新技术“剪贴”基因治疗遗传病

美国研究人员6月26日在英国《自然》杂志上报告说，他们在实验鼠体内实现了通过“剪切”和“粘贴”基因来治疗血友病。这一技术有望用于治疗其他遗传病。

英国《自然》杂志网站刊登报告说，美国费城儿童医院等机构的研究人员用这种方法有效治疗了患有血友病的实验鼠。血友病是由基因变异引起的一种遗传病，患者血液中缺少凝血物质，往往有个小伤口就会流血不止，通常只能采取注射凝血物质的方法来进行治疗。本次研究中的实验鼠患有乙型血友病，是由基因变异导致肝脏细胞不能产生一种凝血物质引起。

研究人员用病毒作为载体，将一种名为“锌指核酸酶”的物质送入活体实验鼠的肝脏细胞中。锌指核酸酶是基因学中所用的“剪刀”，可用于剪断DNA（脱氧核糖核酸）链条，研究人员用它精确地剪除了细胞DNA中基因序列上发生变异的部分。随后，再用病毒作为载体，将一段正确的基因序列送入细胞中，细胞在修复DNA链条的同时也就“粘贴”好了正确的基因序列。

结果显示，用这种方法治疗的实验鼠，体内相应凝血物质的量可恢复到正常数量的5%左右，其血液也能较快自行凝结。领导研究的凯瑟琳·海伊说，在相应凝血物质的量恢复到5%的情况下，血友病症状已大大减轻，如果不是动手术等情况，一般不会出现严重的出血不止现象。

此前研究人员只对试管中的细胞“剪贴”过基因，这是首次成功在活体动物体内进行类似操作。经过8个月的观察，实验鼠肝脏未出现异常。研究人员因此认为，本次成果原则上证明了基因“剪贴”疗法的有效性，将来也许可用于治疗多种遗传疾病。

推荐原文出处：

Nature     doi:10.1038/nature10177

In vivo genome editing restores haemostasis in a mouse model of haemophilia

Hojun Li; Virginia Haurigot; Yannick Doyon; Tianjian Li; Sunnie Y. Wong; Anand S. Bhagwat; Nirav Malani; Xavier M. Anguela; Rajiv Sharma; Lacramiora Ivanciu; Samuel L. Murphy; Jonathan D. Finn; Fayaz R. Khazi; Shangzhen Zhou; David E. Paschon; Edward J. Rebar; Frederic D. Bushman; Philip D. Gregory; Michael C. Holmes; Katherine A. High

Editing of the human genome to correct disease-causing mutations is a promising approach for the treatment of genetic disorders. Genome editing improves on simple gene-replacement strategies by effecting in situ correction of a mutant gene, thus restoring normal gene function under the control of endogenous regulatory elements and reducing risks associated with random insertion into the genome. Gene-specific targeting has historically been limited to mouse embryonic stem cells. The development of zinc finger nucleases (ZFNs) has permitted efficient genome editing in transformed and primary cells that were previously thought to be intractable to such genetic manipulation1. In vitro, ZFNs have been shown to promote efficient genome editing via homology-directed repair by inducing a site-specific double-strand break (DSB) at a target locus2, 3, 4, but it is unclear whether ZFNs can induce DSBs and stimulate genome editing at a clinically meaningful level in vivo. Here we show that ZFNs are able to induce DSBs efficiently when delivered directly to mouse liver and that, when co-delivered with an appropriately designed gene-targeting vector, they can stimulate gene replacement through both homology-directed and homology-independent targeted gene insertion at the ZFN-specified locus. The level of gene targeting achieved was sufficient to correct the prolonged clotting times in a mouse model of haemophilia B, and remained persistent after induced liver regeneration. Thus, ZFN-driven gene correction can be achieved in vivo, raising the possibility of genome editing as a viable strategy for the treatment of genetic disease.