Sequential expression of Efhc1/myoclonin1 in choroid plexus and ependymal cell cilia

EFHC1 gene mutation profile of Turkish JME patients and its association with disease risk

OBJECTIVES

Juvenile myoclonic epilepsy (JME) is a common form of generalized epilepsy with an important genetic component. This cohort study aimed to examine the frequency of EFHC1 gene variants in Turkish JME patients and a healthy control group and evaluate the association between these mutations and disease risk.

METHODS

We screened 72 JME patients with a mean age of 31.8 ± 9.9 (20-65) years and 35 controls with a mean age of 29.1 ± 7.6 (17-50) years from southern Turkey using direct sequencing analyses.

RESULTS

EFCH1 single nucleotide variants were detected in 24 of 72 JME patients and 3 of 35 controls. The most common mutations were R182H in JME patients (p = 0.010) and 3'UTR in the control group (p < 0.001). The R182H mutation is a common variant in JME (95 % CI: 1.232-76.580, p = 0.031) and the 3'UTR mutation may be associated with lower risk of JME in the Turkish population (95 % CI: 13.89-166.67, p < 0.001).

SIGNIFICANCE

Our results indicate that EFHC1 gene variants carry a risk for JME and the 3'UTR variant may have a protective role against JME in the Turkish population. Screening for other genes is needed to further clarify the genetic inheritance of JME in Turkish patients.

DNAH14 variants are associated with neurodevelopmental disorders

Neurodevelopmental disorders (NDD) are complex and multifaceted diseases involving genetic and environmental science. The rapid development of sequencing techniques makes it possible to dig new disease-causing genes. Our study was aimed to discover novel genes linked to NDD. Trio whole-exome sequencing was performed to evaluate potential variants of NDD, identifying three unrelated patients with compound heterozygous variants in DNAH14. The detailed clinical information and genetic results of the recruited patients were obtained and systematically reviewed. Three compound heterozygous DNAH14 variants were identified (c.6100C>T(p.Arg2034Ter) and (c.5167A>G(p.Arg1723Gly), c.12640_12641delAA (p.Lys4214Valfs*7) and (c.4811T>A(p.Leu1604Gln), c.7615C>A(p.Pro2539Thr) and c.11578G>A (p.Gly3860Ser)), including one nonsense variant, one frameshift variant and four missense variants, which were all not exist or with low minor allele frequency based on the gnomAD database. The missense variants were all assumed to be damaging or probably damaging by multiple bioinformatics tools. Four of these variants were located in the AAA+ ATPase domain and two were located in the C-terminal domain. Most affected amino acids were highly conserved in various species. A spectrum of neurological and developmental phenotypes was observed including seizure, global developmental delay, microcephaly and hypotonia. Our findings indicate that variants in DNAH14 could lead to previously unrecognized neurodevelopmental disorders. This article is protected by copyright. All rights reserved.

Epilepsy protein Efhc1/myoclonin1 is expressed in cells with motile cilia but not in neurons or mitotic apparatuses in brain

EFHC1 gene encodes the myoclonin1 protein, also known as Rib72-1. Pathogenic variants in EFHC1 have been reported in patients with juvenile myoclonic epilepsy (JME). Although several studies of immunohistological investigations reproducibly showed that the myoclonin1 is expressed in cells with flagella and motile cilia such as sperm, trachea and ependymal cells lining the brain ventricles, whether myoclonin1 is also expressed in neurons still remains controversial. Here we investigated myoclonin1 expression using widely-used polyclonal (mRib72-pAb) and self-made monoclonal (6A3-mAb) anti-myoclonin1 antibodies together with Efhc1 homozygous knock-out (Efhc1^-/-) mice. All of the western blot, immunocytochemical, and immunohistochemical analyses showed that mRib72-pAb crossreacts with several mouse proteins besides myoclonin1, while 6A3-mAb specifically recognized myoclonin1 and detected it only in cells with motile cilia but not in neurons. In dividing cells, mRib72-pAb signals were observed at the midbody (intercellular bridge) and mitotic spindle, but 6A3-mAb did not show any signals at these apparatuses. We further found that the complete elimination of myoclonin1 in Efhc1^-/- mouse did not critically affect cell division and migration of neurons in cerebral cortex. These results indicate that myoclonin1 is not expressed in neurons, not a regulator of cell division or neuronal migration during cortical development, but expressed in choroid plexus and ependymal cells and suggest that EFHC1 mutation-dependent JME is a motile ciliopathy.

