). This region has been implicated by several studies on BPD [Sjoholt et al. (2004); Mol Psychiatry 9(6):621-629; Washizuka et al. (2004); Biol Psychiatry 56(7):483-489; Pickard et al. (2005); Psychiatr Genet 15(1):37-44], SCZ [Kikuchi et al. (2003); J Med Dent Sci 50(3):225-229; Babovic-Vuksanovic et al. (2004); Am J Med Genet 124(3):318-322] and also as a shared region between the two diseases [Ishiguro et al. (2001); J Neural Transm 108(7):849-854; Reyes et al. (2002); Mol Psychiatry 7(4):337-339; Craddock et al. (2005); J Med Genet 42(3):193-204]. Our findings provide an independent validation of the above reports, and suggest the presence of susceptibility loci for psychoses in this region.
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Cromosomas Humanos Par 18/genética , Predisposición Genética a la Enfermedad , Desequilibrio de Ligamiento/genética , Polimorfismo Genético , Trastornos Psicóticos/genética , Esquizofrenia/genética , Genotipo , Humanos , India , Escala de Lod , LinajeRESUMEN
A series of G-rich oligonucleotides able to form tetraplexes has been studied by FTIR spectroscopy. Characteristic markers of the formation of guanine tetrads are given. Moreover, we propose a new marker discriminating between parallel and antiparallel tetraplexes: the position of the C6O6 guanine carbonyl stretching vibration. In intermolecular parallel tetrameric structures formed by four separate strands this absorption is observed at 1693 cm-1 while for antiparallel tetrameric structures, either intramolecular or formed by dimerization of hairpins, this vibrational mode is observed at 1682 cm-1. These shifts to higher wavenumbers, when compared to the position of a free guanine C6O6 carbonyl stretching vibration observed at 1666 cm-1(Deltanu=27 cm-1 for parallel tetraplexes and Deltanu=16 cm-1 for antiparallel tetraplexes) reflect different strand orientations in the structures. This marker has been used to evidence the possibility of an antiparallel-parallel tetraplex reorganization for Oxytricha nova d(G4T4G4) and d((G4T4)3G4) and human d(G3T2AG3) telomeric sequences induced by Na+/K+ or Na+/Ca2+ ion exchange. Formation of the guanine tetrads, characterization of the phosphate geometries and of the sugar conformations have also been obtained by FTIR for the different tetraplexes.
Asunto(s)
ADN/química , Guanina/química , Vibración , Animales , Conformación de Carbohidratos , ADN Protozoario/química , Óxido de Deuterio/química , G-Cuádruplex , Humanos , Enlace de Hidrógeno , Conformación de Ácido Nucleico , Oxytricha , Fosfatos/química , Espectroscopía Infrarroja por Transformada de Fourier , Telómero/genéticaRESUMEN
OBJECTIVES: To understand the population variation and haplotypes of Huntington's disease (HD) in India we have analysed CAG repeats at the HD locus together with closely linked polymorphisms in both HD patients and normal controls. MATERIALS AND METHODS: The CAG repeat and linked polymorphisms were analysed in 30 Indian HD families together with 250 ethnically matched controls using fluorescent polymerase chain reaction (PCR) based size estimation. RESULTS: CAG repeats at the HD locus in the normal population showed a mean size of 17.99 +/- 2.66 repeats (range nine to 33 repeats). The HD mutation in our families did not show any significant association with either the (CCG)7 or (CCG)10 allele while haplotype analysis suggested the over-representation of the 7-2-I (CCG-D4s127-Delta 2642 loci) haplotype in a subset of families. CONCLUSION: The distribution of CAG repeats in the normal population suggests a higher prevalence of HD, closer to that seen in Western Europe. Haplotype analysis suggests the presence of a founder mutation in a subset of families and provides evidence for multiple and geographically distinct origins for the HD mutation in India.
