Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 135
Filtrar
Más filtros

Tipo del documento
Intervalo de año de publicación
1.
PLoS Genet ; 12(5): e1005994, 2016 05.
Artículo en Inglés | MEDLINE | ID: mdl-27149665

RESUMEN

African trypanosomes are mammalian pathogens that must regularly change their protein coat to survive in the host bloodstream. Chronic trypanosome infections are potentiated by their ability to access a deep genomic repertoire of Variant Surface Glycoprotein (VSG) genes and switch from the expression of one VSG to another. Switching VSG expression is largely based in DNA recombination events that result in chromosome translocations between an acceptor site, which houses the actively transcribed VSG, and a donor gene, drawn from an archive of more than 2,000 silent VSGs. One element implicated in these duplicative gene conversion events is a DNA repeat of approximately 70 bp that is found in long regions within each BES and short iterations proximal to VSGs within the silent archive. Early observations showing that 70-bp repeats can be recombination boundaries during VSG switching led to the prediction that VSG-proximal 70-bp repeats provide recombinatorial homology. Yet, this long held assumption had not been tested and no specific function for the conserved 70-bp repeats had been demonstrated. In the present study, the 70-bp repeats were genetically manipulated under conditions that induce gene conversion. In this manner, we demonstrated that 70-bp repeats promote access to archival VSGs. Synthetic repeat DNA sequences were then employed to identify the length, sequence, and directionality of repeat regions required for this activity. In addition, manipulation of the 70-bp repeats allowed us to observe a link between VSG switching and the cell cycle that had not been appreciated. Together these data provide definitive support for the long-standing hypothesis that 70-bp repeats provide recombinatorial homology during switching. Yet, the fact that silent archival VSGs are selected under these conditions suggests the 70-bp repeats also direct DNA pairing and recombination machinery away from the closest homologs (silent BESs) and toward the rest of the archive.


Asunto(s)
Secuencias Repetitivas de Ácidos Nucleicos/genética , Trypanosoma brucei brucei/genética , Tripanosomiasis Africana/genética , Glicoproteínas Variantes de Superficie de Trypanosoma/genética , Animales , Variación Antigénica/genética , Variación Antigénica/inmunología , Antígenos de Superficie/genética , Antígenos de Superficie/inmunología , Duplicación de Gen , Genómica , Secuencias Repetitivas de Ácidos Nucleicos/inmunología , Trypanosoma brucei brucei/inmunología , Trypanosoma brucei brucei/patogenicidad , Tripanosomiasis Africana/inmunología , Tripanosomiasis Africana/parasitología , Glicoproteínas Variantes de Superficie de Trypanosoma/inmunología
2.
Cardiol Young ; 29(10): 1282-1286, 2019 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-32167040

RESUMEN

Infective endocarditis is a microbial infection of the endothelial surface of the heart, predominantly the heart valves, that is associated with high mortality and morbidity. Few contemporary data exist regarding affected children in our context. AIMS AND OBJECTIVES: We aimed to describe the profile and treatment outcomes of infant and childhood endocarditis at our facilities. METHODS: This is a retrospective analysis of infants and children with endocarditis at two public sector hospitals in the Western Cape Province of South Africa over a 5-year period. Patients with "definite" and "possible" endocarditis according to Modified Duke Criteria were included in the review. RESULTS: Forty-nine patients were identified for inclusion; 29 had congenital heart disease as a predisposing condition; 64% of patients met "definite" and 36% "possible" criteria. The in-hospital mortality rate was 20%; 53% of patients underwent surgery with a post-operative mortality rate of 7.7%. The median interval from diagnosis to surgery was 20 days (interquartile range, 9-47 days). Valve replacement occurred in 28% and valve repair in 58%. There was a significant reduction in valvular dysfunction in patients undergoing surgery and only a marginal improvement in patients treated medically. Overall, 43% of patients had some degree of residual valvular dysfunction. CONCLUSION: Endocarditis is a serious disease with a high in-hospital mortality and presents challenges in making an accurate diagnosis. Despite a significant reduction in valvular dysfunction, a portion of patients had residual valvular dysfunction. Early surgery is associated with a lower mortality rate, but a higher rate of valve replacement compared with delayed surgery.


