The long-term goal of this project is to understand the molecular basis of cilia formation and maintenance in vertebrate photoreceptor cells. In vertebrates, the assembly and maintenance of photoreceptor outer segments begins with the formation of a connecting cilium. The connecting cilium contains a microtubule- based axoneme that is anchored to the apical inner segment by a basal body. Cilia formation begins with the docking of basal bodies at the apical surface of the inner segment. Genetic mutations disrupting the assembly, structure, or function of basal bodies and/or cilia result in a spectrum of diseases known as ciliopathies. These multisyndromic disorders often present with retinal degeneration, kidney disease, mental retardation, and polydactyly. In the current application, we will utilize loss-of-function strategies in zebrafish to investigate the mechanisms controlling basal body localization.
In Specific Aim 1, we will test the hypothesis that the dynein/dynactin complex regulates the apical transport of basal bodies preceding cilia formation by examining zebrafish mutants in dynein and the p150 and p50 subunits of dynactin.
In Specific Aim 2, we provide preliminary evidence that basal bodies show a highly polarized arrangement within the adult zebrafish retina. We will directly test the hypothesis that the PCP pathway regulates this patterning and is essential for photoreceptor survival.
In Specific Aim 3, we will examine zebrafish carrying null mutations in the Joubert Syndrome gene arl13b for retinal phenotypes. Proposed experiments will also test the requirement of the GTPase domain and a ciliary-targeting sequence RVxPx for Arl13b function. We will also test arl13b for functional interactions with Bardet-Biedl Syndrome (BBS) genes, and components of the PCP pathway. These interactions will identify potential second-site modifiers that enhance expression of photoreceptor phenotypes. The results of these studies will reveal novel mechanisms required for basal body placement prior to cilia formation and to identify novel genetic interactions that influence hereditary blindness.

Public Health Relevance

The docking and anchoring of the basal body is essential for the formation of the connecting cilium and outer segment of vertebrate photoreceptors. The cilia/basal body structure is a complex organelle of great clinical importance because defects in cilia positioning, assembly or function lead to retinal degeneration, kidney disorders, mental retardation, situs inversus, polydactyly, and other conditions. An understanding of the mechanisms that control the cilia formation will lead to the development of treatments for ciliary diseases.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
2R01EY017037-07
Application #
8370330
Study Section
Special Emphasis Panel (BVS)
Program Officer
Neuhold, Lisa
Project Start
2006-01-01
Project End
2012-11-30
Budget Start
2012-09-30
Budget End
2012-11-30
Support Year
7
Fiscal Year
2012
Total Cost
$357,228
Indirect Cost
Name
Texas A&M University
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
020271826
City
College Station
State
TX
Country
United States
Zip Code
77845
DiCicco, Rose M; Bell, Brent A; Kaul, Charles et al. (2014) Retinal regeneration following OCT-guided laser injury in zebrafish. Invest Ophthalmol Vis Sci 55:6281-8
Krock, Bryan L; Perkins, Brian D (2014) The Par-PrkC polarity complex is required for cilia growth in zebrafish photoreceptors. PLoS One 9:e104661
Wasfy, Meagan M; Matsui, Jonathan I; Miller, Jessica et al. (2014) myosin 7aa(-/-) mutant zebrafish show mild photoreceptor degeneration and reduced electroretinographic responses. Exp Eye Res 122:65-76
Ramsey, Michelle; Perkins, Brian D (2013) Basal bodies exhibit polarized positioning in zebrafish cone photoreceptors. J Comp Neurol 521:1803-16
Wright, Rachel N; Hong, Dong-Hyun; Perkins, Brian (2011) Misexpression of the constitutive Rpgr(ex1-19) variant leads to severe photoreceptor degeneration. Invest Ophthalmol Vis Sci 52:5189-201
Hudak, Leah M; Lunt, Shannon; Chang, Chi-Hsuan et al. (2010) The intraflagellar transport protein ift80 is essential for photoreceptor survival in a zebrafish model of jeune asphyxiating thoracic dystrophy. Invest Ophthalmol Vis Sci 51:3792-9
Krock, Bryan L; Mills-Henry, Ishara; Perkins, Brian D (2009) Retrograde intraflagellar transport by cytoplasmic dynein-2 is required for outer segment extension in vertebrate photoreceptors but not arrestin translocation. Invest Ophthalmol Vis Sci 50:5463-71
Sukumaran, Sujita; Perkins, Brian D (2009) Early defects in photoreceptor outer segment morphogenesis in zebrafish ift57, ift88 and ift172 Intraflagellar Transport mutants. Vision Res 49:479-89
Lunt, Shannon C; Haynes, Tony; Perkins, Brian D (2009) Zebrafish ift57, ift88, and ift172 intraflagellar transport mutants disrupt cilia but do not affect hedgehog signaling. Dev Dyn 238:1744-59
Insinna, Christine; Pathak, Narendra; Perkins, Brian et al. (2008) The homodimeric kinesin, Kif17, is essential for vertebrate photoreceptor sensory outer segment development. Dev Biol 316:160-70

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