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Ligamiento Genético/genética , Enfermedad de Huntington/genética , Polimorfismo Genético/genética , Análisis de Secuencia , Repeticiones de Trinucleótidos/genética , Femenino , Variación Genética/genética , Haplotipos/genética , Humanos , Enfermedad de Huntington/epidemiología , India/epidemiología , Masculino , Familia de Multigenes/genética , Reacción en Cadena de la PolimerasaRESUMEN
OBJECTIVE: A better understanding of human genetic variation is important in assessing disease epidemiology and phenotypic variation, and may be critical in evaluating genetic aspects of common genetic diseases, such as schizophrenia, bipolar disease and Parkinson's. These diseases are particularly difficult to investigate as there are few peripheral markers, and although a genetic aetiology has long been suspected, robust findings have been hard to establish. METHODS: Variations in alleles at 13 tri-nucleotide gene loci expressed in the brain and implicated in several neurodegenerative diseases, as well as certain other loci, were examined in the Indian population for comparison with other major ethnic groups. RESULTS AND CONCLUSION: In the Indian population, the distribution of alleles at the Machado-Joseph disease locus was similar to the Western European pattern of distribution. Analysis of haplotypes at the locus for Huntington's disease suggested multiple origins, and possible effects of population admixture because of the recent history of the country. At other alleles of neuropsychiatric interest (dopamine receptor, serotonin receptor, serotonin transporter, alcohol dehydrogenase), allele frequencies in the Indian population differed from other populations. Interspecies comparison suggests a gradual expansion in repeat size, with the exception of the CLOCK gene, which displays a contraction of CAG repeat numbers. World-wide differences in disease phenotypes need to be explored, and an appreciation of their genetic basis may provide a window of opportunity for improving our knowledge of the underlying genetic mechanisms.
RESUMEN
Spinocerebellar ataxia 2 (SCA2) is an autosomal dominant neurodegenerative disorder that results from the expansion of a cryptic CAG repeat within the exon 1 of the SCA2 gene. The CAG repeat in normal individuals varies in length from 14 to 31 repeats and is frequently interrupted by one or more CAA triplets, whereas the expanded alleles contain a pure uninterrupted stretch of 34 to 59 CAG repeats. We have previously reported the presence of a limited pool of 'ancestral' or 'at risk' haplotypes for the expanded SCA2 alleles in the Indian population. We now report the identification of two novel single nucleotide polymorphisms (SNPs) in exon 1 of the SCA2 gene and their characterization in 215 normal and 64 expanded chromosomes. The two biallelic SNPs distinguished two haplotypes, GT and CC, each of which formed a predominant haplotype associated with normal and expanded SCA2 alleles. All the expanded alleles segregated with CC haplotype, which otherwise was associated with only 29.3% of the normal chromosomes. CAA interspersion analysis revealed that majority of the normal alleles with CC haplotype were either pure or lacked the most proximal 5' CAA interruption. The repeat length variation at SCA2 locus also appeared to be polar with changes occurring mostly at the 5' end of the repeat. Our results demonstrate that CAA interruptions play an important role in conferring stability to SCA2 repeat and their absence predisposes alleles towards instability and pathological expansion. Our study also provides new haplotypes associated with SCA2 that should prove useful in further understanding the mutational history and mechanism of repeat instability at the SCA2 locus.
Asunto(s)
Proteínas/genética , Degeneraciones Espinocerebelosas/genética , Repeticiones de Trinucleótidos/genética , Alelos , Animales , Ataxinas , Cercopithecidae/genética , ADN/química , ADN/genética , Análisis Mutacional de ADN , Evolución Molecular , Femenino , Variación Genética , Gorilla gorilla/genética , Haplotipos , Humanos , Macaca mulatta/genética , Macaca radiata/genética , Masculino , Repeticiones de Microsatélite , Datos de Secuencia Molecular , Proteínas del Tejido Nervioso , Pan troglodytes/genética , Papio/genética , Mutación Puntual/genética , Polimorfismo de Nucleótido Simple/genética , Expansión de Repetición de Trinucleótido/genéticaRESUMEN
BACKGROUND: Poly purine.pyrimidine sequences have the potential to adopt intramolecular triplex structures and are overrepresented upstream of genes in eukaryotes. These sequences may regulate gene expression by modulating the interaction of transcription factors with DNA sequences upstream of genes. RESULTS: A poly purine.pyrimidine sequence with the potential to adopt an intramolecular triplex DNA structure was designed. The sequence was inserted within a nucleosome positioned upstream of the beta-galactosidase gene in yeast, Saccharomyces cerevisiae, between the cycl promoter and gal 10 Upstream Activating Sequences (UASg). Upon derepression with galactose, beta-galactosidase gene expression is reduced 12-fold in cells carrying single copy poly purine.pyrimidine sequences. This reduction in expression is correlated with reduced transcription. Furthermore, we show that plasmids carrying a poly purine.pyrimidine sequence are not specifically lost from yeast cells. CONCLUSION: We propose that a poly purine.pyrimidine sequence upstream of a gene affects transcription. Plasmids carrying this sequence are not specifically lost from cells and thus no additional effort is needed for the replication of these sequences in eukaryotic cells.