Asunto(s)
Procedimientos Quirúrgicos Cardíacos/mortalidad , Endocarditis/microbiología , Endocarditis/mortalidad , Endocarditis/cirugía , Adolescente , Niño , Preescolar , Endocarditis/diagnóstico , Femenino , Enfermedades de las Válvulas Cardíacas/epidemiología , Prótesis Valvulares Cardíacas/efectos adversos , Mortalidad Hospitalaria , Humanos , Lactante , Recién Nacido , Masculino , Estudios Retrospectivos , Factores de Riesgo , Sudáfrica , Factores de Tiempo , Tiempo de Tratamiento , Resultado del Tratamiento
3.
Eur J Contracept Reprod Health Care ; 24(5): 390-398, 2019 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-31517545

RESUMEN

Background: Multipurpose prevention technologies are needed to provide protection against HIV and sexually transmitted infections. Gel-based vaginal microbicides inserted via an applicator are prone to leakage. A novel device for vaginal drug delivery was developed to contain gel-based formulations, aiming to improve gel retention and reduce leakage. The objectives of this study were to assess acceptability and performance of a nonwoven vaginal delivery device. Methods: A nonwoven vaginal delivery device was prepared, pre-saturated with a commercially available water-based lubricant, with a finger pocket for insertion and string for removal. Quantitative and qualitative methods were used to collect data from interviews with 40 women and 10 male partners recruited from a sexual and reproductive health clinic in Durban, KwaZulu-Natal, South Africa. Women wore one device in the clinic and one device overnight or with their partner during intercourse. The primary endpoint was acceptability including comfort, ease of insertion and removal, and opinions on device attributes. Results: Most women said the device was 'easy' to insert and remove. Six women reported leakage after insertion and 34 reported having sexual intercourse while wearing the device. One woman was lost-to-follow-up and five women only wore the device overnight because their partners did not agree to intercourse with the inserted device. The best-liked attribute was the device's lubrication (22 women, 7 men); the least-liked was the removal string (9 women, 8 men). Conclusions: Data are promising for further development of this nonwoven device for vaginal drug delivery. Plain English summary Multipurpose prevention technologies (MPTs) that protect against HIV and sexually transmitted infections (STIs) are urgently needed. A variety of vaginal gel-based products are actively being researched; however, these products can often have challenges with vaginal leakage and retention. This research investigates the acceptability and performance of a nonwoven device to deliver vaginal gel formulations. The gel used in this study was a currently available marketed personal lubricant. In South Africa, 40 women (and 10 male partners) were recruited and given the opportunity to comment on various device attributes after insertion, overnight wear and sexual intercourse with their male partners. Generally, participants found the device easy to use and acceptable, where many factors possibly contributed to the device's acceptability (i.e., similarity to tampons, saturation with lubricant, minimal leakage, ease of insertion, comfort during intercourse and the male partners' willingness to have vaginal intercourse with the device in place). Further studies of the vaginal delivery device for acceptability, safety and efficacy using a gel-based formulation with an active ingredient are warranted.


Asunto(s)
Sistemas de Liberación de Medicamentos/psicología , Aceptación de la Atención de Salud/psicología , Parejas Sexuales/psicología , Enfermedades de Transmisión Sexual/prevención & control , Cremas, Espumas y Geles Vaginales/administración & dosificación , Administración Intravaginal , Adulto , Coito/psicología , Femenino , Humanos , Masculino , Investigación Cualitativa , Enfermedades de Transmisión Sexual/psicología , Sudáfrica , Resultado del Tratamiento , Adulto Joven
4.
Genes Dev ; 23(9): 1063-76, 2009 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-19369410

RESUMEN

Unusually for a eukaryote, genes transcribed by RNA polymerase II (pol II) in Trypanosoma brucei are arranged in polycistronic transcription units. With one exception, no pol II promoter motifs have been identified, and how transcription is initiated remains an enigma. T. brucei has four histone variants: H2AZ, H2BV, H3V, and H4V. Using chromatin immunoprecipitation (ChIP) and sequencing (ChIP-seq) to examine the genome-wide distribution of chromatin components, we show that histones H4K10ac, H2AZ, H2BV, and the bromodomain factor BDF3 are enriched up to 300-fold at probable pol II transcription start sites (TSSs). We also show that nucleosomes containing H2AZ and H2BV are less stable than canonical nucleosomes. Our analysis also identifies >60 unexpected TSS candidates and reveals the presence of long guanine runs at probable TSSs. Apparently unique to trypanosomes, additional histone variants H3V and H4V are enriched at probable pol II transcription termination sites. Our findings suggest that histone modifications and histone variants play crucial roles in transcription initiation and termination in trypanosomes and that destabilization of nucleosomes by histone variants is an evolutionarily ancient and general mechanism of transcription initiation, demonstrated in an organism in which general pol II transcription factors have been elusive.


