Vacuolar protein sorting 35 (VPS35) is a core component of the retromer trimer required for endosomal membrane-associated protein trafficking. The discovery of a missense mutation, Vps35 p.D620N implicates retromer dysfunction in the pathogenesis of Parkinson’s disease (PD). We have characterized a knock-in mouse with a Vps35 p.D620N substitution (hereafter referred to as VKI) at 3 months of age. Standardized behavioral testing did not observe overt movement disorder. Tyrosine hydroxylase (TH)-positive nigral neuron counts and terminal expression in striata were comparable across genotypes. Fast scan cyclic voltammetry revealed increased dopamine release in VKI striatal slices. While extracellular dopamine collected via striatal microdialysis of freely moving animals was comparable across genotypes, the ratio of dopamine metabolites to dopamine suggests increased dopamine turnover in VKI homozygous mice. Western blot of striatal proteins revealed a genotype-dependent decrease in dopamine transporter (DAT) along with an increase in vesicular monoamine transporter 2 (VMAT2), albeit independent of changes in other synaptic markers. The reduction in DAT was further supported by immunohistochemical analysis. The data show that the dopaminergic system of VKI mice is profoundly altered relative to wild-type littermates. We conclude early synaptic dysfunction contributes to age-related pathophysiology in the nigrostriatal system that may lead to parkinsonism in man.

液泡蛋白分选35（VPS35）是内体膜相关蛋白运输所需的三聚体三聚体的核心组成部分。Vps35 p.D620N错义突变的发现暗示了帕金森氏病（PD）发病机制中的后体功能障碍。我们已经对带有Vps35的敲入式鼠标进行了表征在3个月大时用p.D620N替代（以下称为VKI）。标准化的行为测试未观察到明显的运动障碍。酪氨酸羟化酶（TH）阳性黑质神经元计数和纹状体中的终端表达是跨基因型可比。快速扫描循环伏安法显示VKI纹状体切片中多巴胺释放增加。尽管通过自由活动的动物的纹状体微透析收集的细胞外多巴胺在各基因型上具有可比性，但多巴胺代谢产物与多巴胺的比率表明在VKI纯合小鼠中多巴胺周转率增加。纹状体蛋白的蛋白质印迹显示多巴胺转运蛋白（DAT）的基因型依赖性减少以及水泡单胺转运蛋白2（VMAT2）的增加，尽管与其他突触标记的变化无关。免疫组织化学分析进一步支持了DAT的降低。数据显示，相对于野生型同窝仔，VKI小鼠的多巴胺能系统发生了深远的变化。我们得出结论，早期突触功能障碍有助于黑质纹状体系统中与年龄相关的病理生理，这可能导致人发生帕金森氏病。