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Manoogian ENC, Bahiru MS, Wang EJ, Holder M, Bittman EL. Neuroendocrine effects of the duper mutation in Syrian hamsters: a role for Cryptochrome 1. Front Physiol 2024; 15:1351682. [PMID: 38444761 PMCID: PMC10912188 DOI: 10.3389/fphys.2024.1351682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 01/31/2024] [Indexed: 03/07/2024] Open
Abstract
Molecular and physiological determinants of the timing of reproductive events, including the pre-ovulatory LH surge and seasonal fluctuations in fertility, are incompletely understood. We used the Cryptochrome 1-deficient duper mutant to examine the role of this core circadian clock gene in Syrian hamsters. We find that the phase of the LH surge and its stability upon shifts of the light: dark cycle are altered in duper mutants. The intensity of immunoreactive PER1 in GnRH cells of the preoptic area peaks earlier in the day in duper than wild type hamsters. We note that GnRH fibers coursing through the suprachiasmatic nucleus (SCN) contact vasopressin- and VIP-immunoreactive cells, suggesting a possible locus of circadian control of the LH surge. Unlike wild types, duper hamsters do not regress their gonads within 8 weeks of constant darkness, despite evidence of melatonin secretion during the subjective night. In light of the finding that the duper allele is a stop codon in Cryptochrome 1, our results suggest important neuroendocrine functions of this core circadian clock gene.
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Affiliation(s)
| | | | | | | | - Eric L. Bittman
- Department of Biology and Program in Neuroscience, University of Massachusetts, Amherst, MA, United States
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2
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Bahiru MS, Bittman EL. Adult Neurogenesis Is Altered by Circadian Phase Shifts and the Duper Mutation in Female Syrian Hamsters. eNeuro 2023; 10:ENEURO.0359-22.2023. [PMID: 36878716 PMCID: PMC10062491 DOI: 10.1523/eneuro.0359-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 02/10/2023] [Accepted: 02/16/2023] [Indexed: 03/08/2023] Open
Abstract
Cell birth and survival in the adult hippocampus are regulated by a circadian clock. Rotating shift work and jet lag disrupt circadian rhythms and aggravate disease. Internal misalignment, a state in which abnormal phase relationships prevail between and within organs, is proposed to account for adverse effects of circadian disruption. This hypothesis has been difficult to test because phase shifts of the entraining cycle inevitably lead to transient desynchrony. Thus, it remains possible that phase shifts, regardless of internal desynchrony, account for adverse effects of circadian disruption and alter neurogenesis and cell fate. To address this question, we examined cell birth and differentiation in the duper Syrian hamster (Mesocricetus auratus), a Cry1-null mutant in which re-entrainment of locomotor rhythms is greatly accelerated. Adult females were subjected to alternating 8 h advances and delays at eight 16 d intervals. BrdU, a cell birth marker, was given midway through the experiment. Repeated phase shifts decreased the number of newborn non-neuronal cells in WT, but not in duper hamsters. The duper mutation increased the number of BrdU-IR cells that stained for NeuN, which marks neuronal differentiation. Immunocytochemical staining for proliferating cell nuclear antigen indicated no overall effect of genotype or repeated shifts on cell division rates after 131 days. Cell differentiation, assessed by doublecortin, was higher in duper hamsters but was not significantly altered by repeated phase shifts. Our results support the internal misalignment hypothesis and indicate that Cry1 regulates cell differentiation. Phase shifts may determine neuronal stem cell survival and time course of differentiation after cell birth. Figure created with BioRender.
