Massironi S M G, Reis B L F S, Carneiro J G, Barbosa L B S, Ariza C B, Santos G C, Guénet J L, Godard A L B
Departamento de Imunologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP, Brasil.
Braz J Med Biol Res. 2006 Sep;39(9):1217-26. doi: 10.1590/s0100-879x2006000900009.
When compared to other model organisms whose genome is sequenced, the number of mutations identified in the mouse appears extremely reduced and this situation seriously hampers our understanding of mammalian gene function(s). Another important consequence of this shortage is that a majority of human genetic diseases still await an animal model. To improve the situation, two strategies are currently used: the first makes use of embryonic stem cells, in which one can induce knockout mutations almost at will; the second consists of a genome-wide random chemical mutagenesis, followed by screening for mutant phenotypes and subsequent identification of the genetic alteration(s). Several projects are now in progress making use of one or the other of these strategies. Here, we report an original effort where we mutagenized BALB/c males, with the mutagen ethylnitrosourea. Offspring of these males were screened for dominant mutations and a three-generation breeding protocol was set to recover recessive mutations. Eleven mutations were identified (one dominant and ten recessives). Three of these mutations are new alleles (Otop1mlh, Foxn1sepe and probably rodador) at loci where mutations have already been reported, while 4 are new and original alleles (carc, eqlb, frqz, and Sacc). This result indicates that the mouse genome, as expected, is far from being saturated with mutations. More mutations would certainly be discovered using more sophisticated phenotyping protocols. Seven of the 11 new mutant alleles induced in our experiment have been localized on the genetic map as a first step towards positional cloning.
与其他基因组已测序的模式生物相比，在小鼠中鉴定出的突变数量似乎极少，这种情况严重阻碍了我们对哺乳动物基因功能的理解。这种短缺的另一个重要后果是，大多数人类遗传疾病仍等待动物模型。为改善这种情况，目前采用了两种策略：第一种利用胚胎干细胞，在其中几乎可以随意诱导基因敲除突变；第二种是全基因组随机化学诱变，随后筛选突变表型并鉴定遗传改变。现在有几个项目正在利用这两种策略中的一种或另一种开展。在此，我们报告一项原创性工作，我们用诱变剂乙基亚硝基脲处理BALB/c雄性小鼠。对这些雄性小鼠的后代进行显性突变筛选，并制定了三代繁殖方案以恢复隐性突变。鉴定出了11个突变（1个显性突变和10个隐性突变）。其中3个突变是在已报道有突变的位点上的新等位基因（Otop1mlh、Foxn1sepe，可能还有rodador），而4个是新的原始等位基因（carc、eqlb、frqz和Sacc）。这一结果表明，正如预期的那样，小鼠基因组远未被突变饱和。使用更复杂的表型分析方案肯定会发现更多突变。在我们的实验中诱导产生的11个新突变等位基因中的7个已定位到遗传图谱上，这是进行定位克隆的第一步。
