Table 2_Mutation in Wdr45 leads to early motor dysfunction and widespread aberrant axon terminals in a beta-propeller protein associated neurodegeneration (BPAN) patient-inspired mouse model.xlsx

Beta-propeller Protein Associated Neurodegeneration (BPAN) is a devastating neurodevelopmental and neurodegenerative disease linked to variants in WDR45. Currently, there is no cure or disease altering treatment for this disease. This is, in part, due to a lack of insight into early phenotypes of BPAN progression and WDR45’s role in establishing and maintaining neurological function. Here we generated and characterized a mouse model bearing a c52C > T BPAN patient variant in Wdr45. We show this mutation ablates WDR45 protein expression and alters autophagy in the brain. Behavioral analysis of these mice revealed characteristic signs of BPAN including cognitive impairment, hyperactivity, and motor decline. We show these behaviors coincide with widespread glial activation and early development of axonal spheroids in multiple neuron subclasses throughout the brain. Several lines of evidence suggest these spheroids arise from axon terminals. Transcriptomic analysis uncovered multiple disrupted pathways in the cortex including genes associated with synapses, neurites, endosomes, endoplasmic reticulum, and ferroptosis. This is supported by accumulation of the iron regulating transferrin receptor 1 (TFRC) and the endoplasmic reticulum resident calreticulin (CALR) in the cortex as these animals age. CALR forms spheroid structures similar to the axonal spheroids seen in these animals. Taken together, our data suggest that WDR45 is necessary for healthy brain function and maintenance of axon terminals. This model opens the door to therapeutics targeting BPAN and further exploration of the role of WDR45 in neuronal function.

β螺旋蛋白相关神经退行性疾病（Beta-propeller Protein Associated Neurodegeneration, BPAN）是一类毁灭性的神经发育与神经退行性疾病，其发病与WDR45基因的变异密切相关。目前针对该疾病尚无治愈方案或可改变疾病进程的治疗手段，究其根源，部分在于我们对BPAN进展的早期表型以及WDR45在构建并维持神经系统功能中的作用仍缺乏深入认知。本研究构建并鉴定了一种携带Wdr45基因c.52C>T（BPAN患者致病变异）的小鼠模型。研究发现，该突变可完全消除WDR45蛋白的表达，并改变大脑内的自噬过程。对该小鼠的行为学分析显示，其出现了BPAN的特征性症状：认知障碍、活动过度以及运动功能衰退。进一步研究表明，此类行为异常与大脑多神经元亚群中广泛的胶质细胞激活，以及轴突球状体的早期形成高度契合。多项证据显示，此类轴突球状体起源于轴突末梢。转录组学分析揭示，小鼠大脑皮层内多条通路出现紊乱，涉及突触、神经突、内体、内质网以及铁死亡相关的基因。随着小鼠年龄增长，大脑皮层中铁调节相关的转铁蛋白受体1（transferrin receptor 1, TFRC）与内质网驻留蛋白钙网蛋白（calreticulin, CALR）的积累进一步验证了上述结论。CALR可形成与该小鼠体内观察到的轴突球状体结构相似的聚集体。综上，本研究数据表明WDR45对于维持大脑正常功能及轴突末梢稳态至关重要。该小鼠模型为BPAN靶向治疗药物的研发以及进一步探究WDR45在神经元功能中的作用提供了关键研究平台。