RESUMEN
The secondary structure of DNA has been shown to be an important component in the mechanism of expansion of the trinucleotide repeats that are associated with many neurodegenerative disorders. Recently, expansion of a dodecamer repeat, (CCCCGCCCCGCG)n upstream of cystatin B gene has been shown to be the most common mutation associated with Progressive Myoclonus Epilepsy (EPM1) of Unverricht-Lundborg type. We have investigated structure of oligonucleotides containing one, two and three copies of the EPM1 repeat sequences at physiological pH. CD spectra and anomalous faster gel electrophoretic mobilty indicates formation of intramolecularly folded structures that are formed independent of concentration. Hydroxylamine probing allowed us to identify the C residues that are involved in C.G base pairing. P1 nuclease studies elucidated the presence of unpaired regions in the folded back structures. UV melting studies show biphasic melting curves for the oligonucleotides containing two and three EPM1 repeats. Our data suggests multiple hairpin structures for two and three repeat containing oligonucleotides. In this paper we show that oligonucleotides containing EPM1 repeat adopt secondary structures that may facilitate strand slippage thereby causing the expansion.
Asunto(s)
Cistatinas/genética , ADN/química , ADN/genética , Repeticiones de Minisatélite , Epilepsias Mioclónicas Progresivas/genética , Secuencia de Bases , Dicroismo Circular , Cistatina B , Electroforesis en Gel de Poliacrilamida , Calor , Humanos , Concentración de Iones de Hidrógeno , Hidroxilamina , Técnicas In Vitro , Sondas Moleculares , Conformación de Ácido Nucleico , Desnaturalización de Ácido Nucleico , Oligodesoxirribonucleótidos/química , Oligodesoxirribonucleótidos/genética , Endonucleasas Específicas del ADN y ARN con un Solo FilamentoRESUMEN
The most common mutation associated with Progressive Myoclonus Epilepsy (EPM1) of Unverricht-Lundberg type is the expansion of a dodecamer repeat, d(CCCCGCCCCGCG)n. We show that the C-rich strand of this repeat (2-3 copies) forms intercalated i-motif structure at acidic pH as judged by CD spectroscopy and anomalous gel electrophoretic mobility. The stability of the structure increases with the increase in the length of the repeat. Transient formation of stable, folded back structure like i-motif could play an important role in the mechanism of expansion of this repeat.
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Cistatinas/genética , ADN/química , ADN/genética , Repeticiones de Minisatélite , Epilepsias Mioclónicas Progresivas/genética , Secuencia de Bases , Dicroismo Circular , Cistatina B , Electroforesis en Gel de Poliacrilamida , Humanos , Concentración de Iones de Hidrógeno , Técnicas In Vitro , Mutación , Conformación de Ácido Nucleico , Oligodesoxirribonucleótidos/química , Oligodesoxirribonucleótidos/genética , Espectrofotometría UltravioletaRESUMEN
Chromosome 22 has been implicated in schizophrenia and bipolar disorder in a number of linkage, association and cytogenetic studies. Recent evidence has also implicated CAG repeat tract expansion in these diseases. In order to explore the involvement of CAG repeats on chromosome 22 in these diseases, we have created an integrated map of all CAG repeats > or =5 on this chromosome together with microsatellite markers associated with these diseases using the recently completed nucleotide sequence of chromosome 22. Of the 52 CAG repeat loci identified in this manner, four of the longest repeat stretches in regions previously implicated by linkage analyses were chosen for further study. Three of the four repeat containing loci, were found in the coding region with the CAG repeats coding for glutamine and were expressed in the brain. All the loci studied showed varying degrees of polymorphism with one of the loci exhibiting two alleles of 7 and 8 CAG repeats. The 8-repeat allele at this locus was significantly overrepresented in both schizophrenia and bipolar patient groups when compared to ethnically matched controls, while alleles at the other three loci did not show any such difference. The repeat lies within a gene which shows homology to an androgen receptor related apoptosis protein in rat. We have also identified other candidate genes in the vicinity of this locus. Our results suggest that the repeats within this gene or other genes in the vicinity of this locus are likely to be implicated in bipolar disorder and schizophrenia.