Asunto(s)
Genoma de Protozoos/genética , Histonas/genética , Histonas/metabolismo , Proteínas Protozoarias/genética , Proteínas Protozoarias/metabolismo , Transcripción Genética/genética , Trypanosoma brucei brucei/genética , Animales , Cromatina/química , Inmunoprecipitación de Cromatina , ADN Polimerasa II/genética , Sistemas de Lectura Abierta/genética , Regiones Promotoras Genéticas/genética
5.
Ann Oncol ; 27(8): 1532-8, 2016 08.
Artículo en Inglés | MEDLINE | ID: mdl-27194814

RESUMEN

BACKGROUND: A mutation found in the BRCA1 or BRCA2 gene of a breast tumor could be either germline or somatically acquired. The prevalence of somatic BRCA1/2 mutations and the ratio between somatic and germline BRCA1/2 mutations in unselected breast cancer patients are currently unclear. PATIENTS AND METHODS: Paired normal and tumor DNA was analyzed for BRCA1/2 mutations by massively parallel sequencing in an unselected cohort of 273 breast cancer patients from south Sweden. RESULTS: Deleterious germline mutations in BRCA1 (n = 10) or BRCA2 (n = 10) were detected in 20 patients (7%). Deleterious somatic mutations in BRCA1 (n = 4) or BRCA2 (n = 5) were detected in 9 patients (3%). Accordingly, about 1 in 9 breast carcinomas (11%) in our cohort harbor a BRCA1/2 mutation. For each gene, the tumor phenotypes were very similar regardless of the mutation being germline or somatically acquired, whereas the tumor phenotypes differed significantly between wild-type and mutated cases. For age at diagnosis, the patients with somatic BRCA1/2 mutations resembled the wild-type patients (median age at diagnosis, germline BRCA1: 41.5 years; germline BRCA2: 49.5 years; somatic BRCA1/2: 65 years; wild-type BRCA1/2: 62.5 years). CONCLUSIONS: In a population without strong germline founder mutations, the likelihood of a BRCA1/2 mutation found in a breast carcinoma being somatic was ∼1/3 and germline 2/3. This may have implications for treatment and genetic counseling.


Asunto(s)
Proteína BRCA1/genética , Proteína BRCA2/genética , Neoplasias de la Mama/genética , Adulto , Anciano , Neoplasias de la Mama/epidemiología , Neoplasias de la Mama/patología , Femenino , Predisposición Genética a la Enfermedad , Mutación de Línea Germinal , Humanos , Persona de Mediana Edad , Mutación , Suecia/epidemiología
6.
Nature ; 459(7244): 278-81, 2009 May 14.
Artículo en Inglés | MEDLINE | ID: mdl-19369939

RESUMEN

Trypanosoma brucei is the causative agent of African sleeping sickness in humans and one of the causes of nagana in cattle. This protozoan parasite evades the host immune system by antigenic variation, a periodic switching of its variant surface glycoprotein (VSG) coat. VSG switching is spontaneous and occurs at a rate of about 10(-2)-10(-3) per population doubling in recent isolates from nature, but at a markedly reduced rate (10(-5)-10(-6)) in laboratory-adapted strains. VSG switching is thought to occur predominantly through gene conversion, a form of homologous recombination initiated by a DNA lesion that is used by other pathogens (for example, Candida albicans, Borrelia sp. and Neisseria gonorrhoeae) to generate surface protein diversity, and by B lymphocytes of the vertebrate immune system to generate antibody diversity. Very little is known about the molecular mechanism of VSG switching in T. brucei. Here we demonstrate that the introduction of a DNA double-stranded break (DSB) adjacent to the approximately 70-base-pair (bp) repeats upstream of the transcribed VSG gene increases switching in vitro approximately 250-fold, producing switched clones with a frequency and features similar to those generated early in an infection. We were also able to detect spontaneous DSBs within the 70-bp repeats upstream of the actively transcribed VSG gene, indicating that a DSB is a natural intermediate of VSG gene conversion and that VSG switching is the result of the resolution of this DSB by break-induced replication.


Asunto(s)
Variación Antigénica/genética , Roturas del ADN de Doble Cadena , Desoxirribonucleasas de Localización Especificada Tipo II/metabolismo , Modelos Genéticos , Proteínas de Saccharomyces cerevisiae/metabolismo , Trypanosoma brucei brucei/genética , Trypanosoma brucei brucei/inmunología , Animales , Reparación del ADN/genética , Replicación del ADN , Desoxirribonucleasas de Localización Especificada Tipo II/genética , Conversión Génica/genética , Reacción en Cadena de la Polimerasa , Saccharomyces cerevisiae/enzimología , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Análisis de Secuencia , Glicoproteínas Variantes de Superficie de Trypanosoma/genética , Glicoproteínas Variantes de Superficie de Trypanosoma/inmunología
7.
Mol Microbiol ; 87(1): 196-210, 2013 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-23216794

