PDF(Pubmed)
Abstract：
Creutzfeldt-Jakob Disease (CJD), the most common human prion disease, is associated with pathologic misfolding of the prion protein (PrP), encoded by the PRNP gene. Of human prion disease cases, ~1% were transmitted by misfolded PrP, ~15% are inherited, and ~85% are sporadic (sCJD). While familial cases are inherited through germline mutations in PRNP, the cause of sCJD is unknown. Somatic mutations have been hypothesized as a cause of sCJD, and recent studies have revealed that somatic mutations accumulate in neurons during aging. To investigate the hypothesis that somatic mutations in PRNP may underlie sCJD, we performed deep DNA sequencing of PRNP in 205 sCJD cases and 170 age-matched non-disease controls. We included 5 cases of Heidenhain variant sporadic CJD (H-sCJD), where visual symptomatology and neuropathology implicate focal initiation of prion formation, and examined multiple regions across the brain including in the affected occipital cortex. We employed Multiple Independent Primer PCR Sequencing (MIPP-Seq) with a median depth of >5,000X across the PRNP coding region and analyzed for variants using MosaicHunter. An allele mixing experiment showed positive detection of variants in bulk DNA at a variant allele fraction (VAF) as low as 0.2%. We observed multiple polymorphic germline variants among individuals in our cohort. However, we did not identify bona fide somatic variants in sCJD, including across multiple affected regions in H-sCJD, nor in control individuals. Beyond our stringent variant-identification pipeline, we also analyzed VAFs from raw sequencing data, and observed no evidence of prion disease enrichment for the known germline pathogenic variants P102L, D178N, and E200K. The lack of PRNP pathogenic somatic mutations in H-sCJD or the broader cohort of sCJD suggests that clonal somatic mutations may not play a major role in sporadic prion disease. With H-sCJD representing a focal presentation of neurodegeneration, this serves as a test of the potential role of clonal somatic mutations in genes known to cause familial neurodegeneration.
摘要：
克雅氏病（CJD），人类最常见的朊病毒病，与朊病毒蛋白（PrP）的病理性错误折叠有关，由PRNP基因编码。在人类朊病毒病病例中，1%是由错误的PrP传播的，15%是遗传的，85%是零星的(sCJD)。虽然家族病例是通过PRNP中的种系突变遗传的，sCJD的原因未知。体细胞突变被假设为sCJD的原因，最近的研究表明，体细胞突变在衰老过程中在神经元中积累。为了研究PRNP中的体细胞突变可能是sCJD的基础的假设，我们对205例sCJD病例和170例年龄匹配的非疾病对照进行了PRNP的深度DNA测序.我们纳入了5例Heidenhain变异散发性CJD（H-sCJD），其中视觉症状学和神经病理学暗示pr病毒形成的局灶性起始，并检查了整个大脑的多个区域，包括受影响的枕骨皮质。我们采用多重独立引物PCR测序(MIPP-Seq),其在整个PRNP编码区的中值深度>5,000X,并使用MosaicHunter分析变体。等位基因混合实验显示,在低至0.2%的变体等位基因分数(VAF)处,阳性检测到大量DNA中的变体。我们在我们的队列中观察到个体中的多个多态种系变异。然而,我们没有在sCJD中鉴定出真正的体细胞变异，包括H-sCJD中的多个受影响区域，也不能控制个人。除了我们严格的变体识别渠道，我们还从原始测序数据中分析了VAF，并且没有观察到已知种系致病变种P102L的朊病毒病富集的证据，D178N,和E200K。H-sCJD或更广泛的sCJD队列中缺乏PRNP致病性体细胞突变表明，克隆体细胞突变可能在散发性朊病毒疾病中没有发挥主要作用。H-sCJD代表神经变性的局灶性表现，这是对已知可导致家族性神经变性的基因中克隆体细胞突变的潜在作用的检验.
