EFHC1, Implicated in Juvenile Myoclonic Epilepsy, Functions at the Cilium and Synapse to Modulate Dopamine Signaling

Neurons throughout the mammalian brain possess non-motile cilia, organelles with varied functions in sensory physiology and cellular signaling. Yet, the roles of cilia in these neurons are poorly understood. To shed light into their functions, we studied EFHC1, an evolutionarily conserved protein required for motile cilia function and linked to a common form of inherited epilepsy in humans, juvenile myoclonic epilepsy (JME). We demonstrate that C. elegans EFHC-1 functions within specialized non-motile mechanosensory cilia, where it regulates neuronal activation and dopamine signaling. EFHC-1 also localizes at the synapse, where it further modulates dopamine signaling in cooperation with the orthologue of an R-type voltage-gated calcium channel. Our findings unveil a previously undescribed dual-regulation of neuronal excitability at sites of neuronal sensory input (cilium) and neuronal output (synapse). Such a distributed regulatory mechanism may be essential for establishing neuronal activation thresholds under physiological conditions, and when impaired, may represent a novel pathomechanism for epilepsy

Unraveling the genetic complexity of ciliopathies in the Hutterite population

Bibliography: p. 88-93Some pages are in colour.Includes copy of ethics approval. Original copy with original Partial Copyright Licence.Ciliopathies are a group of genetically heterogeneous disorders with overlapping clinical manifestations and causative genes localizing to the nonmotile cilium. Many ciliopathies are present in the genetically isolated Hutterite population. This work was initiated to identify the remaining unknown ciliopathy mutations within the population, and four additional ciliopathy mutations were found. Some Hutterite nephronophthisis patients were compound heterozygous for a c.1918delA variant in NP HP 1 and the common NP HP 1 deletion, and one patient without NP HP 1 mutations was homozygous for a c.3936_3937insAC variant in KIAAJ009. Cranioectodermal dysplasia patients in the Hutterites were homozygous for a c.17T>A variant in DPHJ, and Joubert syndrome related disorder patients without homozygous TMEM237 mutations were homozygous for a c.363 _364delT A variant in CSP P 1. Identifying the causative mutations for ciliopathies in the Hutterites allows for diagnostic testing within the population and furthers our understanding of the complexity of ciliopathies in both the Hutterites and the general populatio

Dissecting the sensory roles of motility-associated ciliary genes in Caenorhabditis elegans

Cilia are microtubule-based organelles that emanate from the surface of most mammalian cell types. Motile cilia have well known roles in producing flow, while non-motile cilia play important sensory/signalling roles. Both forms are based on a similar axonemal structure, but ciliary motility requires additional components that conform to a regular arrangement along microtubules thought to be dictated by the protofilament ribbon (pf-ribbon). While pf-ribbon proteins have been implicated in ciliary motility, sensory/signalling functions in non-motile cilia have been less apparent. Although the ciliated organism Caenorhabditis elegans lacks motile cilia, orthologues of several ciliary pf-ribbon-associated proteins are present, including PACRG (Parkin co-regulated gene) and EFHC1 (EF-hand containing 1). In addition to their localisation to motile cilia, the pf-ribbon proteins show expression in neuronal cells of the brain where they may play important sensory roles. In particular, EFHC1 is mutated in the most common form of inherited epilepsy in humans and has been shown to be important for proper neuronal communication. This work investigates these motility-associated genes in C. elegans to dissect their sensory/signalling roles. We find that both PCRG-1 and EFHC-1 localise to a small subset of non-motile cilia in C. elegans, suggesting that they have been adapted to mediate specific sensory/signalling functions. We show that PCRG-1 influences a learning behaviour known as gustatory plasticity, where it is functionally coupled to heterotrimeric G-protein signalling. We also demonstrate that PCRG-1 promotes longevity in C. elegans by acting upstream of the lifespan-promoting FOXO transcription factor DAF-16 and likely upstream of insulin/IGF signalling, and that EFHC-1 also promotes longevity, suggesting shared signalling functions for these proteins. In addition, EFHC-1 modulates dopamine signalling where it is required for ciliary mechanosensation and regulating synaptic release of dopamine in cooperation with a voltage-gated calcium channel. Our findings establish previously unrecognised sensory/signalling functions for both PACRG and EFHC1 that may be important for neuronal communication in the human brain, where both proteins are known to be present. Furthermore, our work provides important clues for understanding and ultimately providing novel avenues for intervention of disorders such as epilepsy

The myelin water imaging transcriptome: myelin water fraction regionally varies with oligodendrocyte-specific gene expression

Abstract Identifying sensitive and specific measures that can quantify myelin are instrumental in characterizing microstructural changes in neurological conditions. Neuroimaging transcriptomics is emerging as a valuable technique in this regard, offering insights into the molecular basis of promising candidates for myelin quantification, such as myelin water fraction (MWF). We aimed to demonstrate the utility of neuroimaging transcriptomics by validating MWF as a myelin measure. We utilized data from a normative MWF brain atlas, comprised of 50 healthy subjects (mean age = 25 years, range = 17–42 years) scanned at 3 Tesla. Magnetic resonance imaging data included myelin water imaging to extract MWF and T1 anatomical scans for image registration and segmentation. We investigated the inter-regional distributions of gene expression data from the Allen Human Brain Atlas in conjunction with inter-regional MWF distribution patterns. Pearson correlations were used to identify genes with expression profiles mirroring MWF. The Single Cell Type Atlas from the Human Protein Atlas was leveraged to classify genes into gene sets with high cell type specificity, and a control gene set with low cell type specificity. Then, we compared the Pearson correlation coefficients for each gene set to determine if cell type-specific gene expression signatures correlate with MWF. Pearson correlation coefficients between MWF and gene expression for oligodendrocytes and adipocytes were significantly higher than for the control gene set, whereas correlations between MWF and inhibitory/excitatory neurons were significantly lower. Our approach in integrating transcriptomics with neuroimaging measures supports an emerging technique for understanding and validating MRI-derived markers such as MWF

