The primary cilium is critical to vertebrate development and the prevention of disease. Severe defects in this organelle lead to prenatal lethality in extreme cases and a variety of structural birth defects and degenerative diseases in less extreme cases. It is thought that the primary cilium serves as a cellular antenna to monitor the extracellular environment and feed information back to the cell to coordinate its action with that of the surrounding cells. A large number of signaling pathways are directly or indirectly regulated by cilia including hedgehog, left-right/nodal, Wnt, notch, IGF and PDGF. Understanding how the cilium is assembled and how the signaling environment is created and maintained is critical to understanding how this organelle functions in the etiology of human diseases. The cilium is assembled by the process of intraflagellar transport (IFT) where large protein complexes called IFT particles are carried along the ciliary microtubules by kinesin and dynein motors. The IFT system consists of about 20 proteins organized into two large complexes. The long-term objective of this work is to understand the function of the individual IFT particle proteins. Mutations in most Ift genes block ciliary assembly and also disrupt ciliary signaling. In the past, it has been difficult to separate the function of IFT in building a cilium, which is required for signaling, from functions directly in signaling. This proposal focuses on Ift25 and Ift27, which unlike most Ift genes in mouse are not required for ciliary assembly but like other Ift genes are required for hedgehog signaling. In that absence of IFT25 or IFT27, the hedgehog receptors patched-1 and smoothened are not trafficked properly and accumulate in cilia. This proposal addresses how IFT25 and IFT27 function to connect IFT to the dynamic movements of hedgehog components into and out of cilia. This will be addressed through a series of protein interaction studies, live cell imaging and mouse genetics.

Public Health Relevance

Severe defects in the primary cilium cause prenatal lethality while less severe defects result in a variety of diseases including polycystic kidney disease and blindness along with a group of syndromes called the ciliopathies. These syndromes, which include Bardet-Biedl, Meckel Gruber and Jeune Syndromes, often present with cystic kidney disease and blindness along with a variety of symptoms including obesity, mental retardation, and structural birth defects. This proposal seeks to understand the mechanism by which cilia are assembled and function to ultimately drive the identification of a treatment or cure for these diseases.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM060992-16
Application #
9180705
Study Section
Nuclear and Cytoplasmic Structure/Function and Dynamics Study Section (NCSD)
Program Officer
Gindhart, Joseph G
Project Start
2001-06-01
Project End
2018-11-30
Budget Start
2016-12-01
Budget End
2017-11-30
Support Year
16
Fiscal Year
2017
Total Cost
Indirect Cost
Name
University of Massachusetts Medical School Worcester
Department
Anatomy/Cell Biology
Type
Schools of Medicine
DUNS #
603847393
City
Worcester
State
MA
Country
United States
Zip Code
01655
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Desai, Paurav B; San Agustin, Jovenal T; Stuck, Michael W et al. (2018) Ift25 is not a cystic kidney disease gene but is required for early steps of kidney development. Mech Dev 151:10-17
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Monis, William J; Faundez, Victor; Pazour, Gregory J (2017) BLOC-1 is required for selective membrane protein trafficking from endosomes to primary cilia. J Cell Biol 216:2131-2150
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Liu, Hong; Li, Wei; Zhang, Yong et al. (2017) IFT25, an intraflagellar transporter protein dispensable for ciliogenesis in somatic cells, is essential for sperm flagella formation. Biol Reprod 96:993-1006

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