Postnatal ontogenesis of moleular clock genes in mouse striatum

Abstract

Objective To study the mRNA expression profiles of clock genes in mouse striatum during postnatal ontogenesis. Methods C57 BL/6J male mice were grouped with development stages:early postnatal stage (postnatal day 3),pre-weaning stage (postnatal day 14) and adult (postnatal day 60). Animals were transferred into constant darkness for 24 hours and sacrificed at 6 h intervals beginning at 09:00 h local time (01 HALO=Hours after Light Onset). The striatum were dissected out. 24h mRNA oscillations of 5 principle clock genes (Bmal1,Clock,Cry1,Per1 and Rev-erbα) were examined using real time PCR. Results At P3,no daily oscillation was found for all clock genes. At P14,a significant time effect was identified only for Rev-erb α (P=0.027),with peak value at 19 to 01 HALO. At P60,the daily oscillations of these clock genes were at least borderline significant (Bmal1:P=0.004,Clock:P=0.004,Per1:P=0.004,Rev-erbα:P=0.004),with peak time at 01 HALO for Bmal1,Clock and Cry1; at 13 HALO for Per1; and at 07 HALO for Rev-erbα. In addition,the overall mean mRNA levels of these clock genes also underwent a dynamic change postnatally. For Bmal1,Clock,Per1 and Rev-erbα,the expression level increased throughout the postnatal ontogenesis from P3,P14 to P60. For Cry1,however,the abundance at P3 and P60 were similar while that at P14 was much lower. Conclusion The striatal molecular clock machinery,although works efficiently in adult,develops gradually after birth in mice. Key words: Circadian; Expression; Postnatal; Striatum