@article {982, title = {TMEM218 dysfunction causes ciliopathies, including Joubert and Meckel syndromes.}, journal = {HGG Adv}, volume = {2}, year = {2021}, month = {2021 Jan 14}, abstract = {

The Joubert-Meckel syndrome spectrum is a continuum of recessive ciliopathy conditions caused by primary cilium dysfunction. The primary cilium is a microtubule-based, antenna-like organelle that projects from the surface of most human cell types, allowing them to respond to extracellular signals. The cilium is partitioned from the cell body by the transition zone, a known hotspot for ciliopathy-related proteins. Despite years of Joubert syndrome (JBTS) gene discovery, the genetic cause cannot be identified in up to 30\% of individuals with JBTS, depending on the cohort, sequencing method, and criteria for pathogenic variants. Using exome and targeted sequencing of 655 families with JBTS, we identified three individuals from two families harboring biallelic, rare, predicted-deleterious missense variants. Via MatchMaker Exchange, we identified biallelic variants in four additional families with ciliopathy phenotypes. Of note, four of the six families carry missense variants affecting the same highly conserved amino acid position 115. Clinical features included the molar tooth sign (N = 2), occipital encephalocele (N = 5, all fetuses), retinal dystrophy (N = 4, all living individuals), polycystic kidneys (N = 2), and polydactyly (N = 2), without liver involvement. Combined with existing functional data linking TMEM218 to ciliary transition zone function, our human genetic data make a strong case for TMEM218 dysfunction as a cause of ciliopathy phenotypes including JBTS with retinal dystrophy and Meckel syndrome. Identifying all genetic causes of the Joubert-Meckel spectrum enables diagnostic testing, prognostic and recurrence risk counseling, and medical monitoring, as well as work to delineate the underlying biological mechanisms and identify targets for future therapies.

}, issn = {2666-2477}, doi = {10.1016/j.xhgg.2020.100016}, author = {Van De Weghe, Julie C and Giordano, Jessica L and Mathijssen, Inge B and Mojarrad, Majid and Lugtenberg, Dorien and Miller, Caitlin V and Dempsey, Jennifer C and Mohajeri, Mahsa Sadat Asl and van Leeuwen, Elizabeth and Pajkrt, Eva and Klaver, Caroline C W and Houlden, Henry and Eslahi, Atieh and Waters, Aoife M and Bamshad, Michael J and Nickerson, Deborah A and Aggarwal, Vimla S and de Vries, Bert B A and Maroofian, Reza and Doherty, Dan} } @article {823, title = {Dysfunction of the ciliary ARMC9/TOGARAM1 protein module causes Joubert syndrome.}, journal = {J Clin Invest}, volume = {130}, year = {2020}, month = {2020 08 03}, pages = {4423-4439}, 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 = {Abnormalities, Multiple, Acetylation, Animals, Armadillo Domain Proteins, Cerebellum, Cilia, CRISPR-Cas Systems, Disease Models, Animal, Eye Abnormalities, Humans, Kidney Diseases, Cystic, Peptides, Retina, Zebrafish, Zebrafish Proteins}, issn = {1558-8238}, doi = {10.1172/JCI131656}, author = {Latour, Brooke L and Van De Weghe, Julie C and Rusterholz, Tamara Ds and Letteboer, Stef Jf and Gomez, Arianna and Shaheen, Ranad and Gesemann, Matthias and Karamzade, Arezou and Asadollahi, Mostafa and Barroso-Gil, Miguel and Chitre, Manali and Grout, Megan E and van Reeuwijk, Jeroen and van Beersum, Sylvia Ec and Miller, Caitlin V and Dempsey, Jennifer C and Morsy, Heba and Bamshad, Michael J and Nickerson, Deborah A and Neuhauss, Stephan Cf and Boldt, Karsten and Ueffing, Marius and Keramatipour, Mohammad and Sayer, John A and Alkuraya, Fowzan S and Bachmann-Gagescu, Ruxandra and Roepman, Ronald and Doherty, Dan} } @article {657, title = {GGC Repeat Expansion and Exon 1 Methylation of XYLT1 Is a Common Pathogenic Variant in Baratela-Scott Syndrome.}, journal = {Am J Hum Genet}, volume = {104}, year = {2019}, month = {2019 Jan 03}, pages = {35-44}, abstract = {

