Dual regulation of cryptochrome 1 mRNA expression in... : NeuroReport (original) (raw)

Rhythms

Dual regulation of cryptochrome 1 mRNA expression in chicken retina by light and circadian oscillators

Haque, Rashidul; Chaurasia, Shyam S.; Wessel, James H. III; Iuvone, P. MichaelCA

Department of Pharmacology, Emory University School of Medicine, 1510 Clifton Rd NE, Atlanta, GA 30322, USA

CACorresponding Author: [email protected]

Received 9 September 2002; accepted 30 September 2002

Abstract

The localization and regulation of chicken cryptochrome 1 (cCry1) mRNA expression in retina was investigated by laser capture microdissection and quantitative real-time RT-PCR. Laser capture microdissection (LCM) of retinal cell layers showed the highest level of cCry1 expression in the ganglion cell and photoreceptor layers. In both layers, expression was high during the daytime and low at night in subjects exposed to a 12:12 h light:dark cycle. Robust circadian oscillations of cCry1 mRNA levels were observed in constant (24 h day) light, but not in constant darkness, with the highest expression during daytime at zeitgeber time (ZT) 8. Unlike cCry1, circadian rhythms of the melatonin-synthesizing enzyme, arylalkylamine _N_-acetyltransferase, persisted in constant darkness, suggesting that rhythmic cCry1 expression is not essential for circadian clock function or output. On the second day of constant darkness, when cCry1 expression is arrhythmic, light exposure for 2 h significantly increased retinal cCry1 mRNA levels at ZT 4 and 8, times that cCry1 expression is induced in LD and LL. Similar light exposure ending at ZT 20 had no significant effect. Thus, expression of cCry1 mRNA is regulated dually by light and circadian clocks.