1995 — 1999 |
Elliott, Jeffrey L |
K08Activity Code Description: To provide the opportunity for promising medical scientists with demonstrated aptitude to develop into independent investigators, or for faculty members to pursue research aspects of categorical areas applicable to the awarding unit, and aid in filling the academic faculty gap in these shortage areas within health profession's institutions of the country. |
Regulation of Motor Neuron Survival in Vivo
The critical role of antioxidant enzymes in motor neuron survival has been established by the finding that missense mutations in the Cu/Zn superoxide dismutase (SOD) genes are responsible for a dominantly inherited form of amyotrophic lateral sclerosis (FALS). However, whether motor neuron loss in FALS results from a toxic gain in function by a mutant enzyme, or is related to diminished levels of Cu\Zn SOD activity is still unclear. The generation of transgenic mice heterozygous and homozygous for a Cu\Zn SOD gene deletion now allows definitive testing of the hypothesis that motor neuron survival in vivo is directly related to Cu\Zn SOD levels. In the work outlined, I will determine whether reductions of Cu/Zn SOD activity in these mice will lead to decreased motor neuron survival over time, preferential involvement of motor neurons as compared to other classes of neurons, and increased motor neuron vulnerability to axotomy. I will also test the idea that the motor neurons dying in these transgenic animals after axotomy will exhibit characteristics of apoptosis. The close relationship between antioxidant defenses and apoptosis is underscored by the observations that powerful inhibitors of apoptosis may in fact prevent death by antioxidant mechanisms. The bcl-2 family of genes, mammalian homologs of the ced-9 gene in C. elegans, represent one such class of molecules, and within this group there is evidence that bcl- XL may have the most relevance for the nervous system. Remarkably within another family of genes, mammalian homologs of the C. elegans ced-3 gene, one member ich-1s also appears to prevent apoptosis in vitro. Here, I propose to generate transgenic animals which overexpress either Bcl-XL or ICH-1s in motor neurons and then determine whether overexpression of these molecules is protective in acquired models of motor neuron degeneration. Furthermore, this project will determine whether overexpression of Bcl-XL or ICH-1s will preserve the phentoype of axotomized motor neurons with regard to neurotransmitter synthesis and functional reinnervation of muscle. Finally, I will compare expression of genes implicated in neuronal survival in both ALS-sensitive and ALS-resistant motor pools in an effort to identify molecules which account for the selective vulnerability of certain motor neuron populations in ALS. Overall, these experiments will test the idea that molecules related to antioxidant defenses or apoptosis regulate motor neuron survival in vivo. Results from these experiments will have important implications for the potential mechanisms underlying motor neuron disease as well as for possible therapeutic interventions.
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0.957 |
2001 — 2004 |
Elliott, Jeffrey L |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Neuronal-Glial Interaction in the Pathogenesis of Als @ University of Texas SW Med Ctr/Dallas
DESCRIPTION (Adapted from applicant's abstract): Because it is motor neurons that invariably die in amyotrophic lateral sclerosis (ALS), most attention has focused on these cells as the primary site where pathophysiologic injury is initiated. However, evidence from human autopsy studies and a transgenic mouse model of familial amyotrophic lateral sclerosis, suggests a potential role for glia in the pathogenesis of disease. To address the cell specific origin of mutant (m) Cu/Zn superoxide dismutase (SOD1) induced disease, we have generated lines of transgenic mice using glial or neuronal specific promoters which allow expression of MSOD1 restricted to either neuronal or glial population. These lines do not develop motor weakness, raising the possibility that disease expression requires both neuronal and glial dysfunction induced by mSOD1. To test this hypothesis, we will determine whether crossing glial and neuronal restricted transgenic lines expressing mSOD1 will reconstitute the disease process in mice and lead to motor neuron degeneration. We will also use a spinal cord organotypic slice model of motor neuron degeneration to address specific mechanisms underlying interactions in fALS, we will generate chimeric mice from wild type and conventional mSOD1 mice, as well as derive chimera from conventional mSOD1 mice and either glial or neuronal specific mSOD1 transgenic liens. These experiments will determine whether glial/neuronal dysfunction involves cell-cell autonomous processes and ascertain whether the disease can be rescued by normal functioning glia. Although the exact mechanism of mSOD1 toxicity is still unknown, recent evidence has supported a critical role for zinc and copper ions. Because neurons and glia both express a repertoire of genes related to zinc/copper binding including the metallothioneins (MTs), we predict that both cell types will manifest abnormal MT expression patterns. In addition, we hypothesize that targeted deletion of neuronal or glial MT genes will significantly accelerate mSOD1- induced disease. Overall, these experiments will test the hypothesis that both neuronal and astroglial dysfunction is required for manifestation of disease in a transgenic murine model of fALS. These results will provide critical insights into mechanisms underlying human motor neuron disease and have important implications for future therapeutic interventions.
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0.957 |
2008 — 2012 |
Elliott, Jeffrey L |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Mechanisms of Sod1 Toxicity in Als @ University of Texas SW Med Ctr/Dallas
[unreadable] DESCRIPTION (provided by applicant): Although the factors that regulate SOD1 entrance, processing and aggregation within mitochondria are not fully understood, copper chaperone for SOD1 (CCS), appears to be an important determinant of SOD1 presence within mitochondria. In vitro evidence suggests that direct CCS interaction with SOD1 facilitates the conversion of immature apo-SOD1, that is capable of transit into mitochondria, to a mature holo-SOD1 form that is retained within mitochondria. Whether over-expressing CCS in vivo will alter the sub-cellular distribution of SOD1 in a way that favors intra-mitochondrial SOD1 retention and consequently impact mutant SOD1 induced disease is unknown. To address these key questions of SOD1 biochemistry in vivo, we have generated transgenic mice expressing human CCS in high levels within the CNS and crossed them to G93A-SOD1 or wild type (WT) SOD1 transgenic mice. Both CCS transgenic mice and CCS/WT-SOD1 dual transgenic mice are neurologically normal. In contrast, CCS/G93A-SOD1 dual transgenic mice develop accelerated neurological deficits, with a mean survival of 36 days compared to 242 days for G93A-SOD1 mice. Immuno-electron microscopy and sub-cellular fractionation studies on spinal cord show that G93A-SOD1 is enriched within mitochondria in the presence of CCS over-expression. Our results indicate that CCS over-expression in G93A-SOD1 mice produces severe mitochondrial pathology and accelerates disease course. The extent of these changes tells us that over-expressing CCS is changing a fundamental principle of G93A SOD1 induced neurological disease and raises two central questions. How is G93A SOD1 altered by CCS over-expression? How does this change in G93A SOD1 lead to the severe mitochondrial phenotype? Answering these two questions forms the basis for this grant proposal. Completion of the proposed aims in this grant will provide insights into the cellular and molecular mechanisms underlying one form of familial amyotrophic lateral sclerosis (ALS) related to mutations in the copper, zinc superoxide dismutase gene. [unreadable] [unreadable] [unreadable]
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0.993 |