A systems biology framework integrating GWAS and RNA-seq to shed light on the molecular basis of sperm quality in swine

BACKGROUND

Genetic pressure in animal breeding is sparking the interest of breeders for selecting elite boars with higher sperm quality to optimize ejaculate doses and fertility rates. However, the molecular basis of sperm quality is not yet fully understood. Our aim was to identify candidate genes, pathways and DNA variants associated to sperm quality in swine by analysing 25 sperm-related phenotypes and integrating genome-wide association studies (GWAS) and RNA-seq under a systems biology framework.

RESULTS

By GWAS, we identified 12 quantitative trait loci (QTL) associated to the percentage of head and neck abnormalities, abnormal acrosomes and motile spermatozoa. Candidate genes included CHD2, KATNAL2, SLC14A2 and ABCA1. By RNA-seq, we identified a wide repertoire of mRNAs (e.g. PRM1, OAZ3, DNAJB8, TPPP2 and TNP1) and miRNAs (e.g. ssc-miR-30d, ssc-miR-34c, ssc-miR-30c-5p, ssc-miR-191, members of the let-7 family and ssc-miR-425-5p) with functions related to sperm biology. We detected 6128 significant correlations (P-value ≤ 0.05) between sperm traits and mRNA abundances. By expression (e)GWAS, we identified three trans-expression QTL involving the genes IQCJ, ACTR2 and HARS. Using the GWAS and RNA-seq data, we built a gene interaction network. We considered that the genes and interactions that were present in both the GWAS and RNA-seq networks had a higher probability of being actually involved in sperm quality and used them to build a robust gene interaction network. In addition, in the final network we included genes with RNA abundances correlated with more than four semen traits and miRNAs interacting with the genes on the network. The final network was enriched for genes involved in gamete generation and development, meiotic cell cycle, DNA repair or embryo implantation. Finally, we designed a panel of 73 SNPs based on the GWAS, eGWAS and final network data, that explains between 5% (for sperm cell concentration) and 36% (for percentage of neck abnormalities) of the phenotypic variance of the sperm traits.

CONCLUSIONS

By applying a systems biology approach, we identified genes that potentially affect sperm quality and constructed a SNP panel that explains a substantial part of the phenotypic variance for semen quality in our study and that should be tested in other swine populations to evaluate its relevance for the pig breeding sector.

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.

PACRG, a protein linked to ciliary motility, mediates cellular signaling

Cilia are cellular projections that can be motile to generate fluid flow or nonmotile to enable signaling. Both forms are based on shared components, and proteins involved in ciliary motility, like PACRG, may also function in ciliary signaling. Caenorhabditis elegans PACRG acts in a subset of nonmotile cilia to influence a learning behavior and promote longevity.

Cilia are microtubule-based organelles that project from nearly all mammalian cell types. Motile cilia generate fluid flow, whereas nonmotile (primary) cilia are required for sensory physiology and modulate various signal transduction pathways. Here we investigate the nonmotile ciliary signaling roles of parkin coregulated gene (PACRG), a protein linked to ciliary motility. PACRG is associated with the protofilament ribbon, a structure believed to dictate the regular arrangement of motility-associated ciliary components. Roles for protofilament ribbon–associated proteins in nonmotile cilia and cellular signaling have not been investigated. We show that PACRG localizes to a small subset of nonmotile cilia in Caenorhabditis elegans, suggesting an evolutionary adaptation for mediating specific sensory/signaling functions. We find that it influences a learning behavior known as gustatory plasticity, in which it is functionally coupled to heterotrimeric G-protein signaling. We also demonstrate that PACRG promotes longevity in C. elegans by acting upstream of the lifespan-promoting FOXO transcription factor DAF-16 and likely upstream of insulin/IGF signaling. Our findings establish previously unrecognized sensory/signaling functions for PACRG and point to a role for this protein in promoting longevity. Furthermore, our work suggests additional ciliary motility-signaling connections, since EFHC1 (EF-hand containing 1), a potential PACRG interaction partner similarly associated with the protofilament ribbon and ciliary motility, also positively regulates lifespan.

