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Wdpcp Affects Skeletogenesis via the Hedgehog Pathway

Langhans, Mark (2015) Wdpcp Affects Skeletogenesis via the Hedgehog Pathway. Doctoral Dissertation, University of Pittsburgh.

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Abstract

A forward genetics screen in mice identified a mutation in the gene Wdpcp that leads to severe skeletal dysmorphogenesis with disrupted formation of the primary cilium. The primary cilium is a transiently formed organelle that facilitates the processing of hedgehog transcription factors Gli2 and Gli3. Conditional deletion of Wdpcp in the limb bud mesenchyme recapitulates the appendicular skeletal phenotype of the constitutive Wdpcp loss of function mutant. Loss of Wdpcp disrupts formation of the repressor form of Gli3, leading to hyper activation of hedgehog pathway. This hyper activation delays chondrogenesis via increased expression of bone morphogenetic protein (BMP) inhibitor Grem1, suppressing activation of BMP pathway necessary for chondrogenesis. Suppression of hedgehog signaling and Grem1 expression and concomitant rescue of chondrogenesis is demonstrated with treatment of in vitro limb bud micromass cultures with direct hedgehog transcription factor Gli inhibitor GANT61, but not hedgehog signal transducer Smoothened inhibitor. This indicates that Wdpcp functions below Smoothened in the hedgehog pathway and directly implicates hedgehog signaling in the observed chondrogenic delay. In order to determine the effects of Wdpcp loss independent of this observed chondrogenic delay, we generated chondrocyte specific deletion mouse model of Wdpcp. Loss of Wdpcp and formation of the primary cilium in chondrocytes disrupts formation of trabecular bone, and mouse embryonic fibroblasts (MEFs) lacking Wdpcp have diminished in vitro osteogenesis. Activation of hedgehog pathway in MEFs lacking Wdpcp is rescued with lentiviral infection with a form of Gli2 mimicking amino terminal phosphorylation. We also demonstrate that overactivation of PKA in MEFs can restore disrupted formation of the repressor form of Gli3. These findings define an important role for Wdpcp and primary cilia in skeletal development and in coordinating the post-translational modification of Gli transcription factors necessary for normal hedgehog signaling.


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Details

Item Type: University of Pittsburgh ETD
Status: Published
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Langhans, Marklanghans.1@gmail.com0000-0002-2721-2834
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Tuan, Rockyrst13@pitt.eduRST13
Lo, Cecilia Wcel36@pitt.eduCEL36
Kwiatkowski, Adam Vadamkwi@pitt.eduADAMKWI
Davidson, Lance Alad43@pitt.eduLAD43
Tsang, Michaeltsang@pitt.eduTSANG
Date: 1 May 2015
Date Type: Publication
Defense Date: 14 April 2015
Approval Date: 1 May 2015
Submission Date: 1 May 2015
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 124
Institution: University of Pittsburgh
Schools and Programs: School of Medicine > Orthopaedic Surgery
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Wdpcp, cilia, hedgehog, skeletogenesis, differentiation, cartilage, bone
Date Deposited: 01 May 2015 17:22
Last Modified: 15 Nov 2016 14:28
URI: http://d-scholarship.pitt.edu/id/eprint/25105

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