POLR1C variants dysregulate splicing and cause hypomyelinating leukodystrophy.
POLR1C variants dysregulate splicing and cause hypomyelinating leukodystrophy.
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DOI：
10.1212/nxg.0000000000000524
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发表时间：
2020-12
期刊：
影响因子：
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通讯作者：
Inoue K
中科院分区：
文献类型：
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作者：
Kashiki H;Li H;Miyamoto S;Ueno H;Tsurusaki Y;Ikeda C;Kurata H;Okada T;Shimazu T;Imamura H;Enomoto Y;Takanashi JI;Kurosawa K;Saitsu H;Inoue K
进一步阐明细胞水平上由双等位基因POLR1C变体引起的RNA聚合酶III（Pol III）相关脑白质营养不良的分子发病机制及其对下游基因的潜在影响。外显子组分析和分子功能研究，使用细胞表达和长读序分析进行了1个家庭与髓鞘形成不足的脑白质营养不良显示没有临床和MRI表现的特点Pol III相关的脑白质营养不良以外的髓鞘形成不足。双等位基因新POLR1C改变，c.167T>A，p.M56K和c.595A>T，p.I199F，被鉴定为致病变体。功能分析表明，这些变体不仅导致蛋白质亚细胞定位改变和蛋白质表达降低，而且还导致患者细胞中85%的POLR1C转录物中包含异常内含子。出乎意料的是，等位基因分离分析，在每个载体的父母揭示，每个杂合变异也导致包括内含子的突变体和野生型等位基因。这些发现表明，异常剪接不是变异体的直接后果，而是反映了变异体在POLR1C和潜在的其他靶基因的剪接失调中的下游效应。缺乏特征性的临床表现，在这个家庭证实了广泛的临床谱Pol III相关脑白质营养不良。分子研究表明，剪接的失调是POLR1C变异体的潜在下游病理机制。
To further clarify the molecular pathogenesis of RNA polymerase III (Pol III)-related leukodystrophy caused by biallelic POLR1C variants at a cellular level and potential effects on its downstream genes. Exome analysis and molecular functional studies using cell expression and long-read sequencing analyses were performed on 1 family with hypomyelinating leukodystrophy showing no clinical and MRI findings characteristic of Pol III–related leukodystrophy other than hypomyelination. Biallelic novel POLR1C alterations, c.167T>A, p.M56K and c.595A>T, p.I199F, were identified as causal variants. Functional analyses showed that these variants not only resulted in altered protein subcellular localization and decreased protein expression but also caused abnormal inclusion of introns in 85% of the POLR1C transcripts in patient cells. Unexpectedly, allelic segregation analysis in each carrier parent revealed that each heterozygous variant also caused the inclusion of introns on both mutant and wild-type alleles. These findings suggest that the abnormal splicing is not direct consequences of the variants, but rather reflect the downstream effect of the variants in dysregulating splicing of POLR1C, and potentially other target genes. The lack of characteristic clinical findings in this family confirmed the broad clinical spectrum of Pol III–related leukodystrophy. Molecular studies suggested that dysregulation of splicing is the potential downstream pathomechanism for POLR1C variants.