RESUMEN

Binding of the Origin Recognition Complex (ORC) to replication origins is essential for initiation of DNA replication, but ORC has non-essential functions outside of DNA replication, including in heterochromatic gene silencing and telomere maintenance. Trypanosoma brucei, a protozoan parasite that causes human African trypanosomiasis, uses antigenic variation as a major virulence mechanism to evade the host's immune attack by expressing its major surface antigen, the Variant Surface Glycoprotein (VSG), in a monoallelic manner. An Orc1/Cdc6 homologue has been identified in T. brucei, but its role in DNA replication has not been directly confirmed and its potential involvement in VSG repression or switching has not been thoroughly investigated. In this study, we show that TbOrc1 is essential for nuclear DNA replication in mammalian-infectious bloodstream and tsetse procyclic forms (BF and PF). Depletion of TbOrc1 resulted in derepression of telomere-linked silent VSGs in both BF and PF, and increased VSG switching particularly through the in situ transcriptional switching mechanism. TbOrc1 associates with telomere repeats but appears to do so independently of two known T. brucei telomere proteins, TbRAP1 and TbTRF. We conclude that TbOrc1 has conserved functions in DNA replication and is also required to control telomere-linked VSG expression and VSG switching.


Asunto(s)
Silenciador del Gen , Complejo de Reconocimiento del Origen/genética , Trypanosoma brucei brucei/genética , Glicoproteínas Variantes de Superficie de Trypanosoma/genética , Variación Antigénica , Replicación del ADN , ADN Protozoario/biosíntesis , ADN Protozoario/genética , Genes Protozoarios , Glicoproteínas de Membrana/genética , Complejo de Reconocimiento del Origen/metabolismo , Regiones Promotoras Genéticas , Trypanosoma brucei brucei/metabolismo
8.
RNA ; 18(11): 1968-83, 2012 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-22966087

RESUMEN

RNA-binding proteins that target mRNA coding regions are emerging as regulators of post-transcriptional processes in eukaryotes. Here we describe a newly identified RNA-binding protein, RBP42, which targets the coding region of mRNAs in the insect form of the African trypanosome, Trypanosoma brucei. RBP42 is an essential protein and associates with polysome-bound mRNAs in the cytoplasm. A global survey of RBP42-bound mRNAs was performed by applying HITS-CLIP technology, which captures protein-RNA interactions in vivo using UV light. Specific RBP42-mRNA interactions, as well as mRNA interactions with a known RNA-binding protein, were purified using specific antibodies. Target RNA sequences were identified and quantified using high-throughput RNA sequencing. Analysis revealed that RBP42 bound mainly within the coding region of mRNAs that encode proteins involved in cellular energy metabolism. Although the mechanism of RBP42's function is unclear at present, we speculate that RBP42 plays a critical role in modulating T. brucei energy metabolism.


Asunto(s)
Metabolismo Energético/genética , Proteínas Protozoarias/metabolismo , ARN Mensajero/metabolismo , ARN Protozoario/metabolismo , Proteínas de Unión al ARN/metabolismo , Trypanosoma brucei brucei/genética , Regiones no Traducidas 3' , Secuencia de Aminoácidos , Sitios de Unión , Regulación de la Expresión Génica , Técnicas de Silenciamiento del Gen , Datos de Secuencia Molecular , Sistemas de Lectura Abierta , Polirribosomas/metabolismo , Unión Proteica , Estructura Terciaria de Proteína , Proteínas Protozoarias/genética , Proteínas Protozoarias/aislamiento & purificación , Interferencia de ARN , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/aislamiento & purificación , Homología de Secuencia de Aminoácido , Trypanosoma brucei brucei/crecimiento & desarrollo , Trypanosoma brucei brucei/metabolismo
9.
PLoS Pathog ; 8(8): e1002900, 2012.
Artículo en Inglés | MEDLINE | ID: mdl-22952449

RESUMEN

Trypanosoma brucei is a master of antigenic variation and immune response evasion. Utilizing a genomic repertoire of more than 1000 Variant Surface Glycoprotein-encoding genes (VSGs), T. brucei can change its protein coat by "switching" from the expression of one VSG to another. Each active VSG is monoallelically expressed from only one of approximately 15 subtelomeric sites. Switching VSG expression occurs by three predominant mechanisms, arguably the most significant of which is the non-reciprocal exchange of VSG containing DNA by duplicative gene conversion (GC). How T. brucei orchestrates its complex switching mechanisms remains to be elucidated. Recent work has demonstrated that an exogenous DNA break in the active site could initiate a GC based switch, yet the source of the switch-initiating DNA lesion under natural conditions is still unknown. Here we investigated the hypothesis that telomere length directly affects VSG switching. We demonstrate that telomerase deficient strains with short telomeres switch more frequently than genetically identical strains with long telomeres and that, when the telomere is short, switching preferentially occurs by GC. Our data supports the hypothesis that a short telomere at the active VSG expression site results in an increase in subtelomeric DNA breaks, which can initiate GC based switching. In addition to their significance for T. brucei and telomere biology, the findings presented here have implications for the many diverse pathogens that organize their antigenic genes in subtelomeric regions.