Identifying domains of EFHC1 involved in ciliary localization, ciliogenesis, and the regulation of Wnt signaling

EFHC1 encodes a ciliary protein that has been linked to Juvenile Myoclonic Epilepsy. In ectodermal explants, derived from Xenopus laevis embryos, the morpholino-mediated down-regulation of EFHC1b inhibited multiciliated cell formation. In those ciliated cells that did form, axoneme but not basal body formation was inhibited. EFHC1b morphant embryos displayed defects in central nervous system (CNS) and neural crest patterning that were rescued by a EFHC1b-GFP chimera. EFHC1b-GFP localized to ciliary axonemes in epidermal, gastrocoele roof plate, and neural tube cells. In X. laevis there is a link between Wnt signaling and multiciliated cell formation. While down-regulation of EFHC1b led to a ~2-fold increase in the activity of the β-catenin/Wnt-responsive TOPFLASH reporter, EFHC1b-GFP did not inhibit β-catenin activation of TOPFLASH. Wnt8a RNA levels were increased in EFHC1b morphant ectodermal explants and intact embryos, analyzed prior to the on-set of ciliogenesis. Rescue of the EFHC1b MO's ciliary axonemal phenotypes required the entire protein; in contrast, the EFHC1b morpholino's Wnt8a, CNS, and neural crest phenotypes were rescued by a truncated form of EFHC1b. The EFHC1b morpholino's Wnt8a phenotype was also rescued by the injection of RNAs encoding secreted Wnt inhibitors, suggesting that these phenotypes are due to effects on Wnt signaling, rather than the loss of cilia, an observation of potential relevance to understanding EFHC1's role in human neural development.

Juvenile myoclonic epilepsy as a possible neurodevelopmental disease: role of EFHC1 or Myoclonin1

Juvenile Myoclonic Epilepsy (JME) accounts for almost 12% of all epilepsies and is one of the most frequent forms of genetic generalized epilepsies. Genetic studies have revealed that mutations in EFHC1 (EF-hand containing one) account for 3 to 9% of all cases around the world. This gene encodes a protein that is not an ion channel, and several studies have tried to find its cellular role. In this article, we review the various functions that have been proposed for this protein. Interestingly, all of them could affect brain development at different steps, suggesting that the developmental assembly of neural circuits may play a prominent role in JME.

Re-evaluation of myoclonin1 immunosignals in neuron, mitotic spindle, and midbody--nonspecific?

Mutations in EFHC1 gene cause juvenile myoclonic epilepsy (JME). We previously showed that myoclonin1 protein encoded by EFHC1 is expressed in prenatal choroid plexus and postnatal ependymal cell cilia but may not be in neurons. However, another group reported that myoclonin1 is expressed in neurons and at mitotic spindle, and that the suppression of EFHC1 by RNAi caused disruption of mitotic spindle structure, impaired M-phase progression, and an increase of apoptosis. We re-investigated their results by using the same polyclonal antibody that they used, and found that the signals in neurons remained in Efhc1-deficient mouse, suggesting that the signals in neurons were nonspecific. Furthermore, Efhc1 (-/-) mouse did not show any abnormalities such as disruption of mitotic spindle structure, impaired M-phase progression, and an increase of apoptosis. Further investigations are required to clarify these discrepancies.

A common susceptibility factor of both autism and epilepsy: functional deficiency of GABA A receptors

Autism and epilepsy are common childhood neurological disorders with a great heterogeneity of clinical phenotypes as well as risk factors. There is a high co-morbidity of autism and epilepsy. The neuropathology of autism and epilepsy has similar histology implicating the processes of neurogenesis, neural migration, programmed cell death, and neurite outgrowth. Genetic advances have identified multiple molecules that participate in neural development, brain network connectivity, and synaptic function which are involved in the pathogenesis of autism and epilepsy. Mutations in GABA(A) receptor subunit have been frequently associated with epilepsy, autism, and other neuropsychiatric disorders. In this paper, we address the hypothesis that functional deficiency of GABAergic signaling is a potential common molecular mechanism underpinning the co-morbidity of autism and epilepsy.

Mutations of EFHC1, linked to juvenile myoclonic epilepsy, disrupt radial and tangential migrations during brain development

Heterozygous mutations in Myoclonin1/EFHC1 cause juvenile myoclonic epilepsy (JME), the most common form of genetic generalized epilepsies, while homozygous F229L mutation is associated with primary intractable epilepsy in infancy. Heterozygous mutations in adolescent JME patients produce subtle malformations of cortical and subcortical architecture, whereas homozygous F229L mutation in infancy induces severe brain pathology and death. However, the underlying pathological mechanisms for these observations remain unknown. We had previously demonstrated that EFHC1 is a microtubule-associated protein (MAP) involved in cell division and radial migration during cerebral corticogenesis. Here, we show that JME mutations, including F229L, do not alter the ability of EFHC1 to colocalize with the centrosome and the mitotic spindle, but act in a dominant-negative manner to impair mitotic spindle organization. We also found that mutants EFHC1 expression disrupted radial and tangential migration by affecting the morphology of radial glia and migrating neurons. These results show how Myoclonin1/EFHC1 mutations disrupt brain development and potentially produce structural brain abnormalities on which epileptogenesis is established.

