十四、问题与展望
大量研究已证实转基因小鼠是特异性研究骨发生发育的极为稳定而有效的工具。或许因为骨是出现在进化过程晚期的组织之一，小鼠和人的骨骼系统中大部分基因具有相似的功能。Cre-lox系统使得人们可以在某一时刻特异性敲除某种基因，从而解码基因功能及骨对其他组织的影响。然而，尽管转基因技术近年来得到了很大的发展，但依然存在着一些问题。如Cre重组酶转基因的表达模式、靶基因重组效率的差异、Cre重组酶的毒性、遗传背景、育种策略、实验对照、基因冗余等诸多方面，越来越引起人们的强烈关注［20］。例如，Cre转基因小鼠的卵子或精子中的RNA或者蛋白质可以遗传给非转基因的后代而引起非靶向的基因敲除。这种现象在雌小鼠中更为常见［73-75］。用3.6kb或2.3kb Collαl-Cre小鼠敲除Igf1，Cream教授和她的研究小组发现部分Cre阴性小鼠后代也发生了基因的重组敲除［46］。3.6kb Collαl-Cre或2.3kb Collαl-Cre为母本的后代重组率分别高达50%和28%［46］。因此，Collαl-Cre转基因应通过父本遗传，没有遗传Cre基因的后代小鼠仍需进行基因型检测来确认是否存在基因重组。这些发现同时引起了对于如何选择对照小鼠的思考。当研究中运用到条件性基因敲除小鼠， “野生型”对照小鼠可以是不携带Cre转基因的floxed小鼠，或是Cre转基因阳性的小鼠。前者可用于研究插入Lox序列可能引起的所有干扰，而后者则用于研究Cre重组酶的活性对于基因组的可能影响。相信随着转基因技术在理论和技术上的不断完善，这些面临的问题会逐渐得到解决，转基因动物在骨软骨生物学研究中的应用必将更加深入和普遍。
（屠锦雯 周 虹）
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