Oral Session

Oral Session 1 一般口演1

O1-1 Impaired fatty aldehyde oxidation in a gene knockout mouse model of Sjogren-Larsson syndrome is associated with behavioral abnormalities and reduced myelin 2-hydroxygalactosylceramide levels 脂肪族アルデヒド代謝障害を示すシェーグレン・ラルソン症候群モデルマウスにおける行動異常とミエリンの2-水酸化ガラクトシルセラミドの減少 Sassa Takayuki（佐々貴之），金武司，野尻光希，北村拓也，木原章雄 Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University Sjogren-Larsson syndrome (SLS) is an autosomal recessive neurocutaneous disorder characterized by ichthyosis, mental retardation, and spasticity. SLS is caused by mutations in the ALDH3A2 gene, which encodes fatty aldehyde dehydrogenase. Although the fatty aldehydes accumulated in SLS patients are assumed to cause the pathology by attacking and inhibiting certain proteins important in skin and nervous systems, the target proteins remain to be identified. In the present study, we analyzed the neural phenotypes of Aldh3a2 knockout mice. Through a battery of behavioral tests, we observed several abnormalities which may be related to neurological symptoms of SLS. Biochemically, we found a significant decrease in the levels of 2-hydroxy (2-OH) galactosylceramide (GalCer), one of the major lipid species in myelin. The 2-OH GalCer contains 2-OH fatty acid (FA), which is synthesized by the FA 2-hydroxylase FA2H. We observed that the activity of FA2H was well correlated with that of ALDH3A2. By using mass spectrometry, we found that FA2H is conjugated with trans-2-hexadecenal, the fatty aldehyde formed during sphingolipid metabolism and oxidized by ALDH3A2, in histidine residues that are essential for its activity. Since mutations in the FA2H gene cause spastic paraplegia type 35 (SPG35), which exhibits neurological symptoms similar to those associated with SLS, the inactivation of FA2H by the fatty aldehydes, especially trans-2-hexadecenal, may be a key molecular basis of SLS pathogenesis.		O1-2 Pathophysiological analysis of inherited leukodystrophy with defective myeline lipid metabolism and its therapeutic application to the demyelinating diseases Myelin lipid 分解経路の破綻がもたらす脳白質障害の病態解析とその治療応用 Enokido Yasushi（榎戸靖）¹，鬼頭もも子²，郷慎司³，細川昌則¹，浅井清文²，竹林浩秀⁴，松田純子³，稲村直子¹ ¹Dept. of Pathol., Inst. of Dev. Res., Aichi Human Service Center ²Inst. Mol. Med. Grad. Sch. of Med., Nagoya City Univ. ³Dept. of Pathophys. & Metab, Kawasaki Med. Sch. ⁴Grad. Sch. of Med. and Dent. Sci., Niigata Univ. Myelin is a sheath-like structure wrapping around the nerve axon. It is formed by an electrically insulating membranes that allows to propagate saltatory conduction of nerve impulse. The primary lipid of myelin is a glycolipid called galactosylceramide (or galactocerebroside), which is catalyzed by a lysosomal enzyme galactosylceramidase (GALC). Mutations in GALC gene causes Krabbe disease (KD), one of the lysosomal storage diseases with inherited leukodystrophy. The majority of KD patients are characterized by infantile-onset cerebral demyelination with apoptotic oligodendrocyte (OL) death. Currently, there are no effective treatments for KD. In the present study, we investigated cellular mechanisms of pathogenic changes in developing KD OLs by using twitcher mice, an authentic mouse model of KD. In twitcher mouse brain, myelination was impaired, and the myelin gene and protein expression were significantly decreased when the period of active myelination prior to pathogenic demyelination. To investigate the differentiation and maturation of KD OLs in detail, we cultured primary OL precursor cells (OPCs) isolated from twitcher mouse brains. Interestingly, twitcher OPCs proliferated normally, but their differentiation and survival were intrinsically defective. These defects were associated with abnormally accumulated endogenous psychosine (galactosylsphingosine), and the reduced activation of some signaling pathways involved in OL differentiation and maturation.

O1-3 Increased ratio of large myelin protein zero (L-MPZ) in myelin leads to Charcot-Marie-Tooth disease like phenotype 髄鞘におけるlarge myelin protein zero（L-MPZ）の増加によるシャルコー・マリー・トゥース病様末梢神経障害の発生 Otani Yoshinori（大谷嘉典），山口宜秀，崔晶晶，馬場広子 Department of Molecular Neurobiology, Tokyo University of Pharmacy and Life Sciences, Hachioji, Japan Charcot-Marie-Tooth (CMT) disease is one of the hereditary motor and sensory neuropathies characterized by progressive motor and sensory disturbances especially in the extremities. CMT is mainly caused by mutations of Schwann cell myelin proteins such as peripheral myelin protein 22 (PMP22) and myelin protein zero (P0). L-MPZ is an isoform of P0, containing additional 63 amino acids at C-terminus by translational readthrough mechanism in various species including human (Yamaguchi et al., 2012). While L-MPZ is localized in the peripheral nerve system (PNS) myelin, a role of this protein is still uncertain. Our previous study showed that adhesion of L-MPZ property was less than P0, suggesting that L-MPZ and P0 (L-MPZ/P0) ratio in myelin may be important. To clarify physiological significance of L-MPZ/P0 ratio in the PNS, we generated a mouse line (L-MPZ mouse) that synthesizes only L-MPZ by CRISPR-Cas9 system. The motor test and morphological, immunohistological and electrophysiological analyses showed that L-MPZ mice caused peripheral neuropathy similar to CMT phenotype. Heterozygote mice those had increased L-MPZ and decreased P0 levels demonstrated various conditions from normal to neuropathy phenotypes. Thus, increased ratio of L-MPZ/P0 may cause CMT phenotype. Our study indicates a new possibility of CMT pathogenesis caused by alteration of the L-MPZ/P0 ratio.