Asunto(s)
Trastorno Bipolar/genética , Cromosomas Humanos Par 22 , Esquizofrenia/genética , Repeticiones de Trinucleótidos , Adulto , Anticipación Genética , Química Encefálica/genética , Femenino , Frecuencia de los Genes , Genotipo , Humanos , Masculino , Repeticiones de MicrosatéliteRESUMEN
BACKGROUND: Clinical data across the globe especially in genetic diseases like Huntington's disease (HD) is most helpful when collected using standardized formats. This helps in proper comparison of clinical and genetic data. METHODS: Herein, we report clinical data on 26 genetically confirmed HD patients from 19 Indian families predominantly from South India. Clinical data and evaluation was performed using standardized formats used by the Huntington Disease Study Group. RESULTS: Adult onset HD was commonest while Juvenile HD (onset <20 years) was observed in approximately 15% of patients. Chorea was the commonest presenting symptom (n=23, 88.5%) while remaining presented with psychiatric symptoms (n=3, 11.5%). Impairment of saccades was observed in approximately 75% of patients. Mean (SD) CAG repeats in the abnormal allele was 48.4 (8.7). Total motor score but not the total behavioral score worsens with duration of symptoms. The functional checklist score correlates with total motor score rather than with duration of symptoms. CONCLUSIONS: We detail clinical characteristics in genetically confirmed HD patients from a predominantly South Indian cohort. We observed a slightly higher occurrence of Juvenile HD. Functional disabilities in our patients correlate with worsening of motor rather than behavioral symptoms.
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Enfermedad de Huntington/genética , Enfermedad de Huntington/fisiopatología , Adolescente , Adulto , Edad de Inicio , Anciano , Ansiedad/etiología , Ansiedad/fisiopatología , Encéfalo/diagnóstico por imagen , Encéfalo/patología , Encéfalo/fisiopatología , Niño , Corea/etiología , Corea/fisiopatología , Trastornos del Conocimiento/etiología , Trastornos del Conocimiento/fisiopatología , Análisis Mutacional de ADN , Disartria/etiología , Disartria/fisiopatología , Distonía/etiología , Distonía/fisiopatología , Salud de la Familia , Femenino , Pruebas Genéticas , Humanos , Hipocinesia/etiología , Hipocinesia/fisiopatología , India , Genio Irritable/fisiología , Masculino , Persona de Mediana Edad , Rigidez Muscular/etiología , Rigidez Muscular/fisiopatología , Trastornos de la Motilidad Ocular/etiología , Trastornos de la Motilidad Ocular/fisiopatología , Estudios Prospectivos , Radiografía , Expansión de Repetición de Trinucleótido/genéticaRESUMEN
Circadian rhythms play a central role in diverse physiological phenomena and the recent years have witnessed the identification of a number of genes responsible for the maintenance of these rhythms. One of these is the Clock gene, which was first identified in mouse and subsequently in a large number of organisms, including humans. The human Clock gene has been proposed as a possible candidate for disorders affected by alterations of circadian rhythm, including bipolar disorder and schizophrenia. This gene contains a highly conserved polyglutamine motif, that in humans is coded for by CAG repeats. In view of the involvement of CAG repeat expansion in a number of neuro-psychiatric disorders, we have sought to determine the polymorphism status of CAG repeats at the Clock locus in humans. Our analysis of 190 unrelated individuals, who included patients suffering from bipolar disorder and schizophrenia, indicated that the repeat, which consisted of 6 CAG triplets, was not polymorphic in humans. An analysis of the repeat in non-human primates and other organisms revealed that the glutamine stretch is shortest in humans and baboons, and longest in Drosophila and zebrafish. A study of various Drosophila species revealed that the repeat number is highly polymorphic, ranging from 25 to 33 pure glutamine repeats. Unlike most other microsatellites, the CAG repeat stretch at the Clock locus in humans is smaller than its homologues in non-human primates. We propose that glutamine repeat size is functionally important in this gene and thus tightly regulated. The variation in repeat number is probably deleterious to the individual, resulting in the maintenance of a short and invariable repeat structure in the human population.
