Biomedical subjects

Carlos J Miranda

Publications and source records attributed to Carlos J Miranda.

7 recordsLinked to original sources

PubMed2006

Gene expression profiling in frataxin deficient mice: microarray evidence for significant expression changes without detectable neurodegeneration.

Friedreich's ataxia (FRDA) is caused by reduction of frataxin levels to 5-35%. To better understand the biochemical sequelae of frataxin reduction, in absence of the confounding effects of neurodegeneration, we studied the gene expression profile of a mouse model expressing 25-36% of the normal frataxin levels, and not showing a detectable phenotype or neurodegenerative features. Despite having no overt phenotype, a clear microarray gene expression phenotype was observed. This phenotype followed the known regional susceptibility in this disease, most changes occurring in the spinal cord. Additionally, gene ontology analysis identified a clear mitochondrial component, consistent with previous findings. We were able to confirm a subset of changes in fibroblast cell lines from patients. The identification of a core set of genes changing early in the FRDA pathogenesis can be a useful tool in both clarifying the disease process and in evaluating new therapeutic strategies.

Animals↗

PubMed2004

Frataxin overexpressing mice.

Friedreich ataxia, the most common autosomal recessive ataxia, is caused by frataxin deficiency. Reduction of frataxin has been associated with iron accumulation and sensitivity to iron induced oxidative stress. To better understand the function of frataxin, transgenic mice (tgFxn) overexpressing human frataxin were generated. Iron metabolism parameters in tgFxn were normal and no signs of ataxia or other obvious abnormalities were observed, indicating that overexpression of frataxin in mouse is innocuous. Several hypotheses for frataxin function were evaluated in tgFxn mice. In particular, we observed that TgFxn mice show an altered response during hematopoietic differentiation, suggesting that frataxin may directly affect heme synthesis.

Animals↗

PubMed2004

Genomic structure, promoter activity, and developmental expression of the mouse homologue of the Machado-Joseph disease (MJD) gene.

Machado-Joseph disease (MJD) is a neurodegenerative disorder, caused by the expansion of the (CAG)n tract in the MJD gene. This encodes the protein ataxin-3, of unknown function. The mouse Mjd gene has a structure similar to that of its human counterpart and it also contains a TATA-less promoter. Its 5' flanking region contains conserved putative binding regions for transcription factors Sp1, USF, Arnt, Max, E47, and MyoD. Upon differentiation of P19 cells, the Mjd gene promoter is preferentially activated in endodermal and mesodermal derivatives, including cardiac and skeletal myocytes; and less so in neuronal precursors. Mouse ataxin-3 is ubiquitously expressed during embryonic development and in the adult, with strong expression in regions of the CNS affected in MJD. It is particularly abundant in all types of muscle and in ciliated epithelial cells, suggesting that it may be associated with the cytoskeleton and may have an important function in cell structure and/or motility.

5' Flanking Region↗

PubMed2003

Contributions of beta2-microglobulin-dependent molecules and lymphocytes to iron regulation: insights from HfeRag1(-/-) and beta2mRag1(-/-) double knock-out mice.

Genetic causes of hereditary hemochromatosis (HH) include mutations in the HFE gene, coding for a beta2-microglobulin (beta2m)-associated major histocompatibility complex class I-like protein. However, iron accumulation in patients with HH can be highly variable. Previously, analysis of beta2mRag1(-/-) double-deficient mice, lacking all beta2m-dependent molecules and lymphocytes, demonstrated increased iron accumulation in the pancreas and heart compared with beta2m single knock-out mice. To evaluate whether the observed phenotype in beta2mRag1(-/-) mice was due solely to the absence of Hfe or to other beta2m-dependent molecules, we generated HfeRag1(-/-) double-deficient mice. Our studies revealed that introduction of Rag1 deficiency in Hfe knock-out mice leads to heightened iron overload, mainly in the liver, whereas the heart and pancreas are relatively spared compared with beta2mRag1(-/-) mice. These results suggest that other beta2m-interacting protein(s) may be involved in iron regulation and that in the absence of functional Hfe molecules lymphocyte numbers may influence iron overload severity.