Asunto(s)
Variación Antigénica/genética , Variación Genética , Telómero/genética , Trypanosoma brucei brucei/genética , Glicoproteínas Variantes de Superficie de Trypanosoma/genética , ADN Protozoario/genética , Conversión Génica , Duplicación de Gen , Humanos , Fenotipo , Telomerasa/genética , Telomerasa/metabolismo , Telómero/metabolismo , Homeostasis del Telómero/genética , Trypanosoma brucei brucei/inmunología , Trypanosoma brucei brucei/metabolismo , Glicoproteínas Variantes de Superficie de Trypanosoma/inmunología , Glicoproteínas Variantes de Superficie de Trypanosoma/metabolismo
10.
PLoS Pathog ; 6(7): e1000992, 2010 Jul 08.
Artículo en Inglés | MEDLINE | ID: mdl-20628569

RESUMEN

Homologous recombination (HR) mediates one of the major mechanisms of trypanosome antigenic variation by placing a different variant surface glycoprotein (VSG) gene under the control of the active expression site (ES). It is believed that the majority of VSG switching events occur by duplicative gene conversion, but only a few DNA repair genes that are central to HR have been assigned a role in this process. Gene conversion events that are associated with crossover are rarely seen in VSG switching, similar to mitotic HR. In other organisms, TOPO3alpha (Top3 in yeasts), a type IA topoisomerase, is part of a complex that is involved in the suppression of crossovers. We therefore asked whether a related mechanism might suppress VSG recombination. Using a set of reliable recombination and switching assays that could score individual switching mechanisms, we discovered that TOPO3alpha function is conserved in Trypanosoma brucei and that TOPO3alpha plays a critical role in antigenic switching. Switching frequency increased 10-40-fold in the absence of TOPO3alpha and this hyper-switching phenotype required RAD51. Moreover, the preference of 70-bp repeats for VSG recombination was mitigated, while homology regions elsewhere in ES were highly favored, in the absence of TOPO3alpha. Our data suggest that TOPO3alpha may remove undesirable recombination intermediates constantly arising between active and silent ESs, thereby balancing ES integrity against VSG recombination.


Asunto(s)
Variación Antigénica/genética , ADN-Topoisomerasas de Tipo I/fisiología , Conversión Génica , Trypanosoma brucei brucei/genética , Glicoproteínas Variantes de Superficie de Trypanosoma/genética , Proteínas Bacterianas/genética , Proteínas Fúngicas , Humanos , Recombinación Genética , Trypanosoma brucei brucei/inmunología
11.
Nucleic Acids Res ; 38(15): 4946-57, 2010 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-20385579

RESUMEN

Transcription of protein-coding genes in trypanosomes is polycistronic and gene expression is primarily regulated by post-transcriptional mechanisms. Sequence motifs in the untranslated regions regulate mRNA trans-splicing and RNA stability, yet where UTRs begin and end is known for very few genes. We used high-throughput RNA-sequencing to determine the genome-wide steady-state mRNA levels ('transcriptomes') for approximately 90% of the genome in two stages of the Trypanosoma brucei life cycle cultured in vitro. Almost 6% of genes were differentially expressed between the two life-cycle stages. We identified 5' splice-acceptor sites (SAS) and polyadenylation sites (PAS) for 6959 and 5948 genes, respectively. Most genes have between one and three alternative SAS, but PAS are more dispersed. For 488 genes, SAS were identified downstream of the originally assigned initiator ATG, so a subsequent in-frame ATG presumably designates the start of the true coding sequence. In some cases, alternative SAS would give rise to mRNAs encoding proteins with different N-terminal sequences. We could identify the introns in two genes known to contain them, but found no additional genes with introns. Our study demonstrates the usefulness of the RNA-seq technology to study the transcriptional landscape of an organism whose genome has not been fully annotated.