Proteomic analysis of multiple primary cilia reveals a novel mode of ciliary development in mammals

Cilia are structurally and functionally diverse organelles, whose malfunction leads to ciliopathies. While recent studies have uncovered common ciliary transport mechanisms, limited information is available on the proteome of cilia, particularly that of sensory subtypes, which could provide insight into their functional and developmental diversities. In the present study, we performed proteomic analysis of unique, multiple 9+0 cilia in choroid plexus epithelial cells (CPECs). The analysis of juvenile swine CPEC cilia identified 868 proteins. Among them, 396 were shared with the proteome of 9+0 photoreceptor cilia (outer segment), whereas only 152 were shared with the proteome of 9+2 cilia and flagella. Various signaling molecules were enriched in a CPEC-specific ciliome subset, implicating multiplicity of sensory functions. The ciliome also included molecules for ciliary motility such as Rsph9. In CPECs from juvenile swine or adult mouse, Rsph9 was localized to a subpopulation of cilia, whereas they were non-motile. Live imaging of mouse choroid plexus revealed that neonatal CPEC cilia could beat vigorously, and the motility waned and was lost within 1–2 weeks. The beating characteristics of neonatal CPEC cilia were variable and different from those of typical 9+2 cilia of ependyma, yet an Efhc1-mediated mechanism to regulate the beating frequency was shared in both types of cilia. Notably, ultrastructural analysis revealed the presence of not only 9+0 but also 9+2 and atypical ciliary subtypes in neonatal CPEC. Overall, these results identified both conserved and variable components of sensory cilia, and demonstrated a novel mode of ciliary development in mammals.

The juvenile myoclonic epilepsy-related protein EFHC1 interacts with the redox-sensitive TRPM2 channel linked to cell death

The transient receptor potential M2 channel (TRPM2) is the Ca(2+)-permeable cation channel controlled by cellular redox status via β-NAD(+) and ADP-ribose (ADPR). TRPM2 activity has been reported to underlie susceptibility to cell death and biological processes such as inflammatory cell migration and insulin secretion. However, little is known about the intracellular mechanisms that regulate oxidative stress-induced cell death via TRPM2. We report here a molecular and functional interaction between the TRPM2 channel and EF-hand motif-containing protein EFHC1, whose mutation causes juvenile myoclonic epilepsy (JME) via mechanisms including neuronal apoptosis. In situ hybridization analysis demonstrates TRPM2 and EFHC1 are coexpressed in hippocampal neurons and ventricle cells, while immunoprecipitation analysis demonstrates physical interaction of the N- and C-terminal cytoplasmic regions of TRPM2 with the EFHC1 protein. Coexpression of EFHC1 significantly potentiates hydrogen peroxide (H(2)O(2))- and ADPR-induced Ca(2+) responses and cationic currents via recombinant TRPM2 in HEK293 cells. Furthermore, EFHC1 enhances TRPM2-conferred susceptibility of HEK293 cells to H(2)O(2)-induced cell death, which is reversed by JME mutations. These results reveal a positive regulatory action of EFHC1 on TRPM2 activity, suggesting that TRPM2 contributes to the expression of JME phenotypes by mediating disruptive effects of JME mutations of EFHC1 on biological processes including cell death.

NDP kinase 7 is a conserved microtubule-binding protein preferentially expressed in ciliated cells

Nucleoside diphosphate (NDP) kinase is an enzyme that synthesizes the nucleoside triphosphates. In mammals, nine sequences (NDK1-NDK9) have been found with domain(s) homologous to the catalytic domain of NDP kinase, and some of them have been shown to associate with sperm flagella. The present study examines the localization of NDK7, for which little information has been available. Database analysis showed that the NDK7 gene is present in organisms with cilia and flagella. Western blotting analyses of various mouse tissues consistently indicated that NDK7 is preferentially expressed in tissues with motile cilia as well as in sperm. Immunofluorescence microscopy revealed that this protein is localized along the entire length of the TritonX-100-insoluble fraction of sperm flagella, possibly in the axonemes. Unexpectedly, however, NDK7 in tracheal epithelia was found in the cell body but not in cilia. Finally, in vitro co-sedimentation assays using recombinant proteins showed that both mouse and Chlamydomonas NDK7 directly bind to microtubules.

