RESUMEN
X-linked sideroblastic anemia with ataxia (XLSA/A) is a rare inherited disorder characterized by mild anemia and ataxia. XLSA/A is caused by mutations in the ABCB7 gene, which encodes a member of the ATP-binding cassette transporter family. Studies in yeast, mammalian cells, and mice have shown that ABCB7 functions in the transport of iron-sulfur (Fe-S) clusters into the cytoplasm. To further investigate the mechanism of this disease, we have identified and characterized the Caenorhabditis elegans homologue of the ABCB7 gene, abtm-1. We have studied the function of abtm-1 using mutants and RNAi. abtm-1-depleted animals produce arrested embryos that have morphogenetic defects and unusual premature, putative apoptotic events. abtm-1(RNAi) animals also show accumulation of ferric iron and increased oxidative stress. Despite the increased level of oxidative stress in abtm-1(RNAi) animals, they have an increased life span. We observed accumulation of DAF-16/FOXO in the nuclei of affected animals and elevation of the expression of SOD-3, a well established target of DAF-16, which may explain the increased life span extension of these animals. abtm-1 is strongly expressed in tissues with a high energy demand, and abtm-1(RNAi) animals have phenotypes that reflect the need for abtm-1 in these tissues. Finally, we show that reducing the function of other genes involved in Fe-S cluster production produces similar phenotypic consequences to abtm-1 loss of function. Therefore, ablation of abtm-1 in C. elegans provides a model in which to investigate the mechanism underlying XLSA/A.
Asunto(s)
Transportadoras de Casetes de Unión a ATP/metabolismo , Proteínas de Caenorhabditis elegans/fisiología , Caenorhabditis elegans/metabolismo , Regulación del Desarrollo de la Expresión Génica , Estrés Oxidativo , Transportadoras de Casetes de Unión a ATP/genética , Transportadoras de Casetes de Unión a ATP/fisiología , Animales , Apoptosis , Proteínas de Caenorhabditis elegans/genética , Muerte Celular , Citoplasma/metabolismo , ADN Complementario/metabolismo , Hierro/metabolismo , Proteínas de Unión a Hierro/metabolismo , Mitocondrias/metabolismo , Modelos Biológicos , Interferencia de ARN , FrataxinaRESUMEN
Inositol 1,4,5-trisphosphate (IP(3)) is an important second messenger in animal cells and is central to a wide range of cellular responses. The major intracellular activity of IP(3) is to regulate release of Ca(2+) from intracellular stores through IP(3) receptors (IP(3)Rs). We describe a system for the transient disruption of IP(3) signaling in the model organism Caenorhabditis elegans. The IP(3) binding domain of the C. elegans IP(3)R, ITR-1, was expressed from heat shock-induced promoters in live animals. This results in a dominant-negative effect caused by the overexpressed IP(3) binding domain acting as an IP(3) "sponge." Disruption of IP(3) signaling resulted in disrupted defecation, a phenotype predicted by previous genetic studies. This approach also identified two new IP(3)-mediated processes. First, the up-regulation of pharyngeal pumping in response to food is dependent on IP(3) signaling. RNA-mediated interference studies and analysis of itr-1 mutants show that this process is also IP(3)R dependent. Second, the tissue-specific expression of the dominant-negative construct enabled us to circumvent the sterility associated with loss of IP(3) signaling through the IP(3)R and thus determine that IP(3)-mediated signaling is required for multiple steps in embryogenesis, including cytokinesis and gastrulation.