Mutations in ARMC9, which Encodes a Basal Body Protein, Cause Joubert Syndrome in Humans and Ciliopathy Phenotypes in Zebrafish.

TitleMutations in ARMC9, which Encodes a Basal Body Protein, Cause Joubert Syndrome in Humans and Ciliopathy Phenotypes in Zebrafish.
Publication TypeJournal Article
Year of Publication2017
AuthorsVan De Weghe, JC, Rusterholz, TDS, Latour, B, Grout, ME, Aldinger, KA, Shaheen, R, Dempsey, JC, Maddirevula, S, Cheng, Y-HH, Phelps, IG, Gesemann, M, Goel, H, Birk, OS, Alanzi, T, Rawashdeh, R, Khan, AO, Bamshad, MJ, Nickerson, DA, Neuhauss, SCF, Dobyns, WB, Alkuraya, FS, Roepman, R, Bachmann-Gagescu, R, Doherty, D
Corporate AuthorsUniversity of Washington Center for Mendelian Genomics
JournalAm J Hum Genet
Date Published2017 Jul 06
KeywordsAbnormalities, Multiple, Animals, Armadillo Domain Proteins, Basal Bodies, Base Sequence, Brain, Cerebellum, Cilia, Ciliopathies, Diagnostic Imaging, Exome, Eye Abnormalities, Genetic Predisposition to Disease, Humans, Kidney Diseases, Cystic, Mutation, Phenotype, Retina, Sequence Analysis, DNA, Up-Regulation, Zebrafish, Zebrafish Proteins

Joubert syndrome (JS) is a recessive neurodevelopmental disorder characterized by hypotonia, ataxia, abnormal eye movements, and variable cognitive impairment. It is defined by a distinctive brain malformation known as the "molar tooth sign" on axial MRI. Subsets of affected individuals have malformations such as coloboma, polydactyly, and encephalocele, as well as progressive retinal dystrophy, fibrocystic kidney disease, and liver fibrosis. More than 35 genes have been associated with JS, but in a subset of families the genetic cause remains unknown. All of the gene products localize in and around the primary cilium, making JS a canonical ciliopathy. Ciliopathies are unified by their overlapping clinical features and underlying mechanisms involving ciliary dysfunction. In this work, we identify biallelic rare, predicted-deleterious ARMC9 variants (stop-gain, missense, splice-site, and single-exon deletion) in 11 individuals with JS from 8 families, accounting for approximately 1% of the disorder. The associated phenotypes range from isolated neurological involvement to JS with retinal dystrophy, additional brain abnormalities (e.g., heterotopia, Dandy-Walker malformation), pituitary insufficiency, and/or synpolydactyly. We show that ARMC9 localizes to the basal body of the cilium and is upregulated during ciliogenesis. Typical ciliopathy phenotypes (curved body shape, retinal dystrophy, coloboma, and decreased cilia) in a CRISPR/Cas9-engineered zebrafish mutant model provide additional support for ARMC9 as a ciliopathy-associated gene. Identifying ARMC9 mutations as a cause of JS takes us one step closer to a full genetic understanding of this important disorder and enables future functional work to define the central biological mechanisms underlying JS and other ciliopathies.

Alternate JournalAm. J. Hum. Genet.
PubMed ID28625504
PubMed Central IDPMC5501774
Grant ListU54 HG006493 / HG / NHGRI NIH HHS / United States
U54 HD083091 / HD / NICHD NIH HHS / United States
R01 NS050375 / NS / NINDS NIH HHS / United States
UM1 HG006493 / HG / NHGRI NIH HHS / United States
R01 NS064077 / NS / NINDS NIH HHS / United States