Murine α-Lactalbumin Gene Inactivation and Replacment
We are using gene targeting to investigate the role of α-lactalbumin in lactation and the regulation of α-lactalbumin gene expression. Gene targeting in embryonic stem (ES) cells is now widely used to inactivate genes of interest. We have recently demonstrated a powerful technique, termed double replacement, whereby a wide variety of genetic alterations can be engineered at a chosen locus and the effects examined in mice (Stacey et al.,1994) The procedure involves two consecutive rounds of gene targeting: the first creates a null allele of the gene of interest, which can then be replaced with DNA carrying experimental alterations in the second round. This process effects a clean replacement of DNA sequences, and no unwanted exogenous DNA (eg marker genes) are left at the target site. A most useful aspect of double replacement gene targeting is that multiple independent second step targeting experiments can be carried out, making it possible to produce and compare many experimental alterations at the same locus.