Candidate and Environment: Dr. Peter Fuerst will conduct the research contained within this proposal at Washington State University. Washington State University is an ideal environment in which to conduct advanced biomedical research using mouse models and in which to advance a research program. Research Proposal: The research we propose will use mouse models to identify the molecular mechanisms underpinning development of the retina. The mouse models, all developed by the applicant, include a conditional allele of the Down syndrome cell adhesion molecule, Dscam, as well as an allelic series of mouse mutant Dscam strains and a null allele of the Dscam homologue Dscam-like1 (Dscaml1). Dscam and Dscam- Like1 are essential for normal development of the nervous system and Dscam is proposed to contribute to the pathology of Down syndrome. In the retina, Dscam is required for soma mosaic spacing, regulation of cell number and neurite arborization and lamination. Our published results concerning Dscam and Dscaml1 are the first demonstrations of mutations found to ablate mosaic patterning and the first genes shown to mediate isoneuronal and heteroneuronal repulsion in vertebrates.
Specific Aims : We propose to use the Dscam and Dscaml1 mutant mouse models to discover mechanisms underpinning development of the retina and to probe the function of Dscam in the mammalian nervous system. This will be accomplished by testing the following hypotheses detailed in this research proposal. Hypotheses: 1) We will test the hypothesis that DSCAM mediates multiple distinct functions using an allelic series and conditional allele of Dscam mouse mutant lines to genetically and temporally isolate Dscam-dependent developmental processes. 2) We will test the hypothesis that DSCAM mediates adhesion between cell types and repulsion within cell types and that DSCAM activity in the retina is mediated by homophillic interactions and not by a ligand-receptor mechanism by using a conditional allele coupled to cell type specific deletion. 3) We will test the hypothesis that Dscam and Dscaml1 regulate normal developmental cell death. Long-term goals: This research will uncover fundamental aspects of neural organization and provide the funding necessary for Dr. Fuerst to establish a successful academic career focused on hypothesis driven biomedical research. Significance: Neurite arborization, regulation of cell number and soma mosaic spacing are fundamental aspects of neurodevelopment that are not currently well understood at the molecular level in vertebrates. Our preliminary research indicates that DSCAM plays a vital role in mediating these processes in the mammalian nervous system. Identifying mechanisms by which DSCAM functions using a series of mouse mutant alleles and a conditional allele will contribute to our understanding of nervous system development and the causation of disorders associated with neural dysgenesis and also contribute valuable research models to the neuroscience community.

Public Health Relevance

The primary goal of the proposed work is to understand how molecular recognition cues facilitate neural patterning. Research will focus on discovering the mechanisms by which two recognition cues;the Down Syndrome Cell Adhesion Molecule (Dscam) and its homologue Dscam-like1 (Dscaml1), mediate circuit formation within the retina. Both Dscam and Dscaml1 are required for neurite lamination, neurite arborization and regulation of cell number. Therefore, understanding the mechanism by which these molecules function will advance scientific understanding of neural development on multiple fronts. Furthermore, decreasing Dscam dosage decreases the incidence of retinal developmental cell death suggesting that the retina may provide an excellent system in which to model enhanced developmental cell death of neurons that occurs in Down syndrome patients, who overexpress Dscam as a result of Chromosome 21 trisomy.

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
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Biology and Diseases of the Posterior Eye Study Section (BDPE)
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Greenwell, Thomas
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University of Idaho
Schools of Arts and Sciences
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Bruce, Freyja M; Brown, Samantha; Smith, Jonathan N et al. (2017) DSCAM promotes axon fasciculation and growth in the developing optic pathway. Proc Natl Acad Sci U S A 114:1702-1707
Sukeena, Joshua M; Galicia, Carlos A; Wilson, Jacob D et al. (2016) Characterization and Evolution of the Spotted Gar Retina. J Exp Zool B Mol Dev Evol 326:403-421
Li, Shuai; Woodfin, Michael; Long, Seth S et al. (2016) IPLaminator: an ImageJ plugin for automated binning and quantification of retinal lamination. BMC Bioinformatics 17:36
Simmons, Aaron B; Bloomsburg, Samuel J; Billingslea, Samuel A et al. (2016) Pou4f2 knock-in Cre mouse: A multifaceted genetic tool for vision researchers. Mol Vis 22:705-17
Li, Shuai; Mitchell, Joe; Briggs, Deidrie J et al. (2016) Morphological Diversity of the Rod Spherule: A Study of Serially Reconstructed Electron Micrographs. PLoS One 11:e0150024
Simmons, Aaron B; Merrill, Morgan M; Reed, Justin C et al. (2016) Defective Angiogenesis and Intraretinal Bleeding in Mouse Models With Disrupted Inner Retinal Lamination. Invest Ophthalmol Vis Sci 57:1563-77
Fernandes, K A; Bloomsburg, S J; Miller, C J et al. (2016) Novel axon projection after stress and degeneration in the Dscam mutant retina. Mol Cell Neurosci 71:1-12
Li, Shuai; Sukeena, Joshua M; Simmons, Aaron B et al. (2015) DSCAM promotes refinement in the mouse retina through cell death and restriction of exploring dendrites. J Neurosci 35:5640-54
de Andrade, Gabriel Belem; Kunzelman, Landon; Merrill, Morgan M et al. (2014) Developmentally dynamic colocalization patterns of DSCAM with adhesion and synaptic proteins in the mouse retina. Mol Vis 20:1422-33
Nuhn, John S; Fuerst, Peter G (2014) Developmental localization of adhesion and scaffolding proteins at the cone synapse. Gene Expr Patterns 16:36-50

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