Recent advances in the molecular basis of Lafora’s progressive myoclonus epilepsy

Laforas disease (LD) is an autosomal recessive and fatal form of progressive myoclonus epilepsy with onset in late childhood or adolescence. LD is characterised by the presence of intracellular polyglucosan inclusions, called Lafora bodies, in tissues including the brain, liver and skin. Patients have progressive neurologic deterioration, leading to death within 10 years of onset. No preventive or curative treatment is available for LD. At least three genes underlie LD, of which two have been isolated and mutations characterised: EPM2A and NHLRC1. The EPM2A gene product laforin is a protein phosphatase while the NHLRC1 gene product malin is an E3 ubiquitin ligase that ubiquitinates and promotes the degradation of laforin. Analyses of the structure and function of these gene products suggest defects in post-translational modification of proteins as the common mechanism that leads to the formation of Lafora inclusion bodies, neurodegeneration and the epileptic phenotype of LD. In this review, we summarise the available information on the genetic basis of LD, and correlate these advances with the rapidly expanding information about the mechanisms of LD gained from studies on both cell biological and animal models. Finally, we also discuss a possible mechanism to explain the locus heterogeneity observed in LD.     

An SNP in protamine 1: a possible genetic cause of male infertility?

Gene targeting of the sperm nuclear proteins, the protamines, in mice leads to haploinsufficiency, abnormal chromatin compaction, sperm DNA damage, and male infertility. In order to investigate whether changes in amount or structure of the protamines could be a cause of human infertility, we sequenced the protamine genes of infertile men whose sperm appeared phenotypically similar to those of protamine deficient mice. We identified a heterozygous single nucleotide polymorphism (SNP) in the protamine (PRM1) gene in three infertile men (10% of the total infertile men analysed). This SNP disrupts one of the highly conserved arginine clusters needed for normal DNA binding. To rapidly screen for this SNP in infertile patients, we developed a simple PCR restriction fragment length polymorphism assay. This is the first report of a SNP in the PRM1 gene that appears associated with human male infertility.     

Accumulation of mitochondrial genome variations in Persian LQTS patients: a possible risk factor?

BackgroundLong QT syndrome (LQTS) is among arrhythmia disorders of the heart that causes sudden cardiac death in young individuals. As yet, most of investigations have focused on nuclear genome for finding genetic defects in this disorder, but some of the cases with LQTS cannot be explained by mutations of identified genes. On the other hand, it has been reported that the activity of ion channels in cardiomyocytes is sensitive to ATP level. It prompted us to focus on the mitochondrial DNA and monitor the point mutations of genome which are probably the cause of respiratory chain defects and reduced ATP generation.MethodsWe searched about 55% of the mitochondrial DNA (mtDNA) by temporal temperature gradient gel electrophoresis (TTGE), and DNA fragments showing abnormal banding patterns were sequenced for identification of exact mutations.ResultsIn 39 patients (33 familial and 6 sporadic cases), for the first time, we detected 35 mtDNA mutations in which 8 were novel (23%) and 27 (77%) have been reported in other mitochondrial diseases. Our results showed that these mutations in LQTS patients were higher than those in normal controls (P<.0001), and the number of mutations in LQTS patients with syncope is higher than in patients without syncope (P<.001).ConclusionsAs the mitochondrion's ATP synthesis is important in heart, it is possible that mutations and their accumulation in mtDNA could constitute a predisposing factor that in combination with environmental factors may trigger the syncope in patients with LQTS.     

Exome sequencing findings in 27 patients with myoclonic-atonic epilepsy: Is there a major genetic factor?

