CANAVAN DISEASE: SUPPRESSING THE PHENOTYPE BY INHIBITING NAA SYNTHESIS

CANAVAN 病：通过抑制 NAA 合成来抑制表型

• 批准号: 8965565
• 负责人: David E. Pleasure
• 金额: $ 23.48万
• 依托单位: UNIVERSITY OF CALIFORNIA AT DAVIS
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-15 至 2017-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8965565
• 关键词: Abbreviations; Acetate-CoA Ligase; Acetates; Acetyl Coenzyme A; Actins; Alleles; Amino Acids; Aspartate; Aspartoacylase; Brain; Brain Stem; Breeding; Canavan Disease; Chickens; Child; Childhood; Cleaved cell; Data; Diagnosis; Diet; Disease; Enhancers; Enzymes; Evaluation; Family; Genetic Recombination; Heterozygote; Human; Inborn Genetic Diseases; Intervention; Knock-out; Knockout Mice; Leukoencephalopathy; Lipids; LoxP-flanked allele; Magnetic Resonance Spectroscopy; Metabolism; Modeling; Mus; Mutation; Myelin; N-acetylaspartate; Nervous System Physiology; Neurologic; Neurons; Oligodendroglia; Onset of illness; Phenotype; Prion Diseases; Prosencephalon; Radiolabeled; Rattus; Recording of previous events; Rodent; Source; Starvation; Synthetic Genes; Tamoxifen; Testing; Therapeutic; Transgenes; astrogliosis; dicarboxylate-binding protein; dietary supplements; dysmyelination; early onset; human NAT2 protein; infancy; innovation; myelination; novel therapeutic intervention; prevent; promoter; public health relevance; radiotracer; young adult

 DESCRIPTION (provided by applicant): Canavan disease is a recessively inherited disorder caused by inactivating aspartoacylase (ASPA) mutations and characterized by forebrain, cerebellar, and brainstem vacuolar degeneration, astrogliosis, and dysmyelination ("spongiform leukodystrophy"). No treatments for children with Canavan disease have yet proven effective. ASPA is an oligodendroglial enzyme that cleaves N-acetyl-L-aspartate (NAA), releasing acetate and L-aspartate. NAA is synthesized by the neuronal enzyme N-acetyltransferase-8 like (NAT8L), and is maintained at approximately 10mM in the normal CNS, but in Canavan disease, CNS NAA climbs far above that level. A popular hypothesis is that acetate released from NAA and converted to acetyl-CoA by oligodendroglial acetyl-CoA synthetase is essential to maintain the oligodendroglial lipogenic acetyl-CoA pool, and that spongiform leukodystrophy in Canavan disease is attributable to oligodendroglial acetyl-CoA "starvation". But our preliminary data challenge the necessity for NAA-derived acetate for CNS myelin lipid synthesis by showing that, in the CNS of homozygous constitutive NAT8L knockout (NAT8LKO/KO) mice, in which NAA is undetectable by 1H-magnetic resonance spectroscopy, acetyl-CoA content and myelination are normal. Specific Aim 1 will evaluate an alternative hypothesis, that spongiform leukodystrophy in Canavan disease is a consequence of persistently elevated CNS concentrations of NAA. We will employ a well characterized mouse Canavan model caused by homozygosity for a nonsense ASPA mutation (ASPAnur7). By crossing mice carrying ASPAnur7 and NAT8LKO alleles, ASPAnur7/nur7 mice carrying 2, 1, or 0 NAT8LKO alleles will be generated, and will be used to test the prediction that suppressing NAA synthesis in ASPAnur7/nur7 mice will prevent spongiform leukodystrophy. In Specific Aim 2, we will administer tamoxifen to symptomatic young adult ASPAnur7/nur7 mice that are homozygous for a conditional NAT8L allele (NAT8Lflox) and carrying a widely expressed tamoxifen-inducible cre transgene to test whether delayed suppression of NAA synthesis will reverse their pre-existing spongiform leukodystrophy. If so, interventions to prevent elevated CNS NAA levels in children with Canavan disease may be of therapeutic value.

 描述（由申请人提供）：卡纳万病是一种由失活乙酰化酶（ASPA）突变引起的复发性遗传性疾病，其特征为前脑、小脑和脑干空泡变性、星形胶质细胞增生和髓鞘形成障碍（“海绵状脑白质营养不良”）。目前还没有针对Canavan病儿童的有效治疗方法。ASPA是一种少突神经胶质酶，可切割N-乙酰基-L-天冬氨酸（NAA），释放乙酸和L-天冬氨酸。NAA由神经元酶N-乙酰转移酶-8样（NAT 8L）合成，并且在正常CNS中维持在约10 mM，但在卡纳万病中，CNS NAA攀升远高于该水平。一个流行的假设是，乙酸释放的NAA和转化为乙酰辅酶A的少突胶质细胞乙酰辅酶A合成酶是必不可少的，以维持少突胶质细胞脂肪生成乙酰辅酶A池，海绵状脑白质营养不良的卡纳万病是由于少突胶质细胞乙酰辅酶A的“饥饿”。但是我们的初步数据挑战了NAA衍生的乙酸盐用于CNS髓鞘脂质合成的必要性，其显示，在纯合组成型NAT 8L敲除（NAT 8LKO/KO）小鼠的CNS中，其中NAA通过1H-磁共振光谱检测不到，乙酰辅酶A含量和髓鞘形成是正常的。具体目标1将评估另一种假设，即海绵状脑白质营养不良在卡纳万病是一个持续升高的CNS浓度的NAA的结果。我们将采用由无义ASPA突变（ASPAnur 7）的纯合性引起的充分表征的小鼠Canavan模型。通过使携带ASPAnur 7和NAT 8LKO等位基因的小鼠杂交，将产生携带2、1或0个NAT 8LKO等位基因的ASPAnur 7/nur 7小鼠，并将其用于测试抑制ASPAnur 7/nur 7小鼠中的NAA合成将预防海绵状脑白质营养不良的预测。在具体目标2中，我们将给有症状的年轻成年ASPAnur 7/nur 7小鼠施用他莫昔芬，这些小鼠是条件性NAT 8L等位基因（NAT 8Lflox）纯合子，并携带广泛表达的他莫昔芬诱导型cre转基因，以测试延迟抑制NAA合成是否会逆转其先前存在的海绵状脑白质营养不良。如果是这样，干预措施，以防止与卡纳万病的儿童中枢神经系统NAA水平升高可能是有治疗价值的。