Gene targeting is a powerful tool for the studies of in vivo gene functions. However, the null mutants produced by currently available targeting techniques are frequently accompanied by either developmental deficit from subtle to embryonic death or non-phenotypes since the deficits associated with the missing gene are functionally or genetically compensated. All these concerns have dramatically complicated the interpretation of the results or even misled the conclusion in terms of gene functions. Therefore, to develop a novel technique that is able to solve these concerns is of most importance in the studies of in vivo gene functions, especially for behavioral genomics. Based on the principles that both trans-acting and cis-acting are the essential mechanisms for gene transcription in eukaryotic cells, we have development a novel transposon system that is able to tag any gene of interest and produce inducible/reversible mRNA knockout in the mouse. The novelty of Dr. Tang's system is to change the strategy of deletion of a crucial part of a targeted gene, which is the principle for traditional knockout techniques including conventional or the currently available conditional gene knockout techniques, such as Cre/loxP recombination system, to the strategy of inactivation of (inducible knockout) or reactivation of (reversible to normal) mRNA transcription. The most striking promise of this system is to allow one to temporally associate mRNA transcription with a given biological or behavioral process. Therefore, it will be particularly useful for the studies of gene function in relation to complicated biological and behavioral processes. There are 20,000-25,000 genes in the mouse genome. With 30% genes expressed in the brain, at least 7,500 genes are necessary to tag and further study for a comprehensive understanding of behavioral genomics. Based on the feasibility of this novel system and the progress in the mouse genome project, it is reasonable to establish a small library for gene targeted transposon tagged ES cell lines. At the first stage, the PI will produce presenilin-1 (PS-1) and BDNF transposon tagged ES cell lines and then the knockout mice to validate this system and later on, 20-60 ES lines are expected to be established. Due to the fact that to maintain colonies of mutant mouse lines requires extensive husbandry space as well as labor, it will be eventually required to establish a large or complete tagged ES cell library in our whole research community. Thus, the development of this novel technology will significantly contribute to other efforts on the functional (behavioral) genomics in this post-genome era.
