We previously showed that the genotype-phenotype correlation in MPS II is well-conserved in Japan (Kosuga et al., 2016). Almost all of our patients with attenuated MPS II have missense variants, which is expected to result in residual activity of iduronate-2-sulfatase. In contrast, our patients with severe MPS II have so-called null-type disease-associated variants, such as nonsense variants, frame-shifts, gene insertions, gene deletions and rearrangement with pseudogene (IDS2), none of which are expected to result in residual activity. However, we recently encountered a patient with attenuated MPS II who had a presumable null-type disease-associated variant and 76-base deletion located in exon 1 that extended into intron 1. To investigate this discordance, we extracted RNA from the leukocytes of the patient and performed reverse transcription polymerase chain reaction. One of the bands of the cDNA analysis was found to include a nucleotide sequence whose transcript was expected to generate an almost full-length IDS mature peptide lacking only part of its signal peptide as well as only one amino acid at the end of the N-terminus. This suggests that an alternative splicing donor site is generated in exon 1 upstream of the deleted region. Based on these observations, we concluded that the phenotype-genotype discordance in this patient with MPS II was due to the decreased amount of IDS protein induced by the low level of the alternatively spliced mRNA, lacking part of the region coding for the signal peptide but including the region coding almost the full mature IDS protein. The first 25 amino acids at the N-terminus of IDS protein are a signal peptide. The alternative splice transcript has only 13 (1 M-13 L) of those 25 amino acids; 14G-25G are missing, suggesting that the exclusively hydrophobic 1 M-13 L of the signal peptide of IDS might have a crucial role in the signal peptide.

我们之前已经证明MPS II中的基因型与表型相关性在日本保存良好（Kosuga et al。，2016）。我们几乎所有的MPS II减毒患者都有错义变异体，预计会导致异氰酸酯2-硫酸酯酶的残留活性。相反，我们患有严重MPS II的患者具有所谓的空型疾病相关变体，例如无意义变体，移码，基因插入，基因缺失和假基因重排（IDS2），预计不会导致任何残留活动。但是，我们最近遇到了一位患有MPS II减毒的患者，该患者在外显子1中具有一个推测的与无效型疾病相关的变异，并具有76个碱基的缺失，并延伸到内含子1中。为了研究这种矛盾，我们从该白细胞的白细胞中提取了RNA。患者并进行了逆转录聚合酶链反应。发现cDNA分析的一条带包含一个核苷酸序列，其转录本有望产生几乎全长的IDS成熟肽，该肽仅缺少其信号肽的一部分，而在N-末端仅缺少一个氨基酸。总站。这表明在缺失区域上游的外显子1中产生了一个可变的剪接供体位点。基于这些观察，我们得出的结论是，该MPS II患者的表型-基因型不一致是由于交替剪接的mRNA水平低引起的IDS蛋白量减少，缺乏编码信号肽的部分区域，但几乎包括了编码区域完整的成熟IDS蛋白。IDS蛋白N端的前25个氨基酸是信号肽。备选剪接转录本在这25个氨基酸中只有13个（1 M-13 L）；缺少14G-25G，这表明IDS信号肽的仅疏水1 M-13 L可能在信号肽中起关键作用。缺少编码信号肽的区域的一部分，但包括编码几乎完整的成熟IDS蛋白的区域。IDS蛋白N端的前25个氨基酸是信号肽。备选剪接转录本在这25个氨基酸中只有13个（1 M-13 L）；缺少14G-25G，这表明IDS信号肽的仅疏水1 M-13 L可能在信号肽中起关键作用。缺少编码信号肽的区域的一部分，但包括编码几乎完整的成熟IDS蛋白的区域。IDS蛋白N端的前25个氨基酸是信号肽。备选剪接转录本在这25个氨基酸中只有13个（1 M-13 L）；缺少14G-25G，这表明IDS信号肽的仅疏水1 M-13 L可能在信号肽中起关键作用。