Dysfunction of the ciliary ARMC9/TOGARAM1 protein module causes Joubert syndrome

J Clin Invest. 2020 Aug 3;130(8):4423-4439. doi: 10.1172/JCI131656.

Brooke L Latour ¹, Julie C Van De Weghe ², Tamara Ds Rusterholz ³ ⁴, Stef Jf Letteboer ¹, Arianna Gomez ², Ranad Shaheen ⁵, Matthias Gesemann ⁴, Arezou Karamzade ⁶, Mostafa Asadollahi ⁶, Miguel Barroso-Gil ⁷, Manali Chitre ⁸, Megan E Grout ², Jeroen van Reeuwijk ¹, Sylvia Ec van Beersum ¹, Caitlin V Miller ², Jennifer C Dempsey ², Heba Morsy ⁹, University of Washington Center for Mendelian Genomics, Michael J Bamshad ² ¹⁰ ¹¹ ¹², Genomics England Research Consortium, Deborah A Nickerson ¹⁰ ¹¹, Stephan Cf Neuhauss ⁴, Karsten Boldt ¹³, Marius Ueffing ¹³, Mohammad Keramatipour ⁶, John A Sayer ⁷, Fowzan S Alkuraya ⁵ ¹⁴, Ruxandra Bachmann-Gagescu ³ ⁴, Ronald Roepman ¹, Dan Doherty ² ¹⁵

Affiliations

1 Department of Human Genetics and Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands.
2 Department of Pediatrics, University of Washington, Seattle, Washington, USA.
3 Institute of Medical Genetics, and.
4 Department of Molecular Life Sciences, University of Zurich, Zürich, Switzerland.
5 Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.
6 Department of Medical Genetics, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
7 Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, United Kingdom.
8 Department of Paediatric Neurology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom.
9 Department of Human Genetics, Medical Research Institute, Alexandria University, Alexandria, Egypt.
10 The University of Washington Center for Mendelian Genomics is detailed in Supplemental Acknowledgments.
11 University of Washington Center for Mendelian Genomics, Seattle, Washington, USA.
12 Department of Genome Sciences, University of Washington, Seattle, Washington, USA.
13 Medical Proteome Center, Institute for Ophthalmic Research, University of Tuebingen, Tuebingen, Germany.
14 Department of Anatomy and Cell Biology, College of Medicine, Alfaisal University, Riyadh, Saudi Arabia.
15 Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, USA.

PMID: 32453716 DOI: 10.1172/JCI131656

Abstract

Joubert syndrome (JBTS) is a recessive neurodevelopmental ciliopathy characterized by a pathognomonic hindbrain malformation. All known JBTS genes encode proteins involved in the structure or function of primary cilia, ubiquitous antenna-like organelles essential for cellular signal transduction. Here, we used the recently identified JBTS-associated protein armadillo repeat motif-containing 9 (ARMC9) in tandem-affinity purification and yeast 2-hybrid screens to identify a ciliary module whose dysfunction underlies JBTS. In addition to the known JBTS-associated proteins CEP104 and CSPP1, we identified coiled-coil domain containing 66 (CCDC66) and TOG array regulator of axonemal microtubules 1 (TOGARAM1) as ARMC9 interaction partners. We found that TOGARAM1 variants cause JBTS and disrupt TOGARAM1 interaction with ARMC9. Using a combination of protein interaction analyses, characterization of patient-derived fibroblasts, and analysis of CRISPR/Cas9-engineered zebrafish and hTERT-RPE1 cells, we demonstrated that dysfunction of ARMC9 or TOGARAM1 resulted in short cilia with decreased axonemal acetylation and polyglutamylation, but relatively intact transition zone function. Aberrant serum-induced ciliary resorption and cold-induced depolymerization in ARMC9 and TOGARAM1 patient cell lines suggest a role for this new JBTS-associated protein module in ciliary stability.

Keywords

Genetic diseases; Genetics; Proteomics.

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