RESUMO
We have used the slow myosin heavy chain (MyHC) 3 gene to study the molecular mechanisms that control atrial chamber-specific gene expression. Initially, slow MyHC 3 is uniformly expressed throughout the tubular heart of the quail embryo. As cardiac development proceeds, an anterior-posterior gradient of slow MyHC 3 expression develops, culminating in atrial chamber-restricted expression of this gene following chamberization. Two cis elements within the slow MyHC 3 gene promoter, a GATA-binding motif and a vitamin D receptor (VDR)-like binding motif, control chamber-specific expression. The GATA element of the slow MyHC 3 is sufficient for expression of a heterologous reporter gene in both atrial and ventricular cardiomyocytes, and expression of GATA-4, but not Nkx2-5 or myocyte enhancer factor 2C, activates reporter gene expression in fibroblasts. Equivalent levels of GATA-binding activity were found in extracts of atrial and ventricular cardiomyocytes from embryonic chamberized hearts. These observations suggest that GATA factors positively regulate slow MyHC 3 gene expression throughout the tubular heart and subsequently in the atria. In contrast, an inhibitory activity, operating through the VDR-like element, increased in ventricular cardiomyocytes during the transition of the heart from a tubular to a chambered structure. Overexpression of the VDR, acting via the VDR-like element, duplicates the inhibitory activity in ventricular but not in atrial cardiomyocytes. These data suggest that atrial chamber-specific expression of the slow MyHC 3 gene is achieved through the VDR-like inhibitory element in ventricular cardiomyocytes at the time distinct atrial and ventricular chambers form.
Assuntos
Regulação da Expressão Gênica no Desenvolvimento , Átrios do Coração/metabolismo , Cadeias Pesadas de Miosina/genética , Receptores de Calcitriol/metabolismo , Animais , Sequência de Bases , Sítios de Ligação , Células Cultivadas , Proteínas de Ligação a DNA/biossíntese , Proteínas de Ligação a DNA/genética , Fator de Transcrição GATA4 , Coração/embriologia , Átrios do Coração/citologia , Ventrículos do Coração/metabolismo , Dados de Sequência Molecular , Morfogênese , Cadeias Pesadas de Miosina/metabolismo , Regiões Promotoras Genéticas , Codorniz , Receptores do Ácido Retinoico/metabolismo , Fatores de Transcrição/biossíntese , Fatores de Transcrição/genéticaAssuntos
Custos de Medicamentos , Honorários Farmacêuticos , Inibidores da Agregação Plaquetária/economia , Análise Custo-Benefício , Custos de Medicamentos/estatística & dados numéricos , Custos de Medicamentos/tendências , Honorários Farmacêuticos/estatística & dados numéricos , Honorários Farmacêuticos/tendências , Humanos , Suíça , Estados UnidosRESUMO
The quail slow myosin heavy chain 3 (slow MyHC 3) gene is expressed in the developing heart and in slow muscles of the developing limb. It is first expressed in the pulsatile cardiac tube in the embryo, and as the heart chamberizes its expression becomes restricted to the atria. To identify regulatory elements responsible for atrial-specific expression, the 5' upstream region of slow MyHC 3 gene was investigated. An atrial regulatory domain (ARD1) between -840 and -680 acts as an atrial cell-specific enhancer in primary cardiocyte cultures. ARD1 also specifies atrial-specific expression in vivo when the ARD1/heterologous promoter was introduced into developing chick embryos by a replication-competent retroviral vector. ARD1 is the first atrial cell-specific enhancer to be identified. Fine deletion and mutation analysis within ARD1 defined a 40-base pair vitamin D3 receptor-like element that controls atrial cell-specific expression of the slow MyHC 3 gene by inhibiting its expression in ventricular cardiocytes.
Assuntos
Átrios do Coração/embriologia , Cadeias Pesadas de Miosina/metabolismo , Animais , Sequência de Bases , Células Cultivadas , Embrião de Galinha , Coturnix , Primers do DNA/química , Elementos Facilitadores Genéticos , Técnica Indireta de Fluorescência para Anticorpo , Regulação da Expressão Gênica no Desenvolvimento , Dados de Sequência Molecular , Regiões Promotoras Genéticas , RNA Mensageiro/genética , Deleção de SequênciaRESUMO
Schistosomiasis is among the most prevalent parasitic infections worldwide. However, current Global Burden of Disease (GBD) disability-adjusted life year estimates indicate that its population-level impact is negligible. Recent studies suggest that GBD methodologies may significantly underestimate the burden of parasitic diseases, including schistosomiasis. Furthermore, strain-specific disability weights have not been established for schistosomiasis, and the magnitude of human disease burden due to Schistosoma japonicum remains controversial. We used a decision model to quantify an alternative disability weight estimate of the burden of human disease due to S. japonicum. We reviewed S. japonicum morbidity data, and constructed decision trees for all infected persons and two age-specific strata, <15 years (y) and > or =15 y. We conducted stochastic and probabilistic sensitivity analyses for each model. Infection with S. japonicum was associated with an average disability weight of 0.132, with age-specific disability weights of 0.098 (<15 y) and 0.186 (> or =15 y). Re-estimated disability weights were seven to 46 times greater than current GBD measures; no simulations produced disability weight estimates lower than 0.009. Nutritional morbidities had the greatest contribution to the S. japonicum disability weight in the <15 y model, whereas major organ pathologies were the most critical variables in the older age group. GBD disability weights for schistosomiasis urgently need to be revised, and species-specific disability weights should be established. Even a marginal increase in current estimates would result in a substantial rise in the estimated global burden of schistosomiasis, and have considerable implications for public health prioritization and resource allocation for schistosomiasis research, monitoring, and control.(AU)