Asunto(s)
Genoma de Protozoos , Poliadenilación , ARN Mensajero/metabolismo , Trans-Empalme , Trypanosoma brucei brucei/genética , Animales , Línea Celular , Perfilación de la Expresión Génica , Genes Protozoarios , Genómica , Intrones , Estadios del Ciclo de Vida/genética , Sitios de Empalme de ARN , ARN Mensajero/química , Análisis de Secuencia de ARN , Trypanosoma brucei brucei/crecimiento & desarrollo , Regiones no Traducidas
12.
Nucleic Acids Res ; 38(12): 3923-35, 2010 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-20215442

RESUMEN

Base J is a hypermodified DNA base localized primarily to telomeric regions of the genome of Trypanosoma brucei. We have previously characterized two thymidine-hydroxylases (TH), JBP1 and JBP2, which regulate J-biosynthesis. JBP2 is a chromatin re-modeling protein that induces de novo J-synthesis, allowing JBP1, a J-DNA binding protein, to stimulate additional J-synthesis. Here, we show that both JBP2 and JBP1 are capable of stimulating de novo J-synthesis. We localized the JBP1- and JBP2-stimulated J by anti-J immunoprecipitation and high-throughput sequencing. This genome-wide analysis revealed an enrichment of base J at regions flanking polymerase II polycistronic transcription units (Pol II PTUs) throughout the T. brucei genome. Chromosome-internal J deposition is primarily mediated by JBP1, whereas JBP2-stimulated J deposition at the telomeric regions. However, the maintenance of J at JBP1-specific regions is dependent on JBP2 SWI/SNF and TH activity. That similar regions of Leishmania major also contain base J highlights the functional importance of the modified base at Pol II PTUs within members of the kinetoplastid family. The regulation of J synthesis/localization by two THs and potential biological function of J in regulating kinetoplastid gene expression is discussed.


Asunto(s)
ADN Protozoario/metabolismo , Proteínas de Unión al ADN/metabolismo , Glucósidos/biosíntesis , Oxigenasas de Función Mixta/metabolismo , Proteínas Protozoarias/metabolismo , Trypanosoma brucei brucei/genética , Uracilo/análogos & derivados , Animales , Línea Celular , ADN Protozoario/química , Genoma de Protozoos , Histonas/análisis , ARN Polimerasa II/metabolismo , Timidina/metabolismo , Transcripción Genética , Trypanosoma brucei brucei/enzimología , Uracilo/biosíntesis
13.
Genet Mol Res ; 11(3): 3133-7, 2012 Sep 03.
Artículo en Inglés | MEDLINE | ID: mdl-23007991

RESUMEN

Chromosome microarray analysis of patients with developmental delay has provided evidence of small deletions or duplications associated with this clinical phenotype. In this context, a 7.1- to 8.7-Mb interstitial deletion of chromosome 16 is well documented, but within this interval a rare 200-kb deletion has recently been defined that appears to be associated with obesity, or developmental delay together with overgrowth. We report a patient carrying this rare deletion, who falls into the latter clinical category, but who also carries a second very rare deletion in 13q31.3. It remains unclear if this maternally inherited deletion acts as a second copy number variation leading to pathogenic variation, or is non-causal and the true modifiers are yet to be determined.


Asunto(s)
Deleción Cromosómica , Cromosomas Humanos Par 13/genética , Cromosomas Humanos Par 16/genética , Discapacidades del Desarrollo/complicaciones , Discapacidades del Desarrollo/genética , Trastornos del Crecimiento/complicaciones , Trastornos del Crecimiento/genética , Preescolar , Predisposición Genética a la Enfermedad , Humanos , Masculino
14.
Psychol Res Behav Manag ; 15: 2097-2105, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35983023

RESUMEN

Purpose: Maladaptive personality traits and some psychological functioning indicators have been linked to academic misbehaviour; yet their role is still poorly explored in medical students. This study aims to assess associations of academic misconduct with dark personality traits and psychological well-being. Methods: Five hundred and ninety-one medical students attending the first, third and fifth-year at one Portuguese medical school replied to the Dark Triad Dirty Dozen, Ryff's Psychological Well-Being Scales and an original Academic Misconduct Questionnaire, using a cross-sectional design. Multiple linear regression was performed to assess associations. Results: Fifth-year medical students who scored higher in Machiavellianism and psychological well-being and perceived greater peer fraud and lower penalty for cheating reported more academic misconduct. The explanatory power of the model was 16.6%. Machiavellianism showed the strongest associations with cheating, while sex and age were not significant predictors. Conclusion: This study offers relevant insights into how maladaptive personalities influence academic misconduct in medical students, and how this relationship is moulded by psychological and contextual factors. These findings can help guide institutional actions to foster academic integrity in future physicians.