Distribution of EFHC1 or Myoclonin 1 in mouse neural structures

EFHC1, a gene mutated in juvenile myoclonic epilepsy, encodes EFHC1, a protein with three DM10 domains and one EF-hand motif. We recently demonstrated that this molecule is a microtubule-associated protein (MAP) implicated in neuronal migration. Because some controversies persist about the precise localization in the CNS, we studied the neuroanatomical distribution of EFHC1 in mature and developing mouse brain. In the adult, low mRNA expression was detected in several brain structures such as cortex, striatum, hippocampus and cerebellum. At E16, EFHC1 mRNA was shown to be expressed in cortex and not only in cells lining ventricles. Using a purified polyclonal antibody, EFHC1 staining was observed in all cortical layers, in piriform cortex, in hippocampus and in Purkinje cells of cerebellum. In the cortex, the majority of EFHC1 positive cells correspond to neurons, however some glial cells were also stained. In agreement with a previous study, we demonstrated strong EFHC1 expression in cilia of ependymal cells lining cerebral ventricles. Moreover, at E16, the protein was observed at the borders of brain ventricles, in choroid plexus, but also, although to a lesser extent, in piriform and neocortex. In these latter structures, the pattern of expression seems to correspond to the extensions of the radial glia fibers as demonstrated by BLBP immunostaining. Finally, we confirmed that EFHC1 was also expressed and co-localized with the mitotic spindle of neural stem cells. These results confirm that EFHC1 is a protein with a likely low expression level in mouse brain but detectable both in adult and embryonic brain supporting our previous data and hypothesis that EFHC1 could play an important role during brain development. As discussed, this opens the door to a new conceptual approach viewing some idiopathic generalized epilepsies as developmental diseases instead of classical channelopathies.

EFHC1 interacts with microtubules to regulate cell division and cortical development

Mutations in the EFHC1 gene are linked to juvenile myoclonic epilepsy (JME), one of the most frequent forms of idiopathic generalized epilepsies. JME is associated with subtle alterations of cortical and subcortical architecture, but the underlying pathological mechanism remains unknown. We found that EFHC1 is a microtubule-associated protein involved in the regulation of cell division. In vitro, EFHC1 loss of function disrupted mitotic spindle organization, impaired M phase progression, induced microtubule bundling and increased apoptosis. EFHC1 impairment in the rat developing neocortex by ex vivo and in utero electroporation caused a marked disruption of radial migration. We found that this effect was a result of cortical progenitors failing to exit the cell cycle and defects in the radial glia scaffold organization and in the locomotion of postmitotic neurons. Therefore, we propose that EFHC1 is a regulator of cell division and neuronal migration during cortical development and that disruption of its functions leads to JME.

Neurons that fire together also conspire together: is normal sleep circuitry hijacked to generate epilepsy?

Brain circuits oscillate during sleep. The same circuits appear to generate pathological oscillations. In this review, we discuss recent advances in our understanding of how epilepsy co-opts normal, sleep-related circuits to generate seizures.

Efhc1 deficiency causes spontaneous myoclonus and increased seizure susceptibility

Mutations in EFHC1 gene have been previously reported in patients with epilepsies, including those with juvenile myoclonic epilepsy. Myoclonin1, also known as mRib72-1, is encoded by the mouse Efhc1 gene. Myoclonin1 is dominantly expressed in embryonic choroid plexus, post-natal ependymal cilia, tracheal cilia and sperm flagella. In this study, we generated viable Efhc1-deficient mice. Most of the mice were normal in outward appearance, and both sexes were found to be fertile. However, the ventricles of the brains were significantly enlarged in the null mutants, but not in the heterozygotes. Although the ciliary structure was found intact, the ciliary beating frequency was significantly reduced in null mutants. In adult stages, both the heterozygous and null mutants developed frequent spontaneous myoclonus. Furthermore, the threshold of seizures induced by pentylenetetrazol was significantly reduced in both heterozygous and null mutants. These observations seem to further suggest that decrease or loss of function of myoclonin1 may be the molecular basis for epilepsies caused by EFHC1 mutations.