An ~538 kb region, containing Myc enhancers Rr357, Rr21 and Rr356 and the 5' end of CTCF-binding region Rr303293, was deleted by cre-mediated inter-allelic recombination between the loxP sites in alleles Rr357tm1.1Jta and Rr303293tm1.1Jta. (J:257088)