Williams Adam, Harker Nicola, Ktistaki Eleni, Veiga-Fernandes Henrique, Roderick Kathleen, Tolaini Mauro, Norton Trisha, Williams Keith, Kioussis Dimitris
Division of Molecular Immunology, The National Institute for Medical Research, London, NW71AA, UK.
Nucleic Acids Res. 2008 Apr;36(7):2320-9. doi: 10.1093/nar/gkn085. Epub 2008 Feb 22.
Sequences proximal to transgene integration sites are able to deregulate transgene expression resulting in complex position effect phenotypes. In addition, transgenes integrated as repeated arrays are susceptible to repeat-induced gene silencing. Using a Cre recombinase-based system we have addressed the influence of transgene copy number (CN) on expression of hCD2 transgenes. CN reduction resulted in a decrease, increase or no effect on variegation depending upon the site of integration. This finding argues that repeat-induced gene silencing is not the principle cause of hCD2 transgene variegation. These results also suggest that having more transgene copies can be beneficial at some integration sites. The transgenic lines examined in this report also exhibited a form of imprinting, which was manifested by decreased levels of expression and increased levels of variegation, upon maternal transmission; and this correlated with DNA hypermethylation and a reduction in epigenetic chromatin modifications normally associated with active genes.
转基因整合位点附近的序列能够使转基因表达失调，从而导致复杂的位置效应表型。此外，以重复阵列形式整合的转基因易受重复诱导的基因沉默影响。我们使用基于Cre重组酶的系统研究了转基因拷贝数（CN）对hCD2转基因表达的影响。根据整合位点的不同，CN的减少对斑驳现象可产生降低、增加或无影响。这一发现表明，重复诱导的基因沉默不是hCD2转基因斑驳现象的主要原因。这些结果还表明，在某些整合位点拥有更多的转基因拷贝可能是有益的。本报告中检测的转基因品系还表现出一种印记形式，在母系遗传时表现为表达水平降低和斑驳程度增加；这与DNA高甲基化以及通常与活性基因相关的表观遗传染色质修饰减少有关。
