CRE-MEDIATED SOMATIC SITE-SPECIFIC RECOMBINATION IN MICE

Conditional mutant mice equipped with heterologous recombination syste ms (Cre/lox or Flp/frt) are promising for studying tissue-specific gen e function and for designing better models of human diseases. The util ity of these mice depends on the cell target specificity, on the effic iency and on the control over timing of gene (in)activation, We have e xplored the utility of adenoviral vectors and transgenic mice expressi ng Cre under the control of tissue-specific promoters to achieve Cre/ lex-mediated somatic recombination of the LacZ reporter gene, using a newly generated flex LacZ mouse strain. When adeno Cre viruses were ad ministered via different routes, recombination and expression of LacZ was detected in a wide range of tissues, Whereas in liver beta-galacto sidase activity was quickly lost by turnover of expressing cells, even though the recombined allele was retained, beta-galactosidase in othe r tissues persisted for many months. Our data indicate that the flex L acZ transgenic line can be utilized effectively to monitor the level a nd functionality of Cre protein produced upon infection with adeno Cre virus or upon crossbreeding with different Cre transgenic lines.