A tubulin promoter drives expression of a transcription unit that encodes two open reading frames (ORFs) separated by a T2A motif (to allow separate translation of each ORF). The first ORF encodes the miRFP680 fluorescent protein, tagged at the N-terminal end with 3xTag:HA. The second ORF encodes a heme oxygenase 1 (HO1) gene that is required for miRFP680 to fluoresce.