Targeting genes for self-excision in the germ line

A procedure is described that directs the self-induced deletion of DNA sequ ences as they pass through the male germ line of mice. The testes-specific promoter from the angiotensin-converting enzyme gene was used to drive expr ession of the Cre-recombinase gene. Cre was linked to the selectable marker Neo(x), and the two genes flanked with 1oxP elements. This cassette was ta rgeted to the Hoxa3 gene in mouse ES cells that were in turn used to genera te chimeric mice. In these chimeras, somatic cells derived from the ES cell s retained the cassette, but self-excision occurred in all ES-cell-derived sperm.