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Ritmo Circadiano/genética , Péptidos/genética , Polimorfismo Genético , Transactivadores/genética , Repeticiones de Trinucleótidos/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Trastorno Bipolar/genética , Proteínas CLOCK , Pollos , Mapeo Cromosómico , Secuencia Conservada , ADN/química , ADN/genética , Drosophila , Peces , Frecuencia de los Genes , Humanos , Ratones , Datos de Secuencia Molecular , Primates , Ratas , Esquizofrenia/genética , Homología de Secuencia de Ácido NucleicoRESUMEN
Angiotensin converting enzyme (ACE) gene I/D polymorphism has been associated with high altitude (HA) disorders as well as physical performance. We, however, envisage that the polymorphism may be associated with adaptation to the hypobaric hypoxia of altitude, thus facilitating physical performance. For this purpose, three unrelated adult male groups, namely (1) the Ladakhis (HLs), who reside at and above a height of 3600 m, (2) lowlanders, who migrated to Ladakh (MLLs), and (3) resident lowlanders (LLs), have been investigated. The HLs had significantly (p & 0.001) greater numbers of the II homozygotes and the ID heterozygotes than the DD homozygotes, the genotype distribution being 0.46, 0.43 and 0.11 for II, ID and DD genotypes respectively. The MLLs comprised 60% II homozygotes, which was higher (p & 0.001) than the HLs (46%). In the LLs, the heterozygotes were greater (p & 0.001) in number than the II and DD homozygotes. The I allele frequency was 0.72 in the MLLs, 0.67 in the HLs and 0.55 in the LLs. Polymorphism study suggested that the II genotype could be associated with altitude adaptation, which might influence physical efficiency.
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Mal de Altura/genética , Peptidil-Dipeptidasa A/genética , Adaptación Fisiológica/genética , Adaptación Fisiológica/fisiología , Adulto , Alelos , Elementos Transponibles de ADN , Genotipo , Humanos , India , MasculinoRESUMEN
Spinocerebellar ataxia 12 (SCA12) is a recently identified form of autosomal dominant cerebellar ataxia associated with the expansion of an unstable CAG repeat in the 5' untranslated region of the gene PPP2R2B. We analyzed 77 Indian families with autosomal dominant cerebellar ataxia phenotype and confirmed the diagnosis of SCA12 in 5 families, which included a total of 6 patients and 21 family members. The sizes of the expanded alleles ranged from 55 to 69 CAG repeats, and the sizes of the normal alleles ranged from 7 to 31 repeats. We believe our study is the first to demonstrate that SCA12 may not be as rare in some populations as previously thought.
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Proteínas del Tejido Nervioso/genética , Proteínas Nucleares/genética , Ataxias Espinocerebelosas/genética , Expansión de Repetición de Trinucleótido/genética , Adulto , Edad de Inicio , Ataxina-1 , Ataxinas , Femenino , Humanos , India , Masculino , Persona de Mediana Edad , Mutación , Linaje , Fenotipo , Ataxias Espinocerebelosas/diagnóstico , Ataxias Espinocerebelosas/fisiopatologíaRESUMEN
Bipolar affective disorder and schizophrenia are severe behavioral disorders with a lifetime risk of approximately 1% in the population worldwide. There is evidence that these diseases may manifest the phenomenon of anticipation similar to that seen in diseases caused by trinucleotide repeat expansions. A recent report has implicated a potassium channel-coding gene, KCNN3, which contains a polymorphic CAG repeat in its coding region, in schizophrenia and bipolar disorder. We have tried to confirm these findings in Indian patients suffering from bipolar disorder and schizophrenia. No statistically significant evidence for the presence of an excess of longer alleles in the patient population, as compared to ethnically matched controls, was found. However, an analysis of the difference of allele sizes revealed a significantly greater number of patients with schizophrenia having differences of allele sizes > or = 5 when compared to normal controls. This finding may be of functional significance as the KCNN3 protein is thought to act as a tetramer, and a large difference in allele sizes would result in an asymmetric molecule with a different number of glutamine residues in each monomer. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:744-748, 2000.
Asunto(s)
Trastorno Bipolar/genética , Canales de Potasio Calcio-Activados , Canales de Potasio/genética , Esquizofrenia/genética , Repeticiones de Trinucleótidos/genética , Adulto , Alelos , ADN/química , ADN/genética , Femenino , Frecuencia de los Genes , Humanos , India , Masculino , Análisis de Secuencia de ADN , Canales de Potasio de Pequeña Conductancia Activados por el CalcioRESUMEN
A variable number tandem repeat (VNTR) polymorphism consisting of multiple copies of a 17-bp repeat in the second intron of the serotonin transporter gene (SERT) has been reported. Different alleles of this VNTR have been found to be associated with bipolar disorder and schizophrenia. These findings have been confirmed in some populations, but disconfirmed in others. Furthermore, significant ethnic variations in the distribution of these alleles both in normal and patient populations also have been reported. We analyzed the VNTR polymorphism in 50 Indian patients with bipolar disorder and in ethnically matched controls. Two alleles corresponding to 10 and 12 repeats of the VNTR were found in both groups. There were no significant differences either in allele frequency or genotype frequency between the two groups. The nine-repeat allele that has been reported in Japanese and Caucasian populations was absent in our sample. Although it will be important to extend the present study in a larger sample, our initial results do not suggest any large association with alleles of the VNTR in the SERT gene and bipolar disorder in Indian patients. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:170-172, 2000.
