Generation and validation of a D1 dopamine receptor Flpo knock-in mouse

Background: Dopamine is a powerful neuromodulator of diverse brain functions, including movement, motivation, reward, and cognition. D1-type dopamine receptors (D1DRs) are the most prevalently expressed dopamine receptors in the brain. Neurons expressing D1DRs are heterogeneous and involve several subpopulations. Although these neurons can be studied with BAC-transgenic rodents, these models have some limitations especially when considering their integration with conditional or intersectional genetic tools. New Method: We developed a novel Drd1-P2A-Flpo (Drd1-Flpo) mouse line in which the Flpo gene was knocked in immediately after the Drd1 gene using CRISPR-Cas9. We validated the Drd1-Flpo line by confirming Flp expression and functionality specific to D1DR+ neurons with immunohistochemistry and in situ hybridization. Comparison with Existing Methods: The Drd1-Flpo line is a useful resource for studying subpopulations of D1DR+ neurons with intersectional genetic tools. Conclusions: We demonstrated brain-wide GFP expression driven by Drd1-Flpo, suggesting that this mouse line may be useful for comprehensive anatomical and functional studies in many brain regions. The Drd1-Flpo model will advance the study of dopaminergic signaling by providing a new tool for investigating the diverse roles of D1DR+ neurons and their subpopulations in brain disease.