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Does The Precision Of A Biological Clock Depend Upon Its Period? Effects Of The Duper And Tau Mutations In Syrian Hamsters, Eric L. Bittman
Does The Precision Of A Biological Clock Depend Upon Its Period? Effects Of The Duper And Tau Mutations In Syrian Hamsters, Eric L. Bittman
Eric L. Bittman
Mutations which alter the feedback loops that generate circadian rhythms may provide insight into their insensitivity to perturbation robustness) and their consistency of period (precision). I examined relationships between endogenous period, activity and rest (τDD, α and ρ) in Syrian hamsters using two different mutations, duper and tau, both of which speed up the circadian clock. I generated 8 strains of hamsters that are homozygous or heterozygous for the tau, duper, and wild type alleles in all combinations. The endogenous period of activity onsets among these strains ranged from 17.94+0.04 to 24.13±0.04 h. Contrary to predictions, the variability of period …
Duper: A Mutation That Shortens Hamster Circadian Period, Eric L. Bittman, S Monecke, J Brewer Mckinley, S Krug
Duper: A Mutation That Shortens Hamster Circadian Period, Eric L. Bittman, S Monecke, J Brewer Mckinley, S Krug
Eric L. Bittman
Three animals born to homozygous tau mutant (τss, “super short”) Syrian hamsters showed extremely short free-running periods of locomotor activity (τDD of approximately 17.8 hours). Inbreeding produced 33 such “super duper” animals, which had a τDD of 18.09 ± 0.05 hours, which was shorter than that of τss hamsters (20.66 ± 0.07 hours, p < 0.001). To test the hypothesis that a gene (Duper) is responsible for a 2-hour shortening of τDD, we backcrossed super duper hamsters to unrelated τss animals. The F1 pups uniformly had a τDD similar to that of τss hamsters (19.89 ± 0.15 hours), but F2 animals showed a 1:1 ratio of the 18- to 20-hour phenotypes. In contrast, the F1 of a cross between super duper hamsters and τss animals presumed heterozygous for duper showed a 1:1 ratio of 18- to 20-hour phenotypes, and inbreeding of the super duper F1 offspring uniformly produced F2 pups with extremely short τDD (17.86 ± 0.5 hours). We isolated the duper mutation on a wild-type background through crossing of super duper with wild-type animals. Restriction digests identified short-period F2 pups that lack the mutant CK1ε allele, and these animals had a mean τDD of 23.11 ± 0.04 hours. τDD of duper hamsters born and raised in DD was significantly shorter than in hamsters raised in 14L:10D (21.92 ± 0.12 hours, p < 0.0001). τDD shortened twice as much in τs and τss hamsters than in wild-type animals that were homozygous for duper, indicating the presence of epistatic interactions. Assortment of phenotypes in the F2 generation fit the expected distribution for expression of duper as recessive (χ2 = 6.41, p > 0.1). Neither CK1ε nor CK1δ coding region base sequences differed between super duper and τss hamsters. The growth rate of super duper mutants is similar to that of τss animals but slightly but significantly reduced at particular postweaning time points. We conclude that duper represents a …
Effects Of The Duper Mutation On Circadian Responses To Light, Eric L. Bittman, S. Krug, J. M. Brewer, A. S. Bois
Effects Of The Duper Mutation On Circadian Responses To Light, Eric L. Bittman, S. Krug, J. M. Brewer, A. S. Bois
Eric L. Bittman
The circadian mutation duper in Syrian hamsters shortens the free-running circadian period (τDD) by 2 hours when expressed on a tau mutant (τss) background and by 1 hour on a wild-type background. We have examined the effects of this mutation on phase response curves and entrainment. In contrast to wild types, duper hamsters entrained to 14L:10D with a positive phase angle. Super duper hamsters (expressing duper on a τss background) showed weak entrainment, while τss animals either completely failed to entrain or showed sporadic entrainment with episodes of relative coordination. As previously reported, wild-type and τss hamsters show low amplitude …
Circadian Organization Oftau Mutant Hamsters: Aftereffects And Splitting, Eric L. Bittman, M. K. Costello, J. M. Brewer
Circadian Organization Oftau Mutant Hamsters: Aftereffects And Splitting, Eric L. Bittman, M. K. Costello, J. M. Brewer
Eric L. Bittman
Homozygous tau mutant (τss) hamsters show an extremely short (20 h) circadian period (τ) that is attributable to altered enzymatic activity of casein kinase 1ε. It has been proposed that coupling of constituent circadian oscillators is strengthened in τss hamsters, explaining their tendency to show strong resetting after prolonged exposure to constant darkness. To evaluate further the circadian organization of τss hamsters, the authors assessed the extent of shortening of period as an aftereffect of exposure to light:dark cycles whose period (T) is 91% of τ and the ability of constant light to induce splitting. They find that τss hamsters …
Regulation Of Prokineticin 2 Expression By Light And The Circadian Clock, Michelle Y. Cheng, Eric L. Bittman, Samer Hattar, Qun Yong Zhou
Regulation Of Prokineticin 2 Expression By Light And The Circadian Clock, Michelle Y. Cheng, Eric L. Bittman, Samer Hattar, Qun Yong Zhou
Eric L. Bittman
Background: The suprachiasmatic nucleus (SCN) contains the master circadian clock that regulates daily rhythms of many physiological and behavioural processes in mammals. Previously we have shown that prokineticin 2 (PK2) is a clock-controlled gene that may function as a critical SCN output molecule responsible for circadian locomotor rhythms. As light is the principal zeitgeber that entrains the circadian oscillator, and PK2 expression is responsive to nocturnal light pulses, we further investigated the effects of light on the molecular rhythm of PK2 in the SCN. In particular, we examined how PK2 responds to shifts of light/dark cycles and changes in photoperiod. …
Expression Of Haper1 And Habmal1 In Syrian Hamsters: Heterogeneity Of Transcripts And Oscillations In The Periphery, Eric L. Bittman, Yanhong Tong, Hongnian Guo, Judy Mckinley Brewer, Alexamder S. Bois
Expression Of Haper1 And Habmal1 In Syrian Hamsters: Heterogeneity Of Transcripts And Oscillations In The Periphery, Eric L. Bittman, Yanhong Tong, Hongnian Guo, Judy Mckinley Brewer, Alexamder S. Bois
Eric L. Bittman
The molecular biology of circadian rhythms has been extensively studied in mice, and the widespread expression of canonical circadian clock genes in peripheral organs is well established in this species. In contrast, much less information about the peripheral expression of haPer1, haPer2, and haBmal1 is available in Syrian hamsters despite the fact that this species is widely used for studies of circadian organization and photoperiodic responses. Furthermore, examination of oscillating expression of these genes in mouse testis has generated discrepant results, and little is known about gonadal expression of haPer1 and haBmal1 or their environmental control. To address these questions, …