Nr4a2, A Key Factor Controlling the Development and Functional Maintenance of Forebrain Car3 Neurons.

Nr4a2 (Nurr1) is well known to be vital for midbrain dopaminergic neurons. Recent single-cell RNA analyses reveal that Nr4a2 is expressed in lateral cerebral regions, within neurons named L4/L5/L6 IT Car3. These neurons have attracted intense attention for the molecular mechanisms underlying their development and functions. We classified Car3 neurons into neocortical (Ncx-Car3), claustral (CLA-Car3), and dorsal endopiriform nucleus (dEn-Car3) subpopulations, focusing on the characterization of Ncx-Car3 neurons. These neurons exhibit distinct birthdates and migratory morphologies compared to CLA- and dEn-Car3 neurons, but share a common transcriptomic profile when Nr4a2 is deleted at the embryonic stage or in adulthood. Notably, Nr4a2 misexpression ectopically induces Car3-enriched genes in vivo. Mice lacking Nr4a2 in Car3 ensembles during the embryonic stage or in adulthood display hyperactivity and reduced anxiety-like behaviors. Therefore, our results demonstrate that Nr4a2 is a key factor in regulating the development and functional maintenance of the forebrain Car3 neurons.