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Pazour, G. J.

Publications and source records attributed to Pazour, G. J..

2 recordsLinked to original sources
bioRxiv2017

Uncoupling Intraflagellar Transport and Primary Cilia Formation Demonstrates Deep Integration of IFT in Hedgehog Signaling

The vertebrate hedgehog pathway is organized in primary cilia and hedgehog components relocate into or out of cilia during signaling. Defects in intraflagellar transport (IFT) typically disrupt ciliary assembly and attenuate hedgehog signaling. Determining if IFT drives the movement of hedgehog components is difficult due to the requirement of IFT for building cilia. Unlike most IFT proteins, IFT27 is dispensable for cilia formation but affects hedgehog signaling similar to other IFTs allowing us to examine its role in the dynamics of signaling. Activating signaling at points along the pathway in Ift27 mutant cells showed that IFT is extensively involved in the pathway. Similar analysis of Bbs mutant cells showed that BBS proteins participate at many levels of signaling but are not needed to concentrate Gli transcription factors at the ciliary tip. Our analysis showed that smoothened delivery to cilia does not require IFT27, but the role of other IFTs is not known. Using a rapamycin-induced dimerization system to stop IFT after ciliary assembly was complete we show that smoothened delivery to cilia is IFT independent.\n\nAbbreviations

cell biology↗
bioRxiv2017

Super-Resolution Microscopy Reveals That Disruption Of Ciliary Transition Zone Architecture Is A Cause Of Joubert Syndrome

Diverse human ciliopathies, including nephronophthisis (NPHP), Meckel syndrome (MKS) and Joubert syndrome (JBTS), can be caused by mutations affecting components of the transition zone, a ciliary domain near its base. The transition zone controls the protein composition of the ciliary membrane, but how it does so is unclear. To better understand the transition zone and its connection to ciliopathies, we defined the arrangement of key proteins in the transition zone using two-color stochastic optical reconstruction microscopy (STORM). This mapping revealed that NPHP and MKS complex components form nested rings comprised of nine-fold doublets. The NPHP complex component RPGRIP1L forms a smaller diameter transition zone ring within the MKS complex rings. JBTS-associated mutations in RPGRIP1L disrupt the architecture of the MKS and NPHP rings, revealing that vertebrate RPGRIP1L has a key role in organizing transition zone architecture. JBTS-associated mutations in TCTN2, encoding an MKS complex component, also displace proteins of the MKS and NPHP complexes from the transition zone, revealing that RPGRIP1L and TCTN2 have interdependent roles in organizing transition zone architecture. To understand how altered transition zone architecture affects developmental signaling, we examined the localization of the Hedgehog pathway component SMO in human fibroblasts derived from JBTS-affected individuals. We found that diverse ciliary proteins, including SMO, accumulate at the transition zone in wild type cells, suggesting that the transition zone is a way station for proteins entering and exiting the cilium. JBTS-associated mutations in RPGRIP1L disrupt SMO accumulation at the transition zone and the ciliary localization of SMO. We propose that the disruption of transition zone architecture in JBTS leads to a failure of SMO to accumulate at the transition zone, disrupting developmental signaling in JBTS.

cell biology↗