Pleiotropic effects of cryptochromes 1 and 2 on free-running and light-entrained murine circadian rhythms.
Cryptochromes function in both light entrainment of circadian rhythms and in a peripheral circadian clock mechanism in Drosophila. Mice have two closely related cryptochrome genes (mCry1 and mCry2). To further understand the roles of mammalian cryptochromes, we bred mice to carry all possible combinations of wild-type and cryptochrome knockout alleles, and tested these mice for free-running and entrained circadian rhythmicity. We find that a single wild-type copy of mCry1, but not mCry2, is sufficient for free running circadian rhythmicity; however, these mice show markedly variable free-running periods. Two wild-type copies of either mCry1 or mCry2 are sufficient to establish a stable free-running clock. A subset of mCry1-/mCry-; mCry2-/mCry2- mice have a diurnal activity preference, suggesting that cryptochromes function in light-dependent behavioral masking. We also analyzed mice lacking both cryptochromes and carrying the homozygous rd retinal degeneration mutation. These mice have markedly depressed behavioral photoresponses in light-dark conditions, despite having an anatomically intact retinohypothalamic tract and normal expression of melanopsin. These results suggest that, similar to insect cryptochromes, mammalian cryptochromes function pleiotropically in both circadian rhythm generation and in photic entrainment and behavioral responses.
Van Gelder
Russell N
RN
Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA. vangelder@vision.wustl.edu
Gibler
Therese M
TM
Tu
Daniel
D
Embry
Kris
K
Selby
Christopher P
CP
Thompson
Carol L
CL
Sancar
Aziz
A
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D002940:Circadian Rhythm / Q000235:genetics*; D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D009154:Mutation; D010775:Photic Stimulation; D017956:Photoreceptor Cells, Invertebrate; D043562:Receptors, G-Protein-Coupled; D012162:Retinal Degeneration / Q000235:genetics
D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins; D043562:Receptors, G-Protein-Coupled; C119828:cry protein, Drosophila