Guo Xiaoyan, Lin Mingrui, Shi Tengfei, Yan Wei, Chen Wenxu
Department of Laboratory Medicine, The Second Hospital of Fuzhou Affiliated to Xiamen University.
Intensive Care Unit, The Affiliated People's Hospital of Fujian Traditional Medical University.
Tohoku J Exp Med. 2017 Jul;242(3):173-181. doi: 10.1620/tjem.242.173.
Multiple osteochondromas (MO) is one of the most common benign bone tumors in humans with an autosomal dominant hereditary mode. MO is a genetic heterogeneity disease with variable number and size of osteochondromas, as well as changeable number and location of diseased bones. Mutations in Exostosin-1/Exostosin-2 (EXT1/EXT2) genes are the main molecular basis of MO. EXT1 and EXT2 genes encode exostosin 1 and exostosin 2, respectively, both of which are transmembrane glycosyltransferases that elongate the chains of heparin sulfate (HS) at HS proteoglycans (HSPGs). HSPGs are considered to be involved in regulating the proliferation and differentiation of chondrocytes. Owing to large size of EXT1/EXT2 genes and lack of mutation hotspots, molecular diagnosis of MO is challenging. Here, we applied targeted next-generation sequencing (t-NGS) in mutation screening of EXT1/EXT2 genes for 10 MO patients. The results were compared and validated with Sanger sequencing. Overall, nine mutations identified by t-NGS were confirmed with Sanger sequencing, excluding two variants of false positive, suggesting the reliability of mutation screening by t-NGS. The nine mutations identified by t-NGS include two missense mutations (EXT1: c.1088G>A and c.2120C>T), one splicing mutation (EXT2: c.744-1G>T), and six nonsense mutations (EXT1: c.351C>G, c.1121G>A, and c.1843_1846dup; EXT2: c.67C>T, c.561delG, and c.575T>A). In summary, our paper provides the primary data of the application of t-NGS in MO molecular diagnosis, including six newly identified mutations (EXT1: c.1843_1846dup, c.1088G>A, c.351C>G, and c.2120C>T and EXT2: c.744-1G>T and c.575T>A), which further enrich the mutation database of MO from the Chinese population.
多发性骨软骨瘤（MO）是人类最常见的良性骨肿瘤之一，呈常染色体显性遗传模式。MO是一种具有遗传异质性的疾病，骨软骨瘤的数量和大小各不相同，患病骨骼的数量和位置也会发生变化。外生骨疣蛋白-1/外生骨疣蛋白-2（EXT1/EXT2）基因的突变是MO的主要分子基础。EXT1和EXT2基因分别编码外生骨疣蛋白1和外生骨疣蛋白2，二者均为跨膜糖基转移酶，可延长硫酸乙酰肝素（HS）蛋白聚糖（HSPG）上硫酸乙酰肝素（HS）的链。HSPG被认为参与调节软骨细胞的增殖和分化。由于EXT1/EXT2基因较大且缺乏突变热点，MO的分子诊断具有挑战性。在此，我们应用靶向二代测序（t-NGS）对10例MO患者的EXT1/EXT2基因进行突变筛查。将结果与桑格测序进行比较和验证。总体而言，t-NGS鉴定出的9个突变经桑格测序得到确认，排除了2个假阳性变异，表明t-NGS进行突变筛查的可靠性。t-NGS鉴定出的9个突变包括2个错义突变（EXT1：c.1088G>A和c.2120C>T）、1个剪接突变（EXT2：c.744-1G>T）和6个无义突变（EXT1：c.351C>G、c.1121G>A和c.1843_1846dup；EXT2：c.67C>T、c.561delG和c.575T>A）。总之，我们的论文提供了t-NGS在MO分子诊断中应用的原始数据，包括6个新鉴定的突变（EXT1：c.1843_1846dup、c.1088G>A、c.351C>G和c.2120C>T以及EXT2：c.744-1G>T和c.575T>A），这进一步丰富了中国人群MO的突变数据库。