Novel variant in glycophorin c gene protects against ribavirin-induced anemia during chronic hepatitis C treatment

Background: The current use of ribavirin in difficult-to-cure chronic hepatitis C patients (HCV) and patients with severe respiratory infections is constrained by the issue of ribavirin-induced hemolytic anemia that affects 30% of treated patients, requiring dosage modification or discontinuation. Though some genetic variants have been identified predicting this adverse effect, known clinical and genetic factors do not entirely explain the risk of ribavirin-induced anemia. Methods: We assessed the associations of previously identified variants in inosine triphosphatase (ITPA), solute carrier 28A2 (SLC28A2) and vitamin D receptor (VDR) genes with ribavirin-induced anemia defined as hemoglobin decline of ≥30 g/L on treatment, followed by a staged discovery (n = 114), replication (n = 74), and combined (n = 188) genome-wide association study to uncover potential new predictive variants. Results: We identified a novel association in the gene coding glycophorin C (rs6741425; OR:0.12, 95%CI:0.04–0.34, P = 2.94 × 10-6) that predicts protection against ribavirin-induced anemia. We also replicated the associations of ITPA and VDR genetic variants with the development of ribavirin-induced anemia (rs1127354; OR:0.13, 95%CI:0.04–0.41, P = 8.66 ×10-5; and rs1544410; OR:1.65, 95%CI:1.01–2.70, P = 0.0437). Conclusions: GYPC variation affecting erythrocyte membrane strength is important in predicting risk for developing ribavirin-induced anemia. ITPA and VDR genetic variants are also important predictors of this adverse reaction

Role of Cisplatin Dose Intensity and <i>TPMT </i>Variation in the Development of Hearing Loss in Children

Background:Cisplatin, widely used in the treatment of solid tumors, causes permanent hearing loss in more than 60% of treated children. Previous studies have implicated several clinical factors in the development of ototoxicity, including cumulative cisplatin dose. However, the role of cisplatin dose intensity in the development of hearing loss in children remains unclear. Pharmacogenetic studies have also identified genetic variants in TPMT that increase the risk of cisplatin-induced hearing loss. This study aims to determine whether cisplatin dose intensity contributes to the risk of hearing loss in children and whether genetic variations in TPMT further modifies the risk of cisplatin-induced hearing loss.Methods:The authors genotyped 371 cisplatin-treated children for the presence of any 3 TPMT-risk variants. Patients were categorized into high-, moderate-, and low-intensity cisplatin dosing groups according to the cisplatin dose administered per unit time. Kaplan-Meier curves were plotted to compare the cumulative incidence of hearing loss between the genotype and dose intensity groups.Results:Patients receiving cisplatin at high dose intensity experienced significantly higher incidences of ototoxicity than those receiving cisplatin at low dose intensity (P = 9 × 10-7). Further stratification by TPMT genotype revealed that carriers of ≥1 TPMT variants receiving high-intensity cisplatin developed ototoxicity sooner and more often than their wild-type counterparts (93.8% vs. 56.6% at 12 months; P = 5 × 10-5) and noncarriers receiving low-intensity cisplatin (21.2% at 12 months).Conclusions:Cisplatin dose intensity is strongly associated with ototoxicity development in children, and this risk is further increased by the presence of TPMT-risk alleles.</p

Role of Cisplatin Dose Intensity and TPMT Variation in the Development of Hearing Loss in Children

Background:Cisplatin, widely used in the treatment of solid tumors, causes permanent hearing loss in more than 60% of treated children. Previous studies have implicated several clinical factors in the development of ototoxicity, including cumulative cisplatin dose. However, the role of cisplatin dose intensity in the development of hearing loss in children remains unclear. Pharmacogenetic studies have also identified genetic variants in TPMT that increase the risk of cisplatin-induced hearing loss. This study aims to determine whether cisplatin dose intensity contributes to the risk of hearing loss in children and whether genetic variations in TPMT further modifies the risk of cisplatin-induced hearing loss.Methods:The authors genotyped 371 cisplatin-treated children for the presence of any 3 TPMT-risk variants. Patients were categorized into high-, moderate-, and low-intensity cisplatin dosing groups according to the cisplatin dose administered per unit time. Kaplan-Meier curves were plotted to compare the cumulative incidence of hearing loss between the genotype and dose intensity groups.Results:Patients receiving cisplatin at high dose intensity experienced significantly higher incidences of ototoxicity than those receiving cisplatin at low dose intensity (P = 9 × 10-7). Further stratification by TPMT genotype revealed that carriers of ≥1 TPMT variants receiving high-intensity cisplatin developed ototoxicity sooner and more often than their wild-type counterparts (93.8% vs. 56.6% at 12 months; P = 5 × 10-5) and noncarriers receiving low-intensity cisplatin (21.2% at 12 months).Conclusions:Cisplatin dose intensity is strongly associated with ototoxicity development in children, and this risk is further increased by the presence of TPMT-risk alleles