Asunto(s)
Trastorno Bipolar/genética , Proteínas Portadoras/genética , Desequilibrio de Ligamiento/genética , Glicoproteínas de Membrana/genética , Proteínas de Transporte de Membrana , Proteínas del Tejido Nervioso , Alelos , Femenino , Genotipo , Humanos , India , Masculino , Repeticiones de Minisatélite/genética , Proteínas de Transporte de Serotonina en la Membrana PlasmáticaRESUMEN
Expansion of CTG/CAG trinucleotide repeats has been shown to cause a number of autosomal dominant cerebellar ataxias (ADCA) such as SCA1, SCA2, SCA3/ MJD, SCA6, SCA7, SCA8 and DRPLA. There is a wide variation in the clinical phenotype and prevalence of these ataxias in different populations. An analysis of ataxias in 42 Indian families indicates that SCA2 is the most frequent amongst all the ADCAs we have studied. In the SCA2 families, together with an intergenerational increase in repeat size, a horizontal increase with the birth order of the offspring was also observed, indicating an important role for parental age in repeat instability. This was strengthened by the detection of a pair of dizygotic twins with expanded alleles showing the same repeat number. Haplotype analysis indicates the presence of a common founder chromosome for the expanded allele in the Indian population. Polymorphism of CAG repeats in 135 normal individuals at the SCA loci studied showed similarity to the Caucasian population but was significantly different from the Japanese population.
Asunto(s)
Efecto Fundador , Genes Dominantes , Ataxias Espinocerebelosas/genética , Femenino , Humanos , India , Desequilibrio de Ligamiento , Masculino , Linaje , Repeticiones de TrinucleótidosRESUMEN
The genomes of Methanococcus jannaschii, Mycoplasma genitalium, Haemophilus influenzae, Archaeoglobus fulgidus, Helicobacter pylori, Treponema pallidum, Borrelia burgdorferri, Rickettsia prowazekeii, Mycobacterium tuberculosis, Methanobacterium thermoautotrophicum, Synechocystis sp. PCC6803, Bacillus subtilis, Chlamydia trachomatis, Pyrococcus horikoshii, Aquifex aeolicus, Mycoplasma pneumoniae and Escherichia coli have been analysed for the presence of polypurine.polypyrimidine tracts, in order to understand their distribution in these genomes. We observed a variation in abundance of such sequences in these bacteria, with the archaeal genomes forming a high-abundance group and the canonical eubacteria forming a low-abundance group. The genomes of M. tuberculosis and A. aeolicus are unique among the organisms analysed here in the abnormal underrepresentation and overrepresentation of polypurine.polypyrimidine, respectively. We also observe a strand bias, i.e., a preferential occurrence of polypurines in coding strands. It varies widely among the bacteria, from the very high bias in M. jannaschii to the slightly inverse bias in the parasitic genomes of T. pallidum and C. trachomatis. The extent of strand bias, however, cannot be explained on the basis of the GC-content of the genome, use of all-purine codons or an excess in the amino acids that are encoded by such codons. The probable causes and effects of this phenomenon are discussed.
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ADN Bacteriano/genética , Genoma Bacteriano , Purinas , Pirimidinas , Bacterias/genética , Proteínas Bacterianas/genética , Codón/genética , ADN Bacteriano/químicaRESUMEN
Several neurodegenerative diseases are caused by expansion of polyglutamine repeats in the affected proteins. In spino-cerebellar ataxia type 1 (SCA1), histidine interruptions have been reported to mitigate the pathological effects of long glutamine stretches. To understand this phenomenon, we investigated the conformational preferences of peptides containing both the uninterrupted polyglutamine stretches and those with histidine interruption(s) as seen in SCA1 normals. Our study suggests that substitution of histidines by glutamines induces a conformational change which results in decreased solubility and increased aggregation. Our findings also suggest that all the polyglutamine peptides with and without interruption(s) adopt a beta-structure and not random coil.