Myoclonic-atonic epilepsy (MAE) is thought to have a genetic etiology. Mutations in CHD2, SLC2A1 and SLC6A1 genes have been reported in few patients showing often intellectual disability prior to MAE onset. We aimed to explore putative causal genetic factors in MAE. We performed array-CGH and whole-exome sequencing in 27 patients. We considered non-synonymous variants, splice acceptor, donor site mutations, and coding insertions/deletions. A gene was causal when its mutations have been already linked to epilepsy or other brain diseases or when it has a putative function in neuronal excitability or brain development. We identified candidate disease-causing variants in 11 patients (41%). Single variants were found in some known epilepsy-associated genes (namely CHD2, KCNT1, KCNA2 and STXBP1) but not in others (SLC2A1 and SLC6A1). One new candidate gene SUN1 requires further validation. MAE shows underlying genetic heterogeneity with only few cases linked to mutations in genes reported in developmental and epileptic encephalopathies.     

Interictal spikes: Harbingers or causes of epilepsy?

Interictal spikes are brief paroxysmal electrographic discharges observed between spontaneous recurrent seizures in epileptic patients. The relationship between interictal spikes and the seizures that define acquired epilepsy has been debated for decades. Recent studies using long-term continuous electrographic recordings from the hippocampus and cortex in rats with kainate-induced epilepsy suggest that electrographic spikes, with waveforms similar to interictal spikes, precede the occurrence of the first spontaneous epileptic seizure. These data raise the possibility that spikes might serve as a surrogate marker of ongoing chronic epileptogenesis. Additionally, electrographic spikes might actually contribute to the development and maintenance of the epileptic state (i.e., the increased probability of spontaneous recurrent seizures). Correlational evidence for such a causal relationship has recently also been obtained in an in vitro model of epileptogenesis using organotypic hippocampal slices. Testing for a causal relationship will ultimately require selective anti-spike medications. Although no such agents currently exist, this new preparation is amenable to moderate-throughput screening, which should accelerate their discovery. Anti-spike agents may also be of benefit in ameliorating the cognitive dysfunctions associated with epilepsy, to which spike activity may contribute.     

Risk of genetic and epigenetic alteration in children conceived following ART: Is it time to return to nature whenever possible?

Assisted reproductive technology may influence epigenetic signature as the procedures coincide with the extensive epigenetic modification occurring from fertilization to embryo implantation. However, it is still unclear to what extent ART alters the embryo epigenome. In vivo fertilization occurs in the fallopian tube, where a specific and natural environment enables the embryo's healthy development. During this dynamic period, major waves of epigenetic reprogramming, crucial for the normal fate of the embryo, take place. Over the past decade, concerns relating to the raised incidence of epigenetic anomalies and imprinting following ART have been raised by several authors. Epigenetic reprogramming is particularly susceptible to environmental conditions during the periconceptional period; therefore, unphysiological conditions, including ovarian stimulation, in vitro fertilization, embryo culture, cryopreservation of gametes and embryos, parental lifestyle, and underlying infertility, have the potential to contribute to epigenetic dysregulation independently or collectively. This review critically appraises the evidence relating to the association between ART and genetic and epigenetic modifications that may be transmitted to the offspring.     

T-tubule formation in cardiacmyocytes: two possible mechanisms?

We have followed the differentiation of transverse (T) tubules and of the associations between sarcoplasmic reticulum (SR) and either the plasmalemma (peripheral couplings) or the T tubules (dyads) in postnatal rat ventricular myocytes using electron microscopy. Dyads and peripheral couplings are collectively called Ca²⁺ Release Units (CRUs) because they are the sites at which Ca²⁺ is released from the SR. Profiles of T tubules, caveolae and dyads are mostly at the cell edge in early postnatal days and are found with increased frequency in the cell interior during the first two postnatal weeks. Using ferritin to trace continuity of T tubules lumen with the extracellular space, we find that some of T tubules (between ∼6 and 25%), either singly or within dyads, lack ferritin in their lumen. The percentage of tubules that do not contain ferritin decreases slightly during postnatal differentiation and is not very different at the cells’ edges and interior. We propose that T tubules form as invaginations of the plasmalemma that penetrate inward driven by accrual of membrane lipids and specific proteins. This occurs by a dual mechanism: either by the independent flow of SR and T tubule proteins into the two separate membranes or by the fusion of preformed vesicle tandems into the dyads. Most of the CRUs (∼86%) are constituted by peripheral couplings and ferritin containing dyads, thus constituting CRUs in which Ca²⁺ release from the SR is initiated by a membrane depolarization. In the remaining CRUs, activation of Ca²⁺ release must be dependent on some other mechanisms.     

