The HSA-driven CreERt2 transgene was inserted in cis with a cassette containing a constitutively active form of Atk1 fused to EGFP (c.a.Akt-EGFP). Prior to the addition of tamoxifen, the HSA promoter drives transctiption of CreERt2, with absence of c.a.Akt-EGFP transcription. Upon the addition of tamoxifen, CreERt2 expression would drive its own excision, leaving the c.a.Akt-EGFP cassette downstream of the HSA promoter.