Circadian Rhythms in Cultured Mammalian Retina

TLDR

Retinal functions are circadian, yet the clock location is largely unknown. Cultured hamster retinas produce circadian melatonin rhythms for at least five days at 27 °C, entrain to light cycles, run free in darkness, and tau mutants shorten the period, demonstrating a genetically programmed retinal oscillator controlling melatonin synthesis.

Abstract

Many retinal functions are circadian, but in most instances the location of the clock that drives the rhythm is not known. Cultured neural retinas of the golden hamster ( Mesocricetus auratus ) exhibited circadian rhythms of melatonin synthesis for at least 5 days at 27°C. The rhythms were entrained by light cycles applied in vitro and were free-running in constant darkness. Retinas from hamsters homozygous for the circadian mutation tau , which shortens the free-running period of the circadian activity rhythm by 4 hours, showed a shortened free-running period of melatonin synthesis. The mammalian retina contains a genetically programmed circadian oscillator that regulates its synthesis of melatonin.