Department of Neurogenetics, Massachusetts General Hospital and Program in Neuroscience, Harvard Medical School, Boston, Massachusetts, United States of America.
PLoS One. 2013 Oct 4;8(10):e76975. doi: 10.1371/journal.pone.0076975. eCollection 2013.
Mutations in the GCH1 gene are associated with childhood onset, dopa-responsive dystonia (DRD). Correct diagnosis of DRD is crucial, given the potential for complete recovery once treated with L-dopa. The majority of DRD associated mutations lie within the coding region of the GCH1 gene, but three additional single nucleotide sequence substitutions have been reported within the 5' untranslated (5'UTR) region of the mRNA. The biologic significance of these 5'UTR GCH1 sequence substitutions has not been analyzed.
METHODOLOGY/PRINCIPAL FINDINGS: Luciferase reporter assays, quantitative real time PCR and RNA decay assays, combined with bioinformatics, revealed a pathogenic 5'UTR GCH1 substitution. The +142C>T single nucleotide 5'UTR substitution that segregates with affected status in DRD patients, substantially attenuates translation without altering RNA expression levels or stability. The +142C>T substitution disrupts translation most likely by creating an upstream initiation start codon (uAUG) and an upstream open reading frame (uORF).
CONCLUSIONS/SIGNIFICANCE: This is the first GCH1 regulatory substitution reported to act at a post-transcriptional level, increasing the list of genetic diseases caused by abnormal translation and reaffirming the importance of investigating potential regulatory substitutions in genetic diseases.
GCH1 基因突变与儿童发病、多巴反应性肌张力障碍（DRD）有关。鉴于用左旋多巴治疗后有完全康复的可能，正确诊断 DRD 至关重要。大多数与 DRD 相关的突变位于 GCH1 基因的编码区，但在 mRNA 的 5'非翻译区（5'UTR）内也报告了另外三个单核苷酸序列取代。这些 5'UTR GCH1 序列取代的生物学意义尚未进行分析。
方法/主要发现：荧光素酶报告基因检测、实时定量 PCR 和 RNA 衰减测定，结合生物信息学，揭示了一种致病性的 5'UTR GCH1 取代。与 DRD 患者受累状态共分离的+142C>T 单核苷酸 5'UTR 取代，在不改变 RNA 表达水平或稳定性的情况下，显著减弱翻译。+142C>T 取代很可能通过创建一个上游起始密码子（uAUG）和一个上游开放阅读框（uORF）来破坏翻译。
结论/意义：这是第一个被报道在转录后水平起作用的 GCH1 调节取代，增加了由异常翻译引起的遗传疾病的列表，并再次证实了在遗传疾病中研究潜在调节取代的重要性。