Baratela-Scott syndrome (BSS) is a rare, autosomal-recessive disorder characterized by short stature, facial dysmorphisms, developmental delay, and skeletal dysplasia caused by pathogenic variants in XYLT1. We report clinical and molecular investigation of 10 families (12 individuals) with BSS. Standard sequencing methods identified biallelic pathogenic variants in XYLT1 in only two families. Of the remaining cohort, two probands had no variants and six probands had only a single variant, including four with a heterozygous 3.1 Mb 16p13 deletion encompassing XYLT1 and two with a heterozygous truncating variant. Bisulfite sequencing revealed aberrant hypermethylation in exon 1 of XYLT1, always in trans with the sequence variant or deletion when present; both alleles were methylated in those with no identified variant. Expression of the methylated XYLT1 allele was severely reduced in fibroblasts from two probands. Southern blot studies combined with repeat expansion analysis of genome sequence data showed that the hypermethylation is associated with expansion of a GGC repeat in the XYLT1 promoter region that is not present in the reference genome, confirming that BSS is a trinucleotide repeat expansion disorder. The hypermethylated allele accounts for 50\% of disease alleles in our cohort and is not present in 130 control subjects. Our study highlights the importance of investigating non-sequence-based alterations, including epigenetic changes, to identify the missing heritability in genetic disorders.

}, issn = {1537-6605}, doi = {10.1016/j.ajhg.2018.11.005}, author = {LaCroix, Amy J and Stabley, Deborah and Sahraoui, Rebecca and Adam, Margaret P and Mehaffey, Michele and Kernan, Kelly and Myers, Candace T and Fagerstrom, Carrie and Anadiotis, George and Akkari, Yassmine M and Robbins, Katherine M and Gripp, Karen W and Baratela, Wagner A R and Bober, Michael B and Duker, Angela L and Doherty, Dan and Dempsey, Jennifer C and Miller, Daniel G and Kircher, Martin and Bamshad, Michael J and Nickerson, Deborah A and Mefford, Heather C and Sol-Church, Katia} } @article {555, title = {Rhombencephalosynapsis: Fused cerebellum, confused geneticists.}, journal = {Am J Med Genet C Semin Med Genet}, volume = {178}, year = {2018}, month = {2018 Dec}, pages = {432-439}, abstract = {

Rhombencephalosynapsis (RES) is a unique cerebellar malformation characterized by fusion of the cerebellar hemispheres with partial or complete absence of a recognizable cerebellar vermis. Subsets of patients also have other brain malformations such as midbrain fusion with aqueductal stenosis, characteristic craniofacial features (prominent forehead, flat midface, hypertelorism, ear abnormalities), and somatic malformations (heart, kidney, spine, and limb defects). Similar to known genetic brain malformations, the RES cerebellar malformation is highly stereotyped, yet no genetic causes have been identified. Here, we outline our current understanding of the genetic basis for RES, discuss limitations, and outline future approaches to identifying the causes of this fascinating brain malformation.

}, issn = {1552-4876}, doi = {10.1002/ajmg.c.31666}, author = {Aldinger, Kimberly A and Dempsey, Jennifer C and Tully, Hannah M and Grout, Megan E and Mehaffey, Michele G and Dobyns, William B and Doherty, Dan} } @article {392, title = {Mutations in ARMC9, which Encodes a Basal Body Protein, Cause Joubert Syndrome in Humans and Ciliopathy Phenotypes in Zebrafish.}, journal = {Am J Hum Genet}, volume = {101}, year = {2017}, month = {2017 Jul 06}, pages = {23-36}, abstract = {

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.

