Epigenetic Silencing of Nuclear Transgenes in Chlamydomonas

最近在这个实验室已经证明，表观遗传转录失活发生在藻类和高等植物中。在衣藻中，两种机制，即染色质/核结构域和DNA甲基化，被假设为负责机制。为了验证这些工作假设，本项目有以下具体目标：1)分离转录基因沉默缺陷的标记突变体，2)克隆和表征参与转录抑制的标记基因，以及3)绘制沉默和稳定的转基因位点的染色体位置。转基因植物和动物的生产正迅速成为常规，但引入的基因往往表达不稳定，导致新获得的性状丧失或减少表现。这种转基因沉默现象通常是由多种表观遗传机制引起的，这些机制在转录和转录后水平上都起作用。在大多数情况下，潜在的分子过程还没有被精确地识别出来。这项工作的结果可能有助于更好地理解真核生物的表观遗传现象，因为初步数据表明分子机制可能是进化保守的。衣藻表观遗传基因沉默的分析可以为了解控制基因表达的染色体/细胞核组织的基本特征提供遗传学途径。从实践的角度来看，这些结果可能有助于开发克服表观遗传沉默方法的方法，从而有助于转基因植物和动物的产生。

Cerutti 9808473It has recently been demonstrated in this laboratory that epigenetic transcriptional inactivation occurs in algae as well as in higher plants. In Chlamydomonas, two mechanisms, namely chromatin/nuclear domains and DNA methylation, are hypothesized to be the responsible mechanisms. In order to test these working hypotheses, this project has the following specific aims: 1) To isolate tagged mutants defective in transcription gene silencing, 2) To clone and characterize a tagged gene(s) involved in transcription repression, and 3) To map the chromosomal location of silenced and stable transgenic loci.The production of transgenic plants and animals is rapidly becoming routine, but the introduced genes are often unstably expressed, leading to the loss or reduced manifestation of newly acquired traits. This phenomenon of transgene silencing often results from a variety of epigenetic mechanisms, operating at both transcriptional and post-transcriptional levels. In most cases the underlying molecular processes have not been precisely identified. The results of this work could contribute to a greater understanding of epigenetic phenomena in eukaryotes, since preliminary data suggest that the molecular mechanisms might be evolutionarily conserved. The analysis of epigenetic gene silencing in Chlamydomonas can provide a genetic approach for understanding essential features of chromosomal/nuclear organization controlling gene expression. From a practical perspective, the results could contribute to the development of methods to overcome epigenetic silencing methodology, which could contribute to the generation of transgenic plants and animals.