Animals↗

PubMed2003

Hfe deficiency increases susceptibility to cardiotoxicity and exacerbates changes in iron metabolism induced by doxorubicin.

The clinical use of doxorubicin (DOX), an anthracycline chemotherapeutic agent, is limited by cardiotoxicity. The possible involvement of iron in DOX-induced cardiotoxicity became evident from studies in which iron chelators were shown to be cardioprotective. Iron overload is found in hereditary hemochromatosis, a genetic disorder prevalent in individuals of European descent. We hypothesized that Hfe deficiency may increase susceptibility to DOX-induced toxicity. Acute cardiotoxicity and iron changes were studied after treatment with DOX in Hfe knock-out (Hfe-/-) mice and wild-type mice. DOX-induced iron metabolism changes were intensified in Hfe-/- mice, which accumulated significantly more iron in the heart, liver, and pancreas, but less in the spleen compared with wild-type mice. In addition, Hfe-deficient mice exhibited significantly greater sensitivity to DOX-induced elevations in serum creatine kinase and aspartate aminotransferase. Increased mortality after chronic DOX treatment was observed in Hfe-/- mice and Hfe+/-mice compared with wild-type mice. DOX-treated Hfe-/- mice had a higher degree of mitochondrial damage and iron deposits in the heart than did wild-type mice. These data demonstrate that Hfe deficiency in mice increases susceptibility to DOX-induced cardiotoxicity and suggest that genetic mutations related to defects in iron metabolism may contribute to its cardiotoxicity in humans.

Alanine Transaminase↗

PubMed2003

Iron metabolism in mice with partial frataxin deficiency.

Friedreich ataxia (FRDA), the most common autosomal recessive inherited ataxic disorder, is the consequence of deficiency of the mitochondrial protein frataxin, typically caused by homozygous intronic GAA expansions in the corresponding gene. The yeast frataxin homologue (yfh1p) is required for cellular respiration. Yfh1p appears to regulate mitochondrial iron homeostasis and protect from free radical toxicity. Complete loss of frataxin in knockout mice leads to early embryonic lethality, indicating an important role for frataxin during development. Heterozygous littermates with partial frataxin deficiency are apparently healthy and have no obvious phenotype. Here we evaluate iron metabolism and sensitivity to dietary and parenteral iron loading in heterozygote frataxin knockout mice (Fx(+/-)). Iron concentrations in the liver, heart, pancreas and spleen, and cellular iron distribution patterns were compared between wild type and Fx(+/-) mice. Response to parenteral iron challenge was not different between Fx(+/-) mice and wild type littermates, while sporadic iron deposits were observed in the hearts of dietary iron-loaded Fx(+/-) mice. Finally, we evaluated the effect of partial frataxin deficiency on susceptibility to cardiac damage in the mouse model of hereditary hemochromatosis (HH), the Hfe knockout mice. HH, an iron overload disease, is one of the most frequent genetic diseases in populations of European origin. By breeding Hfe(-/-) with Fx(+/-) mice, we obtained compound mutant mice lacking both Hfe and one frataxin allele. Sparse iron deposits in areas of mild to moderate cardiac fibrosis were found in the majority of these mice. However, they did not develop any neurological symptoms. Our studies indicate an association between frataxin deficiency, iron deposits and cardiac fibrosis, but no obvious association between iron accumulation and neurodegeneration similar to FRDA could be detected in our model. In addition, these results suggest that frataxin mutations may have a modifier role in HH, that predisposes to cardiomyopathy.

Animals↗

PubMed2002

Frataxin knockin mouse.

Friedreich ataxia is the consequence of frataxin deficiency, most often caused by a GAA repeat expansion in intron 1 of the corresponding gene. Frataxin is a mitochondrial protein involved in iron homeostasis. As an attempt to generate a mouse model of the disease, we introduced a (GAA)(230) repeat within the mouse frataxin gene by homologous recombination. GAA repeat knockin mice were crossed with frataxin knockout mice to obtain double heterozygous mice expressing 25-36% of wild-type frataxin levels. These mice were viable and did not develop anomalies of motor coordination, iron metabolism or response to iron loading. Repeats were meiotically and mitotically stable.

Alleles↗