A novel cryptic exon identified in the 3′ region of intron 2 of the human dystrophin gene
A novel cryptic exon identified in the 3′ region of intron 2 of the human dystrophin gene
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DOI：
10.1007/s10038-005-0272-6
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发表时间：
2005-09-01
影响因子：
3.5
通讯作者：
Matsuo, M
中科院分区：
文献类型：
--
作者：
Tran, VK;Zhang, ZJ;Matsuo, M
在杜氏肌营养不良症（DMD）中突变的肌营养不良蛋白基因是已知的最大的人类基因，其特征在于其内含子的巨大尺寸。内含子2是第二大内含子，长170-kb，并已被证明在其5'区包括一个140-bp的隐蔽外显子（外显子2a）。这个内含子的其余部分没有已知的功能。在这项研究中，我们发现另一个隐藏的外显子，位于内含子2的3'区，被激活的启动子或组织特异性的方式。一个未知的98 bp插入精确的外显子2和3之间被确定在一个肌营养不良蛋白的mRNA从淋巴细胞的DMD患者与外显子2的重复。这段98 bp的序列位于内含子2的3'端，具有一个分支点、受体和供体剪接位点共有序列以及一个外显子剪接增强子序列，因此是一个新的外显子，我们将其命名为“外显子2b”。“在淋巴细胞中，在肌肉特异性启动子驱动的转录物中检测到外显子2b掺入。20个正常人组织的mRNA，包括心脏和骨骼肌的mRNA，被证实含有一个片段，从外显子1延伸到外显子2b的逆转录PCR扩增，表明外显子2b被激活的组织特异性的方式。这为肌营养不良症的新病因提供了线索。
The dystrophin gene, which is mutated in Duchenne muscular dystrophy (DMD), is the largest known human gene and is characterized by the huge size of its introns. Intron 2, the second largest intron, is 170-kb long and has been shown to include a 140-bp cryptic exon (exon 2a) in its 5' region. The rest of this intron has no known function. In this study, we find that another cryptic exon, located in the 3' region of intron 2, is activated in a promoter- or tissue-specific manner. An unknown 98-bp insertion precisely between exons 2 and 3 was identified in one of the dystrophin mRNAs from lymphocytes of a DMD patient with a duplication of exon 2. This 98-bp sequence, located in the 3' region of intron 2, was found to possess a branch point, acceptor and donor splice-site consensus sequences, and an exonic splicing enhancer sequence, and thus is a novel exon, which we named "exon 2b." In lymphocytes, exon 2b incorporation was detected in the muscle-specific, promoter-driven transcript. Five of 20 normal human tissue mRNAs, including cardiac and skeletal muscle mRNAs, were confirmed to contain a fragment extending from exon 1 to exon 2b by reverse transcription PCR amplification, indicating that exon 2b is activated in a tissue-specific manner. This provides a clue to a novel cause of dystrophinopathy.