The construct consists of ~18 kbp of the human neurofilament heavy polypeptide promoter (NEFH; from BAC RP11-91J21) upstream of the tetracycline-regulated transactivator gene (tTA or "Tet-Off"), followed by a polyA signal. Founder line 8 has its highest tTA expression in developmental late stage of the cortex, cerebellum and hippocampus, with expression also observed in olfactory bulb and in the rest of the brain.