Role of BMAL1 and CLOCK in regulating the secretion of melatonin in chick retina under monochromatic green light.

As the circadian pacemaker of birds, the retina possesses the ability to receive light information, generate circadian oscillation, and secrete melatonin. Previous studies have confirmed that monochromatic green light can accelerate the circadian rhythmic expression of clock genes in the chick retina, thereby increasing mRNA level and melatonin secretion. However, as the core components of the transcriptional-translational negative feedback loop, the role that and plays in the regulation of the retinal molecular clock system and melatonin secretion under monochromatic green light is unknown. To explore their in these processes, embryonic chick retinal cells at six embryo ages were isolated and cultured under light-dark (LD) 12:12 monochromatic green light with, and the role of and in the regulation of the retinal molecular clock and melatonin secretion in the chick retina was explored by siRNA interference and overexpression. The results showed siRNA interference and overexpression of obliterated the circadian rhythm of , and melatonin secretion. Moreover, the siRNA interference of significantly reduced the average expression levels of the positive clock genes and , positive clock protein CLOCK, negative clock genes , as well as and retinal melatonin. The over-expression of increased the average levels of the above-detected targets. However, siRNA interference and overexpression of did not change the rhythm of all of the clock genes, clock proteins, , and melatonin secretion, while it only affected the circadian mesors (24 h time series means), amplitudes, and acrophases (peak times) of , and melatonin, as well as the average levels of arrhythmic and . Moreover, interference and overexpression of did not affect mRNA level and BMAL1 protein expression. The above results reveal interference and overexpression of completely abolished the molecular circadian oscillation and the rhythm of melatonin output signal of chick retinal cells, indicating that is on the top of the avian retinal molecular clock feedback loop and regulates the downstream molecular clock oscillation and output under monochromatic green light. plays a subordinate role in maintaining the circadian oscillation of the molecular clock and melatonin secretion in retinal cells, and it has a stabilizing and amplifying effect on molecular clock oscillation.