There has been remarkable progress in identifying the genetic basis for many types of inherited neurodegenerative disease. Despite this progress, genetic factors that contribute to the cause and progression of sporadic neurodegenerative disease remain generally unknown. Furthermore, in most instances, the genetic factors that influence the age of onset and rate of progression for many forms of inherited neurodegenerative disease remain to be identified. A better understanding of the genetic factors that are involved in neurodegenerative disease may not only help elucidate disease cause and progression, but could greatly expand the repertoire of molecular targets that are available for generating therapeutic interventions. One approach toward this goal has been to use forward genetic screens in model organisms to identify new genes that, when mutated or knocked down, either cause neurodegeneration or modify the progression of neurodegeneration. Using a forward genetic approach in Drosophila, we have recently demonstrated that the mutations in the presynaptic Dynein/Dynactin protein complex cause NMJ degeneration, as do mutations in the Spectrin/Ankyrin skeleton. Importantly, mutations in both the Dynein/Dynactin complex and Spectrin are associated with neuromuscular degenerative disease in human, establishing the relevance of our model system. In this grant proposal we report the identification of two new genes that, when mutated, cause neuromuscular degeneration in Drosophila. First we have identified mutations in the Drosophila homologue of adducin, an actin capping protein that binds to the Spectrin/Ankyrin skeleton. The identification of Adducin is particularly exciting because Adducin may represent a regulated link between the dynamic Actin cytoskeleton and the stabilizing function of the Spectrin/Ankyrin network. The second mutation that we recently identified disrupts a previously uncharacterized zinc finger containing protein that we call zf520. We then provide in vivo genetic evidence that zf520 participates in a well-established lipid-kinase signaling cascade previously liked to neurodegeneration. Thus, zf520 may represent a novel genetic link between a potent intracellular signaling system and the mechanisms of neuromuscular degeneration. In this grant we proposed to characterize the function of adducin and zf520 in the mechanisms of neuromuscular degeneration. Finally, we propose to continue our productive forward genetic screen to identify additional mutations that cause NMJ degeneration in Drosophila.
A better understanding of the genetic factors that are involved in neurodegenerative disease may not only help elucidate disease cause and progression, but could greatly expand the repertoire of molecular targets that are available for generating therapeutic interventions. In a large-scale forward genetic screen we have identified mutations in two new genes that cause neuromuscular degeneration. We propose to define the function of these genes at the neuromuscular junction, thereby significantly advancing our understanding of the genetic factors that may contribute to neuromuscular degenerative disease.
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