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Affiliation(s)
- Michael Seifu Bahiru
- Program in Neuroscience and Behavior, University of Massachusetts, Amherst, Massachusetts 01003
| | - Eric L Bittman
- Program in Neuroscience and Behavior, University of Massachusetts, Amherst, Massachusetts 01003
- Department of Biology, University of Massachusetts, Amherst, Massachusetts 01003
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3
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The duper mutation reveals previously unsuspected functions of Cryptochrome 1 in circadian entrainment and heart disease. Proc Natl Acad Sci U S A 2022; 119:e2121883119. [PMID: 35930669 PMCID: PMC9371649 DOI: 10.1073/pnas.2121883119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The Cryptochrome 1 (Cry1)-deficient duper mutant hamster has a short free-running period in constant darkness (τDD) and shows large phase shifts in response to brief light pulses. We tested whether this measure of the lability of the circadian phase is a general characteristic of Cry1-null animals and whether it indicates resistance to jet lag. Upon advance of the light:dark (LD) cycle, both duper hamsters and Cry1-/- mice re-entrained locomotor rhythms three times as fast as wild types. However, accelerated re-entrainment was dissociated from the amplified phase-response curve (PRC): unlike duper hamsters, Cry1-/- mice show no amplification of the phase response to 15' light pulses. Neither the amplified acute shifts nor the increased rate of re-entrainment in duper mutants is due to acceleration of the circadian clock: when mutants drank heavy water to lengthen the period, these aspects of the phenotype persisted. In light of the health consequences of circadian misalignment, we examined effects of duper and phase shifts on a hamster model of heart disease previously shown to be aggravated by repeated phase shifts. The mutation shortened the lifespan of cardiomyopathic hamsters relative to wild types, but this effect was eliminated when mutants experienced 8-h phase shifts every second week, to which they rapidly re-entrained. Our results reveal previously unsuspected roles of Cry1 in phase shifting and longevity in the face of heart disease. The duper mutant offers new opportunities to understand the basis of circadian disruption and jet lag.
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4
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Vijaya Shankara J, Horsley KG, Cheng N, Rho JM, Antle MC. Circadian Responses to Light in the BTBR Mouse. J Biol Rhythms 2022; 37:498-515. [PMID: 35722987 PMCID: PMC9452857 DOI: 10.1177/07487304221102279] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Animals with altered freerunning periods are valuable in understanding properties of the circadian clock. Understanding the relationship between endogenous clock properties, entrainment, and influence of light in terms of parametric and non-parametric models can help us better understand how different populations adapt to external light cycles. Many clinical populations often show significant changes in circadian properties that in turn cause sleep and circadian problems, possibly exacerbating their underlying clinical condition. BTBR T+Itpr3tf/J (BTBR) mice are a model commonly used for the study of autism spectrum disorders (ASD). Adults and adolescents with ASD frequently exhibit profound sleep and circadian disruptions, including increased latency to sleep, insomnia, advanced and delayed sleep phase disorders, and sleep fragmentation. Here, we investigated the circadian phenotype of BTBR mice in freerunning and light-entrained conditions and found that this strain of mice showed noticeably short freerunning periods (~22.75 h). In addition, when compared to C57BL/6J controls, BTBR mice also showed higher levels of activity even though this activity was compressed into a shorter active phase. Phase delays and phase advances to light were significantly larger in BTBR mice. Despite the short freerunning period, BTBR mice exhibited normal entrainment in light-dark cycles and accelerated entrainment to both advanced and delayed light cycles. Their ability to entrain to skeleton photoperiods of 1 min suggests that this entrainment cannot be attributed to masking. Period differences were also correlated with differences in the number of vasoactive intestinal polypeptide–expressing cells in the suprachiasmatic nucleus (SCN). Overall, the BTBR model, with their unique freerunning and entrainment properties, makes an interesting model to understand the underlying circadian clock.
