Three of 12 transgenic mice derived from oocyte injection were found to produce F1 progeny expressing high levels of chloramphenicol acetyltransferase (CAT) in the heart. Line 34, estimated to carry 4 copies of the transgene, was selected for propagation and experimental use because it was the most fertile.

PCR analysis of tissues of mice generated from fertilized oocytes in which Cre recombinase was transiently expressed demonstrated efficient excision of the chloramphenicol acetyltransferase gene. Beta-galactosidase activity is very high in muscle and heart of these mice, but not above background elsewhere.