Dysfunction of the ciliary ARMC9/TOGARAM1 protein module causes Joubert syndrome
Brooke L. Latour, … , Ronald Roepman, Dan Doherty
Brooke L. Latour, … , Ronald Roepman, Dan Doherty
Published May 26, 2020
Citation Information: J Clin Invest. 2020;130(8):4423-4439. https://doi.org/10.1172/JCI131656.
View: Text | PDF
Research Article Genetics

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

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.

Authors

Brooke L. Latour, Julie C. Van De Weghe, Tamara D.S. Rusterholz, Stef J.F. Letteboer, Arianna Gomez, Ranad Shaheen, Matthias Gesemann, Arezou Karamzade, Mostafa Asadollahi, Miguel Barroso-Gil, Manali Chitre, Megan E. Grout, Jeroen van Reeuwijk, Sylvia E.C. van Beersum, Caitlin V. Miller, Jennifer C. Dempsey, Heba Morsy, University of Washington Center for Mendelian Genomics, Michael J. Bamshad, Genomics England Research Consortium, Deborah A. Nickerson, Stephan C.F. Neuhauss, Karsten Boldt, Marius Ueffing, Mohammad Keramatipour, John A. Sayer, Fowzan S. Alkuraya, Ruxandra Bachmann-Gagescu, Ronald Roepman, Dan Doherty

×

Figure 2

TOGARAM1 variants cause JBTS.

Options: View larger image (or click on image) Download as PowerPoint
TOGARAM1 variants cause JBTS. (A) Pedigrees and segregation of TOGARAM1...
(A) Pedigrees and segregation of TOGARAM1 variants. (B) Brain imaging features in individuals with TOGARAM1-related JBTS. MTS (arrowheads in left column, axial T2-weighted images) and elevated roof of the fourth ventricle (arrows in right column, sagittal T1-weighted [top 2] and T2-weighted [bottom] images). Much of the cerebellar tissue on the sagittal images (right panels) is hemisphere, based on axial and coronal views (not shown). (C) Multi-exon deletion in UW360. Primers flanking the predicted deletion amplify a 1064-bp product in the father (F) and the affected son (S) due to a 12,191-bp deletion, but not in the mother (M), because the predicted product was too large. Sanger sequencing of the breakpoint in gDNA (upper) and cDNA (lower) from the affected child confirmed the deletion of exons 4–7. Coding genomic schematic of Homo sapiens TOGARAM1. Transcript variant 1 is shown (NM_001308120.2; variant 2 NM_015091.4, not shown). (D) Protein schematic of TOGARAM1 with JBTS-associated variants indicated. TOG domains 1–4 are shown, with HEAT repeats indicated in gradients of blue.