}, keywords = {Abnormalities, 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}, issn = {1537-6605}, doi = {10.1016/j.ajhg.2017.05.010}, author = {Van De Weghe, Julie C and Rusterholz, Tamara D S and Latour, Brooke and Grout, Megan E and Aldinger, Kimberly A and Shaheen, Ranad and Dempsey, Jennifer C and Maddirevula, Sateesh and Cheng, Yong-Han H and Phelps, Ian G and Gesemann, Matthias and Goel, Himanshu and Birk, Ohad S and Alanzi, Talal and Rawashdeh, Rifaat and Khan, Arif O and Bamshad, Michael J and Nickerson, Deborah A and Neuhauss, Stephan C F and Dobyns, William B and Alkuraya, Fowzan S and Roepman, Ronald and Bachmann-Gagescu, Ruxandra and Doherty, Dan} } @article {70, title = {Recessive Inactivating Mutations in TBCK, Encoding a Rab GTPase-Activating Protein, Cause Severe Infantile Syndromic Encephalopathy.}, journal = {Am J Hum Genet}, volume = {98}, year = {2016}, month = {2016 Apr 07}, pages = {772-81}, abstract = {

Infantile encephalopathies are a group of clinically and biologically heterogeneous disorders for which the genetic basis remains largely unknown. Here, we report a syndromic neonatal encephalopathy characterized by profound developmental disability, severe hypotonia, seizures, diminished respiratory drive requiring mechanical ventilation, brain atrophy, dysgenesis of the corpus callosum, cerebellar vermis hypoplasia, and facial dysmorphism. Biallelic inactivating mutations in TBCK (TBC1-domain-containing kinase) were independently identified by whole-exome sequencing as the cause of this condition in four unrelated families. Matching these families was facilitated by the sharing of phenotypic profiles and WES data in a recently released web-based tool (Geno2MP) that links phenotypic information to rare variants in families with Mendelian traits. TBCK is a putative GTPase-activating protein (GAP) for small GTPases of the Rab family and has been shown to control cell growth and proliferation, actin-cytoskeleton dynamics, and mTOR signaling. Two of the three mutations (c.376C>T [p.Arg126(*)] and c.1363A>T [p.Lys455(*)]) are predicted to truncate the protein, and loss of the major TBCK isoform was confirmed in primary fibroblasts from one affected individual. The third mutation, c.1532G>A (p.Arg511His), alters a conserved residue within the TBC1 domain. Structural analysis implicated Arg511 as a required residue for Rab-GAP function, and in~silico homology modeling predicted impaired GAP function in the corresponding mutant. These results suggest that loss of Rab-GAP activity is the underlying mechanism of disease. In contrast to other disorders caused by dysregulated mTOR signaling associated with focal or global brain overgrowth, impaired TBCK function results in progressive loss of brain volume.

}, keywords = {Adolescent, Alleles, Amino Acid Sequence, Brain Diseases, Child, Child, Preschool, Corpus Callosum, Female, GTPase-Activating Proteins, Humans, Magnetic Resonance Imaging, Male, Molecular Sequence Data, Mutation, Pedigree, Protein Conformation, Protein-Serine-Threonine Kinases, Signal Transduction, TOR Serine-Threonine Kinases}, issn = {1537-6605}, doi = {10.1016/j.ajhg.2016.01.016}, author = {Chong, Jessica X and Caputo, Viviana and Phelps, Ian G and Stella, Lorenzo and Worgan, Lisa and Dempsey, Jennifer C and Nguyen, Alina and Leuzzi, Vincenzo and Webster, Richard and Pizzuti, Antonio and Marvin, Colby T and Ishak, Gisele E and Ardern-Holmes, Simone and Richmond, Zara and Bamshad, Michael J and Ortiz-Gonzalez, Xilma R and Tartaglia, Marco and Chopra, Maya and Doherty, Dan} } @article {154, title = {KIAA0586 is Mutated in Joubert Syndrome.}, journal = {Hum Mutat}, volume = {36}, year = {2015}, month = {2015 Sep}, pages = {831-5}, abstract = {

