Brainwaves beyond diagnosis: Wider applications of electroencephalography in idiopathic generalized epilepsy

Electroencephalography (EEG) has long been used as a versatile and noninvasive diagnostic tool in epilepsy. With the advent of digital EEG, more advanced applications of EEG have emerged. Compared with technologically advanced practice in focal epilepsies, the utilization of EEG in idiopathic generalized epilepsy (IGE) has been lagging, often restricted to a simple diagnostic tool. In this narrative review, we provide an overview of broader applications of EEG beyond this narrow scope, discussing how the current clinical and research applications of EEG may potentially be extended to IGE. The current literature, although limited, suggests that EEG can be used in syndromic classification, guiding antiseizure medication therapy, predicting prognosis, unraveling biorhythms, and investigating functional brain connectivity of IGE. We emphasize the need for longer recordings, particularly 24-h ambulatory EEG, to capture discharges reflecting circadian and sleep-wake cycle-associated variations for wider EEG applications in IGE. Finally, we highlight the challenges and limitations of the current body of literature and suggest future directions to encourage and enhance more extensive applications of this potent tool.

IDH1 gene mutation activates Smad signaling molecules to regulate the expression levels of cell cycle and biological rhythm genes in human glioma U87‑MG cells

Isocitrate dehydrogenase1 (IDH1) mutation is the most important genetic change in glioma. The most common IDH1 mutation results in the amino acid substitution of arginine 132 (Arg/R132), which is located at the active site of the enzyme. IDH1 Arg132His (R132H) mutation can reduce the proliferative rate of glioma cells. Numerous diseases follow circadian rhythms, and there is growing evidence that circadian disruption may be a risk factor for cancer in humans. Dysregulation of the circadian clock serves an important role in the development of malignant tumors, including glioma. Brain-Muscle Arnt-Like protein 1 (BMAL1) and Circadian Locomotor Output Cycles Kaput (CLOCK) are the main biological rhythm genes. The present study aimed to further study whether there is an association between IDH1 R132H mutation and biological rhythm in glioma, and whether this affects the occurrence of glioma. The Cancer Genome Atlas (TCGA) database was used to detect the expression levels of the biological rhythm genes BMAL1 and CLOCK in various types of tumor. Additionally, U87-MG cells were infected with wild-type and mutant IDH1 lentiviruses. Colony formation experiments were used to detect cell proliferation in each group, cell cycle distribution was detected by flow cytometry and western blotting was used to detect the expression levels of wild-type and mutant IDH1, cyclins, biological rhythm genes and Smad signaling pathway-associated genes in U87-MG cells. TCGA database results suggested that BMAL1 and CLOCK were abnormally expressed in glioma. Cells were successfully infected with wild-type and mutant IDH1 lentiviruses. Colony formation assay revealed decreased cell proliferation in the IDH1 R132H mutant group. The cell cycle distribution detected by flow cytometry indicated that IDH1 gene mutation increased the G₁ phase ratio and decreased the S phase ratio in U87-MG cells. The western blotting results demonstrated that IDH1 R132H mutation decreased the expression levels of the S phase-associated proteins Cyclin A and CDK2, and increased the expression levels of the G₁ phase-associated proteins Cyclin D3 and CDK4, but did not significantly change the expression levels of the G₂/M phase-associated protein Cyclin B1. The expression levels of the positive and negative rhythm regulation genes BMAL1, CLOCK, period (PER s (PER1, 2 and 3) and cryptochrom (CRY)s (CRY1 and 2) were significantly decreased, those of the Smad signaling pathway-associated genes Smad2, Smad3 and Smad2-3 were decreased, and those of phosphorylated (p)-Smad2, p-Smad3 and Smad4 were increased. Therefore, the present results suggested that the IDH1 R132H mutation may alter the cell cycle and biological rhythm genes in U87-MG cells through the TGF-β/Smad signaling pathway.

Variability in the Drug Response of M4 Muscarinic Receptor Knockout Mice During Day and Night Time

Mice are nocturnal animals. Surprisingly, the majority of physiological/pharmacological studies are performed in the morning, i.e., in the non-active phase of their diurnal cycle. We have shown recently that female (not male) mice lacking the M₄ muscarinic receptors (MR, M₄KO) did not differ substantially in locomotor activity from their wild-type counterparts (C57Bl/6Tac) during the inactive period. Increased locomotion has been shown in the active phase of their diurnal cycle. We compared the effects of scopolamine, oxotremorine, and cocaine on locomotor response, hypothermia and spontaneous behavior in the open field arena in the morning (9:00 AM) and in the evening (9:00 PM) in WT and in C57Bl/6NTac mice lacking the M₄ MR. Furthermore, we also studied morning vs. evening densities of muscarinic, GABA_A, D₁-like, D₂-like, NMDA and kainate receptors using autoradiography in the motor, somatosensory and visual cortex and in the striatum, thalamus, hippocampus, pons, and medulla oblongata. At 9:00 AM, scopolamine induced an increase in motor activity in WT and in M₄KO, yet no significant increase was observed at 9:00 PM. Oxotremorine induced hypothermic effects in both WT and M₄KO. Hypothermic effects were more evident in WT than in M₄KO. Hypothermia in both cases was more pronounced at 9:00 AM than at 9:00 PM. Cocaine increased motor activity when compared to saline. There was no difference in behavior in the open field between WT and M₄KO when tested at 9:00 AM; however, at 9:00 PM, activity of M₄KO was doubled in comparison to that of WT. Both WT and KO animals spent less time climbing in their active phase. Autoradiography revealed no significant morning vs. evening difference. Altogether, our results indicate the necessity of comparing morning vs. evening drug effects

The deletion of M4 muscarinic receptors increases motor activity in females in the dark phase

OBJECTIVES

M4 muscarinic receptors (MR) presumably play a role in motor coordination. Previous studies have shown different results depending on genetic background and number of backcrosses. However, no attention has been given to biorhythms.

