Recently, an African ancestry-specific Parkinson disease (PD) risk signal was identified at the gene encoding glucocerebrosidase (GBA1). This variant (rs3115534-G) is carried by ~50% of West African PD cases and imparts a dose-dependent increase in risk for disease. The risk variant has varied frequencies across African ancestry groups but is almost absent in European and Asian ancestry populations. GBA1 is a gene of high clinical and therapeutic interest. Damaging biallelic protein-coding variants cause Gaucher disease and monoallelic variants confer risk for PD and dementia with Lewy bodies, likely by reducing the function of glucocerebrosidase. Interestingly, the African ancestry-specific GBA1 risk variant is a noncoding variant, suggesting a different mechanism of action. Using full-length RNA transcript sequencing, we identified partial intron 8 expression in risk variant carriers (G) but not in nonvariant carriers (T). Antibodies targeting the N terminus of glucocerebrosidase showed that this intron-retained isoform is likely not protein coding and subsequent proteomics did not identify a shorter protein isoform, suggesting that the disease mechanism is RNA based. Clustered regularly interspaced short palindromic repeats editing of the reported index variant (rs3115534) revealed that this is the sequence alteration responsible for driving the production of these transcripts containing intron 8. Follow-up analysis of this variant showed that it is in a key intronic branchpoint sequence and, therefore, has important implications in splicing and disease. In addition, when measuring glucocerebrosidase activity, we identified a dose-dependent reduction in risk variant carriers. Overall, we report the functional effect of a GBA1 noncoding risk variant, which acts by interfering with the splicing of functional GBA1 transcripts, resulting in reduced protein levels and reduced glucocerebrosidase activity. This understanding reveals a potential therapeutic target in an underserved and underrepresented population.

最近，在编码葡萄糖脑苷脂酶 （GBA1） 的基因中鉴定出非洲血统特异性帕金森病 （PD） 风险信号。这种变体 （rs3115534-G） 由 ~50% 的西非 PD 病例携带，并导致疾病风险呈剂量依赖性增加。这种风险变异在非洲血统群体中发生的频率各不相同，但在欧洲和亚洲血统人群中几乎不存在。GBA1 是一个具有高度临床和治疗价值的基因。破坏性双等位基因蛋白编码变异导致戈谢病，单等位基因变异可能通过降低葡萄糖脑苷脂酶的功能赋予路易体 PD 和痴呆的风险。有趣的是，非洲血统特异性 GBA1 风险变异是一种非编码变异，表明存在不同的作用机制。使用全长 RNA 转录本测序，我们在风险变异携带者 （G） 中鉴定了部分内含子 8 表达，但在非变异携带者 （T） 中没有。靶向葡萄糖脑苷脂酶 N 末端的抗体显示，这种内含子保留的亚型可能不是蛋白质编码，随后的蛋白质组学没有鉴定出较短的蛋白质亚型，这表明疾病机制是基于 RNA 的。对已报道的索引变体 （rs3115534） 的成簇规则间隔短回文重复编辑显示，这是负责驱动这些包含内含子 8 的转录本产生的序列改变。对该变体的后续分析表明，它位于关键的内含子分支点序列中，因此在剪接和疾病中具有重要意义。此外，在测量葡萄糖脑苷脂酶活性时，我们确定了风险变异携带者的剂量依赖性降低。 总体而言，我们报道了 GBA1 非编码风险变体的功能效应，该变体通过干扰功能性 GBA1 转录本的剪接发挥作用，导致蛋白质水平降低和葡萄糖脑苷脂酶活性降低。这种理解揭示了服务不足和代表性不足的人群的潜在治疗靶点。