15.
EMBO J ; 26(23): 4856-66, 2007 Nov 28.
Artículo en Inglés | MEDLINE | ID: mdl-17972917

RESUMEN

The vector-borne, protistan parasite Trypanosoma brucei is the only known eukaryote with a multifunctional RNA polymerase I that, in addition to ribosomal genes, transcribes genes encoding the parasite's major cell-surface proteins-the variant surface glycoprotein (VSG) and procyclin. In the mammalian bloodstream, antigenic variation of the VSG coat is the parasite's means to evade the immune response, while procyclin is necessary for effective establishment of trypanosome infection in the fly. Moreover, the exceptionally high efficiency of mono-allelic VSG expression is essential to bloodstream trypanosomes since its silencing caused rapid cell-cycle arrest in vitro and clearance of parasites from infected mice. Here we describe a novel protein complex that recognizes class I promoters and is indispensable for class I transcription; it consists of a dynein light chain and six polypeptides that are conserved only among trypanosomatid parasites. In accordance with an essential transcriptional function of the complex, silencing the expression of a key subunit was lethal to bloodstream trypanosomes and specifically affected the abundance of rRNA and VSG mRNA. The complex was dubbed class I transcription factor A.


Asunto(s)
Proteínas Portadoras/metabolismo , Proteínas de Drosophila/metabolismo , Transcripción Genética , Trypanosoma brucei brucei/metabolismo , Glicoproteínas Variantes de Superficie de Trypanosoma/química , Animales , Núcleo Celular/metabolismo , Ciclinas/metabolismo , Dineínas , Silenciador del Gen , Genes Protozoarios , Vectores Genéticos , Modelos Biológicos , Regiones Promotoras Genéticas , Mapeo de Interacción de Proteínas , Proteínas Protozoarias/química , ARN Mensajero/metabolismo , Factores de Transcripción/metabolismo , Glicoproteínas Variantes de Superficie de Trypanosoma/metabolismo
16.
Clin Genet ; 80(5): 435-43, 2011 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-21114665

RESUMEN

We describe the identification and clinical presentation of four individuals from three unrelated families with hemizygous deletions involving the DPYD gene at chromosome 1p21.3. DPYD encodes dihydropyrimidine dehydrogenase, which is the initial and rate-limiting enzyme in the catabolism of pyrimidine bases. All four individuals described met diagnostic criteria for autism spectrum disorder with severe speech delay. Patient 1's deletion was originally reported in 2008, and more detailed clinical information is provided. Subsequently, this male individual was found to have a missense mutation in the X-linked PTCHD1 autism susceptibility gene, which may also contribute to the phenotype. Patients 2 and 3 are siblings with a novel deletion encompassing the DPYD gene. In their mother, the genomic region deleted from chromosome 1p21.3 was inserted into chromosome 10. A fourth proband had a novel 10-kb intragenic deletion of exon 6 of the DPYD gene detected on a higher resolution microarray. Our study suggests that hemizygous deletions involving the DPYD locus present with variable phenotypes which can include speech delay and autistic features, and may also be influenced by additional mutations in other genes, issues which need to be considered in genetic counseling.


Asunto(s)
Trastornos Generalizados del Desarrollo Infantil/genética , Cromosomas Humanos Par 1/genética , Dihidrouracilo Deshidrogenasa (NADP)/genética , Adolescente , Adulto , Niño , Preescolar , Deleción Cromosómica , Cromosomas Humanos Par 10/genética , Femenino , Humanos , Masculino , Linaje
17.
PLoS Biol ; 6(7): e161, 2008 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-18597556

RESUMEN

To evade the host immune system, several pathogens periodically change their cell-surface epitopes. In the African trypanosomes, antigenic variation is achieved by tightly regulating the expression of a multigene family encoding a large repertoire of variant surface glycoproteins (VSGs). Immune evasion relies on two important features: exposing a single type of VSG at the cell surface and periodically and very rapidly switching the expressed VSG. Transcriptional switching between resident telomeric VSG genes does not involve DNA rearrangements, and regulation is probably epigenetic. The histone methyltransferase DOT1B is a nonessential protein that trimethylates lysine 76 of histone H3 in Trypanosoma brucei. Here we report that transcriptionally silent telomeric VSGs become partially derepressed when DOT1B is deleted, whereas nontelomeric loci are unaffected. DOT1B also is involved in the kinetics of VSG switching: in DeltaDOT1B cells, the transcriptional switch is so slow that cells expressing two VSGs persist for several weeks, indicating that monoallelic transcription is compromised. We conclude that DOT1B is required to maintain strict VSG silencing and to ensure rapid transcriptional VSG switching, demonstrating that epigenetics plays an important role in regulating antigenic variation in T. brucei.


