RESUMEN
Better methods are required to interpret the pathogenicity of disease-associated variants of uncertain significance (VUS), which cannot be actioned clinically. In this study, we explore the use of an animal model (Caenorhabditis elegans) for in vivo interpretation of missense VUS alleles of TMEM67, a cilia gene associated with ciliopathies. CRISPR/Cas9 gene editing was used to generate homozygous knock-in C. elegans worm strains carrying TMEM67 patient variants engineered into the orthologous gene (mks-3). Quantitative phenotypic assays of sensory cilia structure and function (neuronal dye filling, roaming and chemotaxis assays) measured how the variants impacted mks-3 gene function. Effects of the variants on mks-3 function were further investigated by looking at MKS-3::GFP localization and cilia ultrastructure. The quantitative assays in C. elegans accurately distinguished between known benign (Asp359Glu, Thr360Ala) and known pathogenic (Glu361Ter, Gln376Pro) variants. Analysis of eight missense VUS generated evidence that three are benign (Cys173Arg, Thr176Ile and Gly979Arg) and five are pathogenic (Cys170Tyr, His782Arg, Gly786Glu, His790Arg and Ser961Tyr). Results from worms were validated by a genetic complementation assay in a human TMEM67 knock-out hTERT-RPE1 cell line that tests a TMEM67 signalling function. We conclude that efficient genome editing and quantitative functional assays in C. elegans make it a tractable in vivo animal model for rapid, cost-effective interpretation of ciliopathy-associated missense VUS alleles.
Asunto(s)
Proteínas de Caenorhabditis elegans , Ciliopatías , Animales , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Cilios/genética , Cilios/metabolismo , Ciliopatías/metabolismo , Edición Génica , Humanos , Mutación Missense/genéticaRESUMEN
Age-related macular degeneration (AMD) is a leading cause of blindness among the elderly. Canonical disease models suggest that defective interactions between complement factor H (CFH) and cell surface heparan sulfate (HS) result in increased alternative complement pathway activity, cytolytic damage, and tissue inflammation in the retina. Although these factors are thought to contribute to increased disease risk, multiple studies indicate that noncanonical mechanisms that result from defective CFH and HS interaction may contribute to the progression of AMD as well. A total of 60 ciliated sensory neurons in the nematode Caenorhabditis elegans detect chemical, olfactory, mechanical, and thermal cues in the environment. Here, we find that a C. elegans CFH homolog localizes on CEP mechanosensory neuron cilia where it has noncanonical roles in maintaining inversin/NPHP-2 within its namesake proximal compartment and preventing inversin/NPHP-2 accumulation in distal cilia compartments in aging adults. CFH localization and maintenance of inversin/NPHP-2 compartment integrity depend on the HS 3-O sulfotransferase HST-3.1 and the transmembrane proteoglycan syndecan/SDN-1. Defective inversin/NPHP-2 localization in mouse and human photoreceptors with CFH mutations indicates that these functions and interactions may be conserved in vertebrate sensory neurons, suggesting that previously unappreciated defects in cilia structure may contribute to the progressive photoreceptor dysfunction associated with CFH loss-of-function mutations in some AMD patients.
Asunto(s)
Factor H de Complemento/metabolismo , Heparitina Sulfato/metabolismo , Retina/metabolismo , Animales , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/metabolismo , Cilios/metabolismo , Factor H de Complemento/fisiología , Heparitina Sulfato/fisiología , Degeneración Macular/metabolismo , Degeneración Macular/fisiopatología , Neuronas/metabolismo , Factores de Transcripción/metabolismoRESUMEN
Ciliopathies are inherited disorders caused by defects in motile and non-motile (primary) cilia. Ciliopathy syndromes and associated gene variants are often highly pleiotropic and represent exemplars for interrogating genotype-phenotype correlations. Towards understanding disease mechanisms in the context of ciliopathy mutations, we have used a leading model organism for cilia and ciliopathy research, Caenorhabditis elegans, together with gene editing, to characterise two missense variants (P74S and G155S) in mksr-2/B9D2 associated with Joubert syndrome (JBTS). B9D2 functions within the Meckel syndrome (MKS) module at the ciliary base transition zone (TZ) compartment and regulates the molecular composition and sensory/signalling functions of the cilium. Quantitative assays of cilium/TZ structure and function, together with knock-in reporters, confirm that both variant alleles are pathogenic in worms. G155S causes a more severe overall phenotype and disrupts endogenous MKSR-2 organisation at the TZ. Recapitulation of the patient biallelic genotype shows that compound heterozygous worms phenocopy worms homozygous for P74S. The P74S and G155S alleles also reveal evidence of a very close functional association between the B9D2-associated B9 complex and MKS-2/TMEM216. Together, these data establish C. elegans as a model for interpreting JBTS mutations and provide further insight into MKS module organisation. This article has an associated First Person interview with the first author of the paper.