MATERIAL AND METHODS

We therefore analyzed biorhythms under a light/dark cycle obtained telemetrically in intact animals (activity, body temperature) in M4 KO mice growth on the C57Bl6 background using ChronosFit software. Studying pure effects of gene knockout in daily rhythms is especially important knowledge for pharmacological/behavioral studies in which drugs are usually tested in the morning.

RESULTS

We show that M4 KO mice motor activity does not differ substantially from wild-type mice during light period while in the dark phase (mice active part of the day), the M4 KO mice reveal biorhythm changes in many parameters. Moreover, these differences are sex-dependent and are evident in females only. Mesor, night-day difference, and night value were doubled or tripled when comparing female KO versus male KO. Our in vitro autoradiography demonstrates that M4 MR proportion represents 24% in the motor cortex (MOCx), 30% in the somatosensory cortex, 50% in the striatum, 69% in the thalamus, and 48% in the intergeniculate leaflet (IGL). The M4 MR densities were negligible in the subparaventricular zone, the posterior hypothalamic area, and in the suprachiasmatic nuclei.

CONCLUSIONS

We conclude that cholinergic signaling at M4 MR in brain structures such as striatum, MOCx, and probably with the important participation of IGL significantly control motor activity biorhythm. Animal activity differs in the light and dark phases, which should be taken into consideration when interpreting the results.

Application of an ex vivo cellular model of circadian variation for bipolar disorder research: a proof of concept study

OBJECTIVES

Disruption of circadian function has been observed in several human disorders, including bipolar disorder (BD). Research into these disorders can be facilitated by human cellular models that evaluate external factors (zeitgebers) that impact circadian pacemaker activity. Incorporating a firefly luciferase reporter system into human fibroblasts provides a facile, bioluminescent readout that estimates circadian phase, while leaving the cells intact. We evaluated whether this system can be adapted to clinical BD research and whether it can incorporate zeitgeber challenge paradigms.

METHODS

Fibroblasts from patients with bipolar I disorder (BD-I) (n = 13) and controls (n = 12) were infected ex vivo with a lentiviral reporter incorporating the promoter sequences for Bmal1, a circadian gene to drive expression of the firefly luciferase gene. Following synchronization, the bioluminescence was used to estimate period length. Phase response curves (PRCs) were also generated following forskolin challenge and the phase response patterns were characterized.

RESULTS

Period length and PRCs could be estimated reliably from the constructs. There were no significant case-control differences in period length, with a nonsignificant trend for differences in PRCs following the phase-setting experiments.

CONCLUSIONS

An ex vivo cellular fibroblast-based model can be used to investigate circadian function in BD-I. It can be generated from specific individuals and this could usefully complement ongoing circadian clinical research.

Identification of store-independent and store-operated Ca2+ conductances in Caenorhabditis elegans intestinal epithelial cells

The nematode Caenorhabditis elegans offers significant experimental advantages for defining the genetic basis of diverse biological processes. Genetic and physiological analyses have demonstrated that inositol-1,4,5-trisphosphate (IP3)-dependent Ca2+ oscillations in intestinal epithelial cells play a central role in regulating the nematode defecation cycle, an ultradian rhythm with a periodicity of 45-50 s. Patch clamp studies combined with behavioral assays and forward and reverse genetic screening would provide a powerful approach for defining the molecular details of oscillatory Ca2+ signaling. However, electrophysiological characterization of the intestinal epithelium has not been possible because of its relative inaccessibility. We developed primary intestinal epithelial cell cultures that circumvent this problem. Intestinal cells express two highly Ca2+-selective, voltage-independent conductances. One conductance, IORCa, is constitutively active, exhibits strong outward rectification, is 60-70-fold more selective for Ca2+ than Na+, is inhibited by intracellular Mg2+ with a K1/2 of 692 microM, and is insensitive to Ca2+ store depletion. Inhibition of IORCa with high intracellular Mg2+ concentrations revealed the presence of a small amplitude conductance that was activated by passive depletion of intracellular Ca2+ stores. Active depletion of Ca2+ stores with IP3 or ionomycin increased the rate of current activation approximately 8- and approximately 22-fold compared with passive store depletion. The store-operated conductance, ISOC, exhibits strong inward rectification, and the channel is highly selective for Ca2+ over monovalent cations with a divalent cation selectivity sequence of Ca2+ > Ba2+ approximately Sr2+. Reversal potentials for ISOC could not be detected accurately between 0 and +80 mV, suggesting that PCa/PNa of the channel may exceed 1,000:1. Lanthanum, SKF 96365, and 2-APB inhibit both IORCa and ISOC reversibly. Our studies provide the first detailed electrophysiological characterization of voltage-independent Ca2+ conductances in C. elegans and form the foundation for ongoing genetic and molecular studies aimed at identifying the genes that encode the intestinal cell channels, for defining mechanisms of channel regulation and for defining their roles in oscillatory Ca2+ signaling.