Asunto(s)
Variación Antigénica/inmunología , Regulación Enzimológica de la Expresión Génica/inmunología , N-Metiltransferasa de Histona-Lisina/metabolismo , Trypanosoma brucei brucei/enzimología , Glicoproteínas Variantes de Superficie de Trypanosoma/inmunología , Animales , Variación Antigénica/genética , Silenciador del Gen , Histona Metiltransferasas , N-Metiltransferasa de Histona-Lisina/genética , Interacciones Huésped-Parásitos , Proteína Metiltransferasas , Trypanosoma brucei brucei/patogenicidad , Trypanosoma brucei brucei/fisiología , Glicoproteínas Variantes de Superficie de Trypanosoma/genética
19.
Eukaryot Cell ; 9(1): 148-54, 2010 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-19915072

RESUMEN

In most eukaryotes, RNA polymerase I (Pol I) exclusively transcribes long arrays of identical rRNA genes (ribosomal DNA [rDNA]). African trypanosomes have the unique property of using Pol I to also transcribe the variant surface glycoprotein VSG genes. VSGs are important virulence factors because their switching allows trypanosomes to escape the host immune system, a mechanism known as antigenic variation. Only one VSG is transcribed at a time from one of 15 bloodstream-form expression sites (BESs). Although it is clear that switching among BESs does not involve DNA rearrangements and that regulation is probably epigenetic, it remains unknown why BESs are transcribed by Pol I and what roles are played by chromatin structure and histone modifications. Using chromatin immunoprecipitation, micrococcal nuclease digestion, and chromatin fractionation, we observed that there are fewer nucleosomes at the active BES and that these are irregularly spaced compared to silent BESs. rDNA coding regions are also depleted of nucleosomes, relative to the rDNA spacer. In contrast, genes transcribed by Pol II are organized in a more compact, regularly spaced, nucleosomal structure. These observations provide new insight on antigenic variation by showing that chromatin remodeling is an intrinsic feature of BES regulation.


Asunto(s)
Nucleosomas/metabolismo , ARN Polimerasa I/metabolismo , Trypanosoma brucei brucei , Glicoproteínas Variantes de Superficie de Trypanosoma/metabolismo , Cromatina/química , Cromatina/metabolismo , Regulación de la Expresión Génica , Histonas/genética , Histonas/metabolismo , Conformación de Ácido Nucleico , ARN Polimerasa I/genética , Transcripción Genética , Trypanosoma brucei brucei/genética , Trypanosoma brucei brucei/metabolismo , Glicoproteínas Variantes de Superficie de Trypanosoma/genética
20.
Int J Cardiol ; 333: 119-126, 2021 06 15.
Artículo en Inglés | MEDLINE | ID: mdl-33607192

RESUMEN

BACKGROUND: Heart failure (HF), the dominant form of cardiovascular disease in Africans, is mainly due to hypertension, rheumatic heart disease and cardiomyopathy. Cardiomyopathies pose a great challenge because of poor prognosis and high prevalence in low- and middle-income countries (LMICs). Little is known about the etiology and outcome of cardiomyopathy in Africa. Specifically, the role of myocarditis and the genetic causes of cardiomyopathy are largely unidentified in Africans. METHOD: The African Cardiomyopathy and Myocarditis Registry Program (the IMHOTEP study) is a pan-African multi-centre, hospital-based cohort study, designed with the primary aim of describing the clinical characteristics, genetic causes, prevalence, management and outcome of cardiomyopathy and myocarditis in children and adults. The secondary aim is to identify barriers to the implementation of evidence-based care and provide a platform for trials and other intervention studies to reduce morbidity and mortality in cardiomyopathy. The registry consists of a prospective cohort of newly diagnosed (i.e., incident) cases and a retrospective (i.e., prevalent) cohort of existing cases from participating centres. Patients with cardiomyopathy and myocarditis will be subjected to a standardized 3-stage diagnostic process. To date, 750 patients have been recruited into the multi-centre pilot phase of the study. CONCLUSION: The IMHOTEP study will provide comprehensive and novel data on clinical features, genetic causes, prevalence and outcome of African children and adults with all forms of cardiomyopathy and myocarditis in Africa. Based on these findings, appropriate strategies for management and prevention of the cardiomyopathies in LMICs are likely to emerge.


Asunto(s)
Cardiomiopatías , Miocarditis , Adulto , África/epidemiología , Cardiomiopatías/diagnóstico , Cardiomiopatías/epidemiología , Cardiomiopatías/genética , Niño , Estudios de Cohortes , Humanos , Miocarditis/diagnóstico , Miocarditis/epidemiología , Miocarditis/terapia , Estudios Prospectivos , Sistema de Registros , Estudios Retrospectivos
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA