The FRT cassette in fzAct.FRT.mKate,sfGFP has been excised, allowing expression of the fz coding region (tagged with sfGFP and mKate) from an Actin promoter. The fz-sfGFP-mKate fusion protein can be used as a "fluorescent timer" to study fz turnover, due to the different maturation rates of the two fluorophores.