Despite significant advances in our understanding of degenerative diseases of the brainstem and retina, the pathways that underlie most of these disease processes remain undefined. Furthermore, the basis for cell-type specific degeneration and neuron cell death in many important neurological and retinal diseases is unknown. With these issues in mind, we hypothesized that delineation of the molecular basis of the neurological mouse mutant, Purkinje cell degeneration (pcd), would yield insights into how and why certain types of neurons degenerate. pcd is an autosomal recessive mutation that produces a non-developmental degeneration of cerebellar Purkinje cells and retinal photoreceptors. To determine the basis of the degeneration in pcd, we mapped the pcd gene defect to a 1 cM region on chromosome 13 and then identified mutations in the Nna1 gene in two alleles of pcd. Nna1 is a predicted 1218 amino acid protein that has a zinc carboxypeptidase domain with highly conserved orthologues in human (NNA1) and Drosophila (NnaD). Additional homologues of Nna1 exist in mouse, human, moth, and worms, all of which retain the carboxypeptidase domain. Using the results and resources that we have generated, we now wish to advance our understanding of how loss of Nna1 function leads to cell-type specific neurodegeneration in pcd, and thereby determine if Nna1's pathway of action has implications for other diseases. To accomplish these goals, we will begin by confirming that Nna1 is the causal gene by attempting transgenic rescue of the entire pcd phenotype and of one selected neuronal population, namely Purkinje cells. We will seek the mutations responsible for remaining pcd alleles. We will study the expression characteristics of the Nna1 gene product, and will define the nature of neuronal death in pcd mice. We will evaluate Nna1 for carboxypeptidase activity and will determine if retention of carboxy-peptidase activity is required for successful transgenic rescue. To identify Nna1's pathway of action, we will use lines of Drosophila that carry NnaD loss-of-function alleles to perform modifier screens to identify NnaD interacting genes. We will characterize Nna1 interacting proteins detected in a yeast two-hybrid screen, and will compare the results of these two screens to guide future studies.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY014997-05
Application #
7486853
Study Section
Special Emphasis Panel (ZRG1-CDIN (01))
Program Officer
Neuhold, Lisa
Project Start
2004-09-01
Project End
2009-06-30
Budget Start
2008-09-01
Budget End
2009-06-30
Support Year
5
Fiscal Year
2008
Total Cost
$253,846
Indirect Cost
Name
University of Washington
Department
Pathology
Type
Schools of Medicine
DUNS #
605799469
City
Seattle
State
WA
Country
United States
Zip Code
98195
Guyenet, Stephan J; Mookerjee, Shona S; Lin, Amy et al. (2015) Proteolytic cleavage of ataxin-7 promotes SCA7 retinal degeneration and neurological dysfunction. Hum Mol Genet 24:3908-17
Dubinsky, Amy N; Dastidar, Somasish Ghosh; Hsu, Cynthia L et al. (2014) Let-7 coordinately suppresses components of the amino acid sensing pathway to repress mTORC1 and induce autophagy. Cell Metab 20:626-38
Batlevi, Yakup; La Spada, Albert R (2011) Mitochondrial autophagy in neural function, neurodegenerative disease, neuron cell death, and aging. Neurobiol Dis 43:46-51
Guyenet, Stephan J; Furrer, Stephanie A; Damian, Vincent M et al. (2010) A simple composite phenotype scoring system for evaluating mouse models of cerebellar ataxia. J Vis Exp :
Chakrabarti, Lisa; Zahra, Rabaab; Jackson, Stephen M et al. (2010) Mitochondrial dysfunction in NnaD mutant flies and Purkinje cell degeneration mice reveals a role for Nna proteins in neuronal bioenergetics. Neuron 66:835-47
Young, Jessica E; Martinez, Refugio A; La Spada, Albert R (2009) Nutrient deprivation induces neuronal autophagy and implicates reduced insulin signaling in neuroprotective autophagy activation. J Biol Chem 284:2363-73
Young, Jessica E; La Spada, Albert R (2009) Development of selective nutrient deprivation as a system to study autophagy induction and regulation in neurons. Autophagy 5:555-7
Chakrabarti, Lisa; Eng, Jeremiah; Ivanov, Nishi et al. (2009) Autophagy activation and enhanced mitophagy characterize the Purkinje cells of pcd mice prior to neuronal death. Mol Brain 2:24
Chakrabarti, Lisa; Eng, Jeremiah; Martinez, Refugio A et al. (2008) The zinc-binding domain of Nna1 is required to prevent retinal photoreceptor loss and cerebellar ataxia in Purkinje cell degeneration (pcd) mice. Vision Res 48:1999-2005
Chakrabarti, Lisa; Neal, James T; Miles, Michael et al. (2006) The Purkinje cell degeneration 5J mutation is a single amino acid insertion that destabilizes Nna1 protein. Mamm Genome 17:103-10