BAC RP23-112F24 was used to obtain the entire Tph2 coding sequence; the following was inserted in-frame immediately after the Tph2 start codon: an eArchT3.0 cDNA sequence (described further below), a viral 2A oligopeptide sequence, an enhanced green fluorescent protein (EGFP), a woodchuck hepatitis virus posttranscriptional regulatory element (WPRE; to enhance mRNA stability) and a bovine growth hormone polyadenylation signal (BGHpA) The eArchT3.0 sequence is a mammalian codon-optimized cDNA encoding ArchT (the Archaerhodopsin-3 protein [aop3] derived from the halophilic bacterium Halorubrum strain TP009) that was further modified to have a neurite/membrane-trafficking signal (TS) sequence (amino acids GEYIPLDQIDINV) and an endoplasmic reticulum (ER) exporting sequence (amino acids FCYENEV). (J:341572)