Anti-astrocyte autoantibodies in Guillain-Barre Syndrome--possible involvement in the pathophysiology of a psychosyndrome?

Guillain-Barre syndrome (GBS) is an autoimmune disorder of the peripheral nervous system. However, GBS patients frequently display a psychosyndrome, indicating an accompanying involvement of the central nervous system (CNS), although the cause is not understood. Hepatic encephalopathy is possibly the best characterized example of a psychosyndrome, and astrocyte dysfunction appears to play a major role. We hypothesized that if compromised astrocyte function is of general importance in the pathomechanism of a psychosyndrome, then astrocytes should be involved in the CNS dysfunctions of GBS patients as well. Using immunocytochemistry, we found anti-astrocyte autoantibodies in about 60% of GBS patients and few or none in control groups. This finding was confirmed by Western blots. Our data are consistent with the suspected importance of an impaired astrocyte function in the pathomechanism of a psychosyndrome.     

Diagnosis of progressive supranuclear palsy: can measurement of tau forms help?

Recently, a new assay for the differential diagnosis of progressive supranuclear palsy (PSP) was proposed. It was shown that the ratio of 33/55 kDa tau forms in cerebrospinal fluid (CSF) was specifically reduced in PSP CSF. We aimed to reproduce these results, but were not able to detect the tau forms in CSF. We demonstrate that i) CSF total tau levels are too low to be detected by the published protocol, and ii) the described 33 and 55 kDa bands are likely the heavy and light chains of IgG used in the assay. We conclude that more sensitive techniques are needed to measure tau forms in CSF.     

Intranasal anticonvulsive treatment: A prospective management of intractable epilepsy?

As a common human disorder, epilepsy affects about 0.5% of the population. In many patients with epilepsy, seizures are well-controlled with currently available anti-epileptic drugs, but around 35% of patients with epilepsy continue to have seizures despite carefully optimized drug treatment. Recently, intrinsic or acquired overexpression of multidrug transporters in the blood-brain barrier has been suggested to result in producing pharmacoresistance in epilepsy, for anti-epileptic drugs concentrations would be reduced to the level that is insufficient to cause anti-epileptic activity. Intranasal administration provides a direct transport pathway to brain tissue that circumvents the blood-brain barrier for many drugs and neuropeptides. These significant conditions support the hypothesis that intranasal anticonvulsive treatment may be a prospective management of intractable epilepsy. Unfortunately, there are few studies on intranasal anticonvulsive treatment conducted in the field of intractable epilepsy. Our hypothesis provides not only a new alternative treatment for intractable epilepsy but also has potential for investigating the mechanisms underlying the development of pharmacoresistance in epilepsy.     

Mirroring and mu rhythm involvement in social cognition: Are there dissociable subcomponents of theory of mind?

Tager-Flusberg and Sullivan [Tager-Flusberg, H., Sullivan, K., 2000. A componential view of theory of mind: evidence from Williams syndrome. Cognition 76, 59–90] have argued for a distinction between the social-perceptive component of theory of mind (ToM), involving judgment of mental state from facial and body expressions, and the social-cognitive component, which is representation-based and linked to language and theory-building. This is analogous to the distinction made by others [Gallese, V., Keysers, C., Rizzolatti, G., 2004. A unifying view of the basis of social cognition. Trends in Cognitive Science 8, 396–403] between representing the mental state of another as if it was one's own (simulation theory), which requires involvement of the mirror neuron system, and explicit or declarative reasoning about mental states (theory theory), which does not. This componential view of ToM was tested by examining mirroring, as indexed by EEG mu rhythm suppression, in subjects performing tasks assumed to tap both dimensions. Mu suppression was positively correlated with accuracy on the social-perceptual task but not in the social-cognitive task. In a ToM control task requiring judgments about person–object interactions accuracy was correlated with mu suppression. This implies that mirroring is involved in making judgments about emotions and person–object interactions. However, mirroring is insensitive to the distinction between correct and incorrect inferences in the social-cognitive task suggesting that additional mechanisms are needed to make mental attributions of beliefs and intentions. These results are consistent with a refined componential view of ToM.     