Asunto(s)
Anomalías Múltiples/genética , Caenorhabditis elegans/genética , Cerebelo/anomalías , Cilios/metabolismo , Anomalías del Ojo/genética , Enfermedades Renales Quísticas/genética , Mutación Missense , Retina/anomalías , Anomalías Múltiples/fisiopatología , Alelos , Animales , Sistemas CRISPR-Cas , Proteínas de Caenorhabditis elegans/metabolismo , Cerebelo/fisiopatología , Modelos Animales de Enfermedad , Anomalías del Ojo/fisiopatología , Edición Génica , Estudios de Asociación Genética , Genotipo , Humanos , Enfermedades Renales Quísticas/fisiopatología , Proteínas de la Membrana/metabolismo , Mutación , Fenotipo , Retina/fisiopatologíaRESUMEN
During mitosis, kinetochore-microtubule interactions ensure that chromosomes are accurately segregated to daughter cells. RSA-1 (regulator of spindle assembly-1) is a regulatory Bâ³ subunit of protein phosphatase 2A that was previously proposed to modulate microtubule dynamics during spindle assembly. We have identified a genetic interaction between the centrosomal protein, RSA-1, and the spindle- and kinetochore-associated (Ska) complex in Caenorhabditis elegans In a forward genetic screen for suppressors of rsa-1(or598) embryonic lethality, we identified mutations in ska-1 and ska-3 Loss of SKA-1 and SKA-3, as well as components of the KMN (KNL-1/MIS-12/NDC-80) complex and the microtubule end-binding protein EBP-2, all suppressed the embryonic lethality of rsa-1(or598) These suppressors also disrupted the intracellular localization of the Ska complex, revealing a network of proteins that influence Ska function during mitosis. In rsa-1(or598) embryos, SKA-1 is excessively and prematurely recruited to kinetochores during spindle assembly, but SKA-1 levels return to normal just prior to anaphase onset. Loss of the TPX2 homolog, TPXL-1, also resulted in overrecruitment of SKA-1 to the kinetochores and this correlated with the loss of Aurora A kinase on the spindle microtubules. We propose that rsa-1 regulates the kinetochore localization of the Ska complex, with spindle-associated Aurora A acting as a potential mediator. These data reveal a novel mechanism of protein phosphatase 2A function during mitosis involving a centrosome-based regulatory mechanism for Ska complex recruitment to the kinetochore.
Asunto(s)
Proteínas de Caenorhabditis elegans/genética , Proteínas Cromosómicas no Histona/genética , Cinetocoros/metabolismo , Microtúbulos/metabolismo , Proteína Fosfatasa 2/genética , Huso Acromático/metabolismo , Anafase/genética , Animales , Aurora Quinasa A/metabolismo , Caenorhabditis elegans/embriología , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas Portadoras/metabolismo , Centrosoma/metabolismo , Proteínas Cromosómicas no Histona/metabolismo , Segregación Cromosómica/genética , Cinesinas/metabolismo , Proteínas de Microtúbulos/metabolismo , Proteínas Asociadas a Microtúbulos/metabolismo , Mitosis/genética , Proteína Fosfatasa 2/metabolismoRESUMEN
Protein phosphatase 2A (PP2A) is a heterotrimer composed of single catalytic and scaffolding subunits and one of several possible regulatory subunits. We identified PPTR-2, a regulatory subunit of PP2A, as a binding partner for the giant muscle protein UNC-89 (obscurin) in Caenorhabditis elegans. PPTR-2 is required for sarcomere organization when its paralogue, PPTR-1, is deficient. PPTR-2 localizes to the sarcomere at dense bodies and M-lines, colocalizing with UNC-89 at M-lines. PP2A components in C. elegans include one catalytic subunit LET-92, one scaffolding subunit (PAA-1), and five regulatory subunits (SUR-6, PPTR-1, PPTR-2, RSA-1, and CASH-1). In adult muscle, loss of function in any of these subunits results in sarcomere disorganization. rsa-1 mutants show an interesting phenotype: one of the two myosin heavy chains, MHC A, localizes as closely spaced double lines rather than single lines. This "double line" phenotype is found in rare missense mutants of the head domain of MHC B myosin, such as unc-54(s74). Analysis of phosphoproteins in the unc-54(s74) mutant revealed two additional phosphoserines in the nonhelical tailpiece of MHC A. Antibodies localize PPTR-1, PAA-1, and SUR-6 to I-bands and RSA-1 to M-lines and I-bands. Therefore, PP2A localizes to sarcomeres and functions in the assembly or maintenance of sarcomeres.
