Fig. 3

Odor input-dependent spine formation mediated by the transcription factor neuronal Per/Arnt/Sim domain protein 4 (Npas4) in the olfactory bulb (OB) interneurons. a Neural stem cells that will differentiate into OB interneurons are generated throughout life in the subventricular zone and migrate along the rostral migratory stream into the OB. After the stem cells arrive at the OB, they differentiate into interneurons and are incorporated into the pre-existing neural circuit. During incorporation, dendritic arbors and spines are formed. b In wild-type OB, odor inputs can induce Npas4 expression, which suppresses the Mdm2 expression. The suppression of Mdm2 promotes the spine formation of OB interneurons mediated by doublecortin (Dcx). Alternatively in Npas4-knockout OB, loss of Npas4 expression upregulates the expression of Mdm2, which ubiquitinates Dcx, leading to the degradation of Dcx and a reduction in the dendritic spine density of OB interneurons