Implications of structural variations in the human sacrum: why is an anatomical classification crucial?

Purpose

An array of diversity in sacral anatomy including lumbosacral transitional variations is commonly found in the general population. These anatomical variations involve alterations in number of sacral segments, auricular surface area, and neural arch dimensions and are associated with biomechanical, surgical and obstetric implications.

Methods

The present study reports screening >300 dried human sacral specimens and grouping them based on the common variations observed specifically in context of the number of sacral segments, position of the auricular surfaces, and type of the neural arch components.

Results

Screening and grouping of the samples presented a five-group classification and coding system that incorporates specific structural characteristic in a sacrum.

Conclusion

The grouping and coding system developed in this study classifies variabilities associated with sacral anatomy along a common-to-rare anatomical spectrum that may provide handy information needed in a clinical, biomechanical, obstetric or medico-legal context.

     

Interleukin-1β stimulates the secretion of thymic stromal lymphopoietin (TSLP) from endometrioma stromal cells: possible involvement of TSLP in endometriosis

STUDY QUESTION: Is thymic stromal lymphopoietin (TSLP) involved in the pathophysiology of endometriosis? SUMMARY ANSWER: TSLP is up-regulated by interleukin (IL)-1β and may be involved in the development of endometriosis. WHAT IS KNOWN ALREADY: Endometriosis is a chronic inflammatory disease in which the Th2 immune response is activated and has been suggested to promote the disease. TSLP is a master cytokine that drive Th2 immune response. STUDY DESIGN, SIZE, DURATION: A laboratory study. PARTICIPANTS/MATERIALS, SETTING, METHODS: Primary cultures of endometrioma stromal cells (ESCs) were treated with IL-1β, a typical inflammatory cytokine associated with endometriosis. Gene expression of TSLP in ESCs and secretion of TSLP protein from ESCs were studied using quantitative PCR and a specific ELISA. Interferon γ (IFNγ), a typical Th1 cytokine, and IL-4, a typical Th2 cytokine, were added to the culture to evaluate their effect on the IL-1β-induced secretion of TSLP. Inhibitors of p38 mitogen-activated protein kinase (MAPK), p42/44 MAPK and stress-activated protein kinase/Jun amino-terminal kinase (SAPK/JNK) were added to the culture to examine intracellular signals involved in IL-1β-induced TSLP secretion. The expression of TSLP in endometrioma tissue was examined by immunohistochemistry. The concentration of TSLP in the serum and peritoneal fluid (PF) of women with or without endometriosis was measured with a specific ELISA. MAIN RESULTS AND THE ROLE OF CHANCE: IL-1β stimulated the expression of TSLP mRNA and secretion of TSLP protein from ESCs. IL-4 enhanced the IL-1β-induced TSLP secretion from ESCs, while IFNγ reduced it. Inhibitors of p42/44 MAPK, p38 MAPK and SAPK/JNK suppressed the IL-1β-induced secretion of TSLP from ESCs. Positive immunostaining of TSLP was observed in the stroma of endometrioma tissue. TSLP concentrations in the serum and PF were both higher in women with endometriosis compared with those without endometriosis. LIMITATIONS, REASONS FOR CAUTION: The present study was only in vitro. The samples used for culture were endometrioma tissues, not including other types of endometriosis. Therefore, the present findings should be interpreted with caution. WIDER IMPLICATIONS OF THE FINDINGS: This study provided new insights in the Th2 immune response-related mechanism in endometriosis. STUDY FUNDING: This study is partly supported by grants from the Ministry of Health, Labour and Welfare, and the Ministry of Education, Culture, Sports, Science and Technology. The authors have no conflicts of interest to declare.