背景:在波士顿儿童医院智力和发育障碍研究中心(IDDRC)的转化研究中,琥珀酸半醛脱氢酶缺乏症(SSADHD)代表了一种模型神经代谢疾病,包括NIH赞助的临床自然史研究,神经生理学,神经影像学,和分子标记,患者来源的诱导多能干细胞(iPSC)表征,和一个严格调控的鼠模型的发展,细胞特异性基因治疗。
方法:SSADHD受试者接受临床评估,神经心理学评估,γ-氨基丁酸(GABA)和相关代谢物的生化定量,脑电图(标准和高密度),脑磁图,经颅磁刺激,磁共振成像和光谱学,和基因测试。这与SSADHD受试者的诱导人多能干细胞(hiPSC)衍生的体外GABA能神经元的实验室分子研究以及在通用鼠模型上进行的生化分析平行,该模型使用可诱导和可逆的挽救策略,允许按需和细胞特异性基因治疗。
结果:62名SSADHD受试者[53%为女性,纳入研究的中位年龄(IQR)为9.6(5.4-14.5)岁]在~6个月时报告出现症状,且诊断的中位年龄为4岁.语言发育迟缓比运动更突出。自闭症,癫痫,运动障碍,睡眠障碍,各种精神行为构成了该疾病临床表型的核心。较低的临床严重程度评分,表示严重程度最差,与年龄相同(R=-0.302,p=0.03),以及年龄调整后的血浆γ-氨基丁酸酯(GABA)(R=0.337,p=0.02)和γ-羟基丁酸酯(GHB)(R=0.360,p=0.05)的较低值。虽然癫痫和精神行为的严重程度随着年龄的增长而增加,沟通能力和运动功能趋于改善。iPSC,分化为GABA能神经元,代表SSADHD的第一个体外神经元模型,并表达神经元标记微管相关蛋白2(MAP2),以及GABA。使用CRISPR校正致病变体或mRNA转染可以逆转诱导的GABA能神经元中的GABA代谢,并且SSADHDiPSCs与过量的谷氨酸能活性和相关的突触兴奋有关。
结论:来自SSADHD自然历史研究的结果与iPSC和动物模型研究集中在我们IDDRC中的常见疾病上,加深我们对复杂神经发育障碍的病理生理学和纵向临床过程的了解。这进一步使得能够在整个开发过程中识别生物标志物和变化,这对于即将进行的酶替代和基因治疗的靶向试验至关重要。
BACKGROUND: Succinic semialdehyde dehydrogenase deficiency (SSADHD) represents a model neurometabolic disease at the fulcrum of translational research within the Boston Children\'s Hospital Intellectual and Developmental Disabilities Research Centers (IDDRC), including the NIH-sponsored natural history
study of clinical, neurophysiological, neuroimaging, and molecular markers, patient-derived induced pluripotent stem cells (iPSC) characterization, and development of a murine model for tightly regulated, cell-specific gene therapy.
METHODS: SSADHD subjects underwent clinical evaluations, neuropsychological assessments, biochemical quantification of γ-aminobutyrate (GABA) and related metabolites, electroencephalography (standard and high density), magnetoencephalography, transcranial magnetic stimulation, magnetic resonance imaging and spectroscopy, and genetic tests. This was parallel to laboratory molecular investigations of in vitro GABAergic neurons derived from induced human pluripotent stem cells (hiPSCs) of SSADHD subjects and biochemical analyses performed on a versatile murine model that uses an inducible and reversible rescue strategy allowing on-demand and cell-specific gene therapy.
RESULTS: The 62 SSADHD subjects [53% females, median (IQR) age of 9.6 (5.4-14.5) years] included in the
study had a reported symptom onset at ∼ 6 months and were diagnosed at a median age of 4 years. Language developmental delays were more prominent than motor. Autism, epilepsy, movement disorders, sleep disturbances, and various psychiatric behaviors constituted the core of the disorder\'s clinical phenotype. Lower clinical severity scores, indicating worst severity, coincided with older age (R= -0.302, p = 0.03), as well as age-adjusted lower values of plasma γ-aminobutyrate (GABA) (R = 0.337, p = 0.02) and γ-hydroxybutyrate (GHB) (R = 0.360, p = 0.05). While epilepsy and psychiatric behaviors increase in severity with age, communication abilities and motor function tend to improve. iPSCs, which were differentiated into GABAergic neurons, represent the first in vitro neuronal model of SSADHD and express the neuronal marker microtubule-associated protein 2 (MAP2), as well as GABA. GABA-metabolism in induced GABAergic neurons could be reversed using CRISPR correction of the pathogenic variants or mRNA transfection and SSADHD iPSCs were associated with excessive glutamatergic activity and related synaptic excitation.
CONCLUSIONS: Findings from the SSADHD Natural History
Study converge with iPSC and animal model work focused on a common disorder within our IDDRC, deepening our knowledge of the pathophysiology and longitudinal clinical course of a complex neurodevelopmental disorder. This further enables the identification of biomarkers and changes throughout development that will be essential for upcoming targeted trials of enzyme replacement and gene therapy.