EGFR and Migration of Neural Progenitors

Protein phosphorylation keeps circadian clocks wound, triggering rhythmic transcriptional events throughout the day. This week, Lin et al. identify phosphorylation sites on the Drosophila circadian protein PERIOD (PER). Mutations in casein kinase 2 (CK2) result in abnormal circadian phenotypes and altered PER nuclear localization, and CK2 specifically phosphorylates PER in vitro. The authors focused on three CK2 consensus sites on the N-terminal segment of PER, consisting of S/T-X-X-D/E amino acid sequences, two of which appeared to be responsible for CK2 phosphorylation in vitro. They then made alanine mutations of each site and looked at their effect on circadian function. Single, double, and triple mutations caused period lengthening. In perS149-151-153A triple mutants, PER localized to the nuclei of a ventral group of lateral pacemaker neurons 2 h later than in wild-type flies. The authors propose that nuclear entry of PER is triggered by CK2 phosphorylation and contributes to period regulation. ΠDevelopment/Plasticity/Repair EGFR and Migration of Neural Progenitors