Asunto(s)
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/enzimología , Músculo Estriado/enzimología , Proteína Fosfatasa 2/metabolismo , Sarcómeros/metabolismo , Animales , Mutación Missense/genética , Fenotipo , Fosforilación , Unión Proteica , Mapeo de Interacción de Proteínas , Subunidades de Proteína/metabolismo , Proteínas Recombinantes/metabolismo , Técnicas del Sistema de Dos HíbridosRESUMEN
BACKGROUND: Cervical carotid dissection is more common in extracranical vessel: internal carotid artery dissection (ICAD) is typical, vertebral artery dissection is uncommon, common carotid artery dissection (CCAD) is rare and even a more rare cause of ischemic stroke. Cervical artery dissections account up to 20-25% of ischemic strokes in young patients. Isolated and spontaneous common carotid artery dissection without aortic damage is unique. Indeed in the Literature 8 cases were identified. MRI and CTA were the most commonly used for diagnosis and follow-up. CASE REPORT: A 67-year-old came to our observation reporting burning pain in the right latero-cervical region in supine position, irradiated in the temporal region and recurrent episodes of migraine with aura (scintillating scotoma), in the last 3 months. The last Doppler Ultrasound control, performed after the onset of symptoms, showed an highlighted dissection wall with double lumen at the origin of the bulb and the internal carotid artery on the right. Aortic arch arteriography confirmed the diagnosis. The patient underwent surgery (longitudinal arteriotomy, removing four miointimal flaps, fastening the distal common carotid artery with 3 Kunlin's points). RESULTS: Any neurological or vascular problems after surgery were noticed. DISCUSSION AND COMMENTS: The pathogenesis can be related to a combination of an intrinsic weakness in the arterial wall and an external trigger. The diagnosis of CAD is made with MRI (78.0%), conventional angiography (31.1%), CTA (14.7%), and ultrasound (11.3%). CONCLUSION: No evidence-based guidelines exists for treatment of CCAD. In our patient surgical CEA treatment was the optimal solution.
Asunto(s)
Enfermedades de las Arterias Carótidas/cirugía , Anciano , Femenino , HumanosRESUMEN
Protein phosphorylation and dephosphorylation is a key mechanism for the spatial and temporal regulation of many essential developmental processes and is especially prominent during mitosis. The multi-subunit protein phosphatase 2A (PP2A) enzyme plays an important, yet poorly characterized role in dephosphorylating proteins during mitosis. PP2As are heterotrimeric complexes comprising a catalytic, structural, and regulatory subunit. Regulatory subunits are mutually exclusive and determine subcellular localization and substrate specificity of PP2A. At least 3 different classes of regulatory subunits exist (termed B, B', Bâ³) but there is no obvious similarity in primary sequence between these classes. Therefore, it is not known how these diverse regulatory subunits interact with the same holoenzyme to facilitate specific PP2A functions in vivo. The Bâ³ family of regulatory subunits is the least understood because these proteins lack conserved structural domains. RSA-1 (regulator of spindle assembly) is a regulatory Bâ³ subunit required for mitotic spindle assembly in Caenorhabditis elegans. In order to address how Bâ³ subunits interact with the PP2A core enzyme, we focused on a conditional allele, rsa-1(or598ts), and determined that this mutation specifically disrupts the protein interaction between RSA-1 and the PP2A structural subunit, PAA-1. Through genetic screening, we identified a putative interface on the PAA-1 structural subunit that interacts with a defined region of RSA-1/Bâ³. In the context of previously published results, these data propose a mechanism of how different PP2A B-regulatory subunit families can bind the same holoenzyme in a mutually exclusive manner, to perform specific tasks in vivo.
RESUMEN
As part of a multi-subunit ring complex, γ-tubulin has been shown to promote microtubule nucleation both in vitro and in vivo, and the structural properties of the complex suggest that it also seals the minus ends of the polymers with a conical cap. Cells depleted of γ-tubulin, however, still display many microtubules that participate in mitotic spindle assembly, suggesting that γ-tubulin is not absolutely required for microtubule nucleation in vivo, and raising questions about the function of the minus end cap. Here, we assessed the role of γ-tubulin in centrosomal microtubule organisation using three-dimensional reconstructions of γ-tubulin-depleted C. elegans embryos. We found that microtubule minus-end capping and the PCM component SPD-5 are both essential for the proper placement of microtubules in the centrosome. Our results further suggest that γ-tubulin and SPD-5 limit microtubule polymerization within the centrosome core, and we propose a model for how abnormal microtubule organization at the centrosome could indirectly affect centriole structure and daughter centriole replication.