We previously reported on two brothers who carry identical compound heterozygous PRKN mutations yet present with significantly different Parkinson’s Disease (PD) clinical phenotypes. Juvenile cases demonstrate that PD is not necessarily an aging-associated disease. Indeed, evidence for a developmental component to PD pathogenesis is accumulating. Thus, we hypothesized that the presence of additional genetic modifiers, including genetic loci relevant to mesencephalic dopamine neuron development, could potentially contribute to the different clinical manifestations of the two brothers. We differentiated human-induced pluripotent stem cells (hiPSCs) derived from the two brothers into mesencephalic neural precursor cells and early postmitotic dopaminergic neurons and performed wholeexome sequencing and transcriptomic and metabolomic analyses. No significant differences in the expression of canonical dopamine neuron differentiation markers were observed. Yet our transcriptomic analysis revealed a significant downregulation of the expression of three neurodevelopmentally relevant cell adhesion molecules, CNTN6, CNTN4 and CHL1, in the cultures of the more severely affected brother. In addition, several HLA genes, known to play a role in neurodevelopment, were differentially regulated. The expression of EN2, a transcription factor crucial for mesencephalic dopamine neuron development, was also differentially regulated. We further identified differences in cellular processes relevant to dopamine metabolism. Lastly, wholeexome sequencing, transcriptomics and metabolomics data all revealed differences in glutathione (GSH) homeostasis, the dysregulation of which has been previously associated with PD. In summary, we identified genetic differences which could potentially, at least partially, contribute to the discordant clinical PD presentation of the two brothers.

我们之前报道过两兄弟携带相同的复合杂合PRKN突变，但表现出显着不同的帕金森病 (PD) 临床表型。青少年病例表明帕金森病不一定是一种与衰老相关的疾病。事实上，关于帕金森病发病机制中发育因素的证据正在不断积累。因此，我们假设额外遗传修饰剂的存在，包括与中脑多巴胺神经元发育相关的遗传位点，可能导致两兄弟的不同临床表现。我们将源自两兄弟的人诱导多能干细胞 (hiPSC) 分化为中脑神经前体细胞和早期有丝分裂后多巴胺能神经元，并进行全外显子组测序以及转录组学和代谢组学分析。没有观察到典型多巴胺神经元分化标记物的表达存在显着差异。然而，我们的转录组分析显示，在受影响更严重的兄弟的培养物中，三种神经发育相关的细胞粘附分子CNTN6 、 CNTN4和CHL1的表达显着下调。此外，一些已知在神经发育中发挥作用的HLA基因也受到了差异性调节。 EN2 （一种对中脑多巴胺神经元发育至关重要的转录因子）的表达也受到差异调节。我们进一步确定了与多巴胺代谢相关的细胞过程的差异。最后，全外显子组测序、转录组学和代谢组学数据都揭示了谷胱甘肽 (GSH) 稳态的差异，其失调先前已被认为与帕金森病有关。 总之，我们发现遗传差异可能（至少部分地）导致两兄弟的 PD 临床表现不一致。