Based on studies in mouse, NPAS4 binds the promoter of the CDK5 gene in differentiating neurons (Yun et al. 2013). The promoter region of the mouse Cdk5 gene that Npas4 binds to is conserved in the human CDK5 gene promoter. It is uncertain whether NPAS4 heterodimerized with ARNT, ARNT2 or ARNTL binds to the CDK5 gene promoter. Therefore, all three complexes (NPAS4:ARNT, NPAS4:ARNT2 and NPAS4:ARNTL) are shown as candidates. Binding of Arnt and Arnt2 to the promoter of Cdk5 gene in primary cultures of rat neurons was detected but binding of Npas4 to the Cdk5 gene promoter was not reported (Brigidi et al. 2019).