PT608. Analysis of glutamate-induced processing of proline-rich transmembrane protein 2 (PRRT2)

s | 269 the number, mean duration and total duration of spike wave discharges (SWD) were evaluated using EEG recordings. Each group was then divided into two subgroups. In the first group mean arterial blood pressure (MAP) and heart rate (HR) measurements were performed. In the second group, in vitro isolated organ studies were conducted on the thoracic aortas of animals. Results: ETX treatment significantly reduced the number, mean duration and total duration of SWDs in WAG/Rij rats compared to control group. Wistar groups did not have any SWD. In WAG/ Rij control group, MAP was significantly higher than Wistar control. HR in Wistar ETX group was significantly lower than Wistar control group. KCl contraction responses increased in the Wistar ETX and decreased in the WAG/Rij control group compared to Wistar control group. Carbachol relaxation responses significantly increased in WAG/Rij control and decreased in Wistar ETX group compared to Wistar control group. There was no significant difference in sodium nitroprusside responses. Conclusions: Cardiovascular function changes have been observed in the WAG/Rij rats with AE and as a result of ethosuximide treatment, indicating that T-type calcium channels may play a major role in these changes. This abstract was supported by TÜBİTAK within the scope of the project numbered 114S481. PT607 Effect of Neural Stem Cell Transplantation on Absence Seizures in Genetic Absence Epileptic WAG/ Rij Rats Tijen Utkan1, Tuğçe Demirtaş Şahin1, Ayşe Karson2, Zehra Seda Halbutoğulları3, Yusufhan Yazır3 1Kocaeli University Medical Faculty, Pharmacology Department, Kocaeli, Turkey 2Kocaeli University Medical Faculty, Physiology Department, Kocaeli, Turkey 3Kocaeli University Medical Faculty, Stem Cell and Gene Therapies Research & Applied Center, Kocaeli, Turkey Abstract Objective: Absence epilepsy is characterized by spike-wave discharges (SWD) that are thought to be generated due to abnormal synchronization of cortico-thalamo-cortical networks. Although the pathophysiology of the disease remains uncertain, some evidence showed that absence seizures may be partially linked to reduced GABAergic neurotransmission. The WAG/Rij strain ofObjective: Absence epilepsy is characterized by spike-wave discharges (SWD) that are thought to be generated due to abnormal synchronization of cortico-thalamo-cortical networks. Although the pathophysiology of the disease remains uncertain, some evidence showed that absence seizures may be partially linked to reduced GABAergic neurotransmission. The WAG/Rij strain of rats is a well-established genetic model for absence epilepsy. In this study we aimed to investigate the efficacy of neural stem cell (NSC) treatment on absence seizures in WAG/Rij rats with genetic absence epilepsy. Method: We divided 2 month old Wistar and WAG/Rij rats into three groups (n=10): Control, NSC and sham. NSCs taken from fetal medial ganglionic eminence (MGE) were transplanted into perioral regions of the primary somatosensory cortex (S1po) of NSC groups and we waited for 3 months for cell differentiation. We determined the cell differentiation into neurons, astrocytes, oligodendrocytes and GABAergic neurons in vitro. At the end of 3 months; the number, mean duration and total duration of SWDs were evaluated using EEG recordings. Results: MGE-derived NSCs were found to differentiate into astrocytes, neurons, oligodendrocytes and GABAergic neurons in vitro. All Wistar groups did not have any SWD during EEG recordings. NSC treatment significantly reduced the number, mean duration and total duration of SWDs in WAG/Rij rats compared to control and sham groups (p<0.05). No significant changes related to seizure activity were observed between control and sham groups in WAG/Rij rats. Conclusions: Our findings suggest that transplantation of GABAergic neurons into the S1po, a brain region that is thought to be responsible for the initiation of the SWDs in absence epilepsy, reduced absence seizures in WAG/Rij rats. NSC treatment may be a potential alternative to conventional antiepileptic drug therapy in absence epilepsy. This abstract was supported by TÜBİTAK within the scope of the project numbered 114S481. PT608 Analysis of glutamate-induced processing of prolinerich transmembrane protein 2 (PRRT2) Daisuke Hatta1, Keisuke Kajiyama1, Naohiro Kurotaki2, Hiroki Ozawa2, Masashi Asai1, Keiro Shirotani1, Nobuhisa Iwata1 1Department of Genome-based Drug Discovery, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan 2Department of Neuropsychiatry, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan Abstract PKD (paroxysmal kinesigenic dyskinesia) is an autosomal dominant disorder characterized by brief but frequent attacksPKD (paroxysmal kinesigenic dyskinesia) is an autosomal dominant disorder characterized by brief but frequent attacks triggered by involuntary sudden movements, and is often misdiagnosed as common epilepsy. PRRT2 (proline-rich transmembrane protein 2) was identified as a causative gene of familial PKD in 2011 (1, 2), and almost all PKD-linked PRRT2 gene mutations bring a lack of two C-terminal transmembrane regions of PRRT2 proteins, resulting in their subcellular mislocalization in neurons. Therefore, a cause of PKD is supposed to be loss of functions of PRRT2, although its physiological functions are poorly understood. However, PRRT2 may be implicated in neuronal hyperexcitability, as it was reported that PRRT2 interacted with GluR1, a subunit of AMPA receptor (3). In this study we investigated a neuronal activity-dependent processing of PRRT2 during neuronal excitation. When we treated mouse cortical primary neurons with glutamate, we found that PRRT2 was processed immediately after the neuronal excitation and a 15 kDa fragment was generated. Since the fragment was detected in membrane fraction, not in cytosolic fraction, the fragment includes the C-terminal transmembrane regions of PRRT2. To identify proteases responsible for this processing, we treated neurons with various protease inhibitors together with glutamate. We found that generation of the fragment was inhibited by a serine protease inhibitor leupeptin. Because generation of the 15 kDa C-terminal fragment (15K-CTF) is induced by glutamate, it may be involved in regulation of activity-dependent neuronal excitability. Given that many mutants of PRRT2 linked to PKD lack the C-terminal transmembrane regions of PRRT2, the processing is required for physiological functions of neurons, the 15K-CTF may play a critical role in limited functions of PRRT2. We are currently analyzing exact pathophysiological functions of the 15K-CTF as well as full-length PRRT2. (279 words →281)