Joubert syndrome (JS) is a recessive neurodevelopmental disorder characterized by a distinctive mid-hindbrain malformation. JS is part of a group of disorders called ciliopathies based on their overlapping phenotypes and common underlying pathophysiology linked to primary cilium dysfunction. Biallelic mutations in one of 28 genes, all encoding proteins localizing to the primary cilium or basal body, can cause JS. Despite this large number of genes, the genetic cause can currently be determined in about 62\% of individuals with JS. To identify novel JS genes, we performed whole exome sequencing on 35 individuals with JS and found biallelic rare deleterious variants (RDVs) in KIAA0586, encoding a centrosomal protein required for ciliogenesis, in one individual. Targeted next-generation sequencing in a large JS cohort identified biallelic RDVs in eight additional families for an estimated prevalence of 2.5\% (9/366 JS families). All affected individuals displayed JS phenotypes toward the mild end of the spectrum.

}, keywords = {Abnormalities, Multiple, Adolescent, Adult, Alternative Splicing, Brain, Cell Cycle Proteins, Cerebellum, Child, Child, Preschool, DNA Mutational Analysis, Eye Abnormalities, Gene Order, Genetic Association Studies, Humans, Kidney Diseases, Cystic, Magnetic Resonance Imaging, Mutation, Phenotype, Retina, Young Adult}, issn = {1098-1004}, doi = {10.1002/humu.22821}, author = {Bachmann-Gagescu, Ruxandra and Phelps, Ian G and Dempsey, Jennifer C and Sharma, Vivek A and Ishak, Gisele E and Boyle, Evan A and Wilson, Meredith and Marques Louren{\c c}o, Charles and Arslan, Mutluay and Shendure, Jay and Doherty, Dan} } @article {228, title = {Mutations in LAMA1 cause cerebellar dysplasia and cysts with and without retinal dystrophy.}, journal = {Am J Hum Genet}, volume = {95}, year = {2014}, month = {2014 Aug 07}, pages = {227-34}, abstract = {

Cerebellar dysplasia with cysts (CDC) is an imaging finding typically seen in combination with cobblestone cortex and congenital muscular dystrophy in individuals with dystroglycanopathies. More recently, CDC was reported in seven children without neuromuscular involvement (Poretti-Boltshauser syndrome). Using a combination of homozygosity mapping and whole-exome sequencing, we identified biallelic mutations in LAMA1 as the cause of CDC in seven affected individuals (from five families) independent from those included in the phenotypic description of Poretti-Boltshauser syndrome. Most of these individuals also have high myopia, and some have retinal dystrophy and patchy increased T2-weighted fluid-attenuated inversion recovery (T2/FLAIR) signal in cortical white matter. In one additional family, we identified two siblings who have truncating LAMA1 mutations in combination with retinal dystrophy and mild cerebellar dysplasia without cysts, indicating that cysts are not an obligate feature associated with loss of LAMA1 function. This work expands the phenotypic spectrum associated with the lamininopathy disorders and highlights the tissue-specific roles played by different laminin-encoding genes.

}, keywords = {Adult, Alleles, Base Sequence, Cerebellar Cortex, Cerebellar Diseases, Child, Child, Preschool, Cysts, Exome, Female, Humans, Laminin, Male, Muscular Dystrophies, Retinal Dystrophies, Sequence Analysis, DNA, Young Adult}, issn = {1537-6605}, doi = {10.1016/j.ajhg.2014.07.007}, author = {Aldinger, Kimberly A and Mosca, Stephen J and T{\'e}treault, Martine and Dempsey, Jennifer C and Ishak, Gisele E and Hartley, Taila and Phelps, Ian G and Lamont, Ryan E and O{\textquoteright}Day, Diana R and Basel, Donald and Gripp, Karen W and Baker, Laura and Stephan, Mark J and Bernier, Francois P and Boycott, Kym M and Majewski, Jacek and Parboosingh, Jillian S and Innes, A Micheil and Doherty, Dan} }