Myc^tm39Mnz

A targeting vector containing a self-excising loxP-flanked neomycin/sperm-specific Cre cassette was used to delete the promoter, first non-coding exon and a portion of intron 1 of the Mycn gene. This 2.2 Kb deletion removed promoters PO, P1, and P2 while leaving promoter P3 intact. The construct was electroporated into CY2.4 albino C57BL/6J-Tyrc-2J-derived embryonic stem (ES) cells. Correctly targeted ES clones were injected into recipient blastocysts. The resulting male chimeric animals were crossed to C57BL/6J-Tyrc-2J mice to allow for coat-color screening of germline transmission and for self-excision of the neomycin/Cre cassette. RNA-FISH analysis of heterozygote B cells indicated RNA transcription occcured only at one allele compared to the biallelic transcription observed in wild-type B cells. (J:145691)