The microinjected embryos are transferred into oviducts of pseudopregnant foster mothers that subsequently produce the transgene carrying founders at varying frequencies. Because the transgene randomly integrates as one or more copies into the mouse genome prior to embryo cleavage, all cells including those of extraembryonic origin will eventually carry the transgene ( 3, 4). The second method that has been the widely used procedure since its discovery almost 25 years ago, involves the direct microinjectioin of foreign DNA into the pronuclei of fertilized one-cell mouse embryos. Because of many technical problems, this method is not in practice for routine production of transgenic mice ( 2). The first method involves DNA delivery by retroviral infection of mouse embryos at different developing stages.
In the following sections, we will discuss general principles of transgenic mouse technology and provide detailed methods in later sections.įoreign DNA can be introduced into the mouse genome mainly by three ways. Our group has generated several lines of transgenic mice that phenocopy many human reproductive diseases. Moreover, micromanipulation of one-cell mouse embryos is considered technically relatively easy when compared to that in other species. Mice are routinely used for this purpose, because they are relatively inexpensive, easy to maintain and breed and a large amount of data are available with regard to chromosomal mapping and linkage analysis of many mouse genes ( 2). This technology often known as the transgenic animal technology has become the most popular method of introducing foreign DNA into a host genome. Several advances in gene cloning, chromosomal mapping and DNA sequencing and a wealth of breeding data on various species have heralded a new era of introducing foreign DNA into chromosomes of the host species ( 2). Although initially started as a means to improve and select for the good qualities of species, the potential of gene manipulation was not realized until random mutagenesis screens were devised in bacteriophages and fruit flies in order to score the resultant phenotypes ( 1). Gene manipulation has been the constant pursuit of geneticists since the end of the 19th century.
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