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Affiliation(s)
- Jhenkruthi Vijaya Shankara
- Department of Psychology, University of Calgary, Calgary, AB, Canada.,Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Katelyn G Horsley
- Department of Psychology, University of Calgary, Calgary, AB, Canada.,Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Ning Cheng
- Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.,Department of Comparative Biology & Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
| | - Jong M Rho
- Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.,Departments of Neurosciences and Pediatrics, University of California, San Diego and Rady Children's Hospital, San Diego, California, USA
| | - Michael C Antle
- Department of Psychology, University of Calgary, Calgary, AB, Canada.,Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.,Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
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5
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Lee YY, Cal-Kayitmazbatir S, Francey LJ, Bahiru MS, Hayer KE, Wu G, Zeller MJ, Roberts R, Speers J, Koshalek J, Berres ME, Bittman EL, Hogenesch JB. duper is a null mutation of Cryptochrome 1 in Syrian hamsters. Proc Natl Acad Sci U S A 2022; 119:e2123560119. [PMID: 35471909 PMCID: PMC9170138 DOI: 10.1073/pnas.2123560119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 03/08/2022] [Indexed: 12/20/2022] Open
Abstract
The duper mutation is a recessive mutation that shortens the period length of the circadian rhythm in Syrian hamsters. These animals show a large phase shift when responding to light pulses. Limited genetic resources for the Syrian hamster (Mesocricetus auratus) presented a major obstacle to cloning duper. This caused the duper mutation to remain unknown for over a decade. In this study, we did a de novo genome assembly of Syrian hamsters with long-read sequencing data from two different platforms, Pacific Biosciences and Oxford Nanopore Technologies. Using two distinct ecotypes and a fast homozygosity mapping strategy, we identified duper as an early nonsense allele of Cryptochrome 1 (Cry1) leading to a short, unstable protein. CRY1 is known as a highly conserved component of the repressive limb of the core circadian clock. The genome assembly and other genomic datasets generated in this study will facilitate the use of the Syrian hamster in biomedical research.
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Affiliation(s)
- Yin Yeng Lee
- Divisions of Human Genetics and Immunobiology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH 45229
| | - Sibel Cal-Kayitmazbatir
- Divisions of Human Genetics and Immunobiology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
| | - Lauren J. Francey
- Divisions of Human Genetics and Immunobiology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
| | - Michael Seifu Bahiru
- Department of Biology, University of Massachusetts Amherst, Amherst, MA 01003
- Program in Neuroscience & Behavior, University of Massachusetts Amherst, Amherst, MA 01003
| | - Katharina E. Hayer
- Institute for Translational Medicine and Therapeutics, University of Pennsylvania, Philadelphia, PA 19104
| | - Gang Wu
- Divisions of Human Genetics and Immunobiology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
| | - Molly J. Zeller
- University of Wisconsin Biotechnology Center, University of Wisconsin–Madison, Madison, WI 53706
| | - Robyn Roberts
- University of Wisconsin Biotechnology Center, University of Wisconsin–Madison, Madison, WI 53706
| | - James Speers
- University of Wisconsin Biotechnology Center, University of Wisconsin–Madison, Madison, WI 53706
| | - Justin Koshalek
- University of Wisconsin Biotechnology Center, University of Wisconsin–Madison, Madison, WI 53706
| | - Mark E. Berres
- University of Wisconsin Biotechnology Center, University of Wisconsin–Madison, Madison, WI 53706
| | - Eric L. Bittman
- Department of Biology, University of Massachusetts Amherst, Amherst, MA 01003
- Program in Neuroscience & Behavior, University of Massachusetts Amherst, Amherst, MA 01003
| | - John B. Hogenesch
- Divisions of Human Genetics and Immunobiology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
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Manoogian ENC, Kumar A, Obed D, Bergan J, Bittman EL. Suprachiasmatic function in a circadian period mutant: Duper alters light-induced activation of vasoactive intestinal peptide cells and PERIOD1 immunostaining. Eur J Neurosci 2019; 48:3319-3334. [PMID: 30346078 DOI: 10.1111/ejn.14214] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 09/07/2018] [Accepted: 09/18/2018] [Indexed: 11/28/2022]
Abstract
Mammalian circadian rhythms are entrained by photic stimuli that are relayed by retinal projections to the core of the suprachiasmatic nucleus (SCN). Neuronal activation, as demonstrated by expression of the immediate early gene c-fos, leads to transcription of the core clock gene per1. The duper mutation in hamsters shortens circadian period and amplifies light-induced phase shifts. We performed two experiments to compare the number of c-FOS immunoreactive (ir) and PER1-ir cells, and the intensity of staining, in the SCN of wild-type (WT) and duper hamsters at various intervals after presentation of a 15-min light pulse in the early subjective night. Light-induced c-FOS-ir within 1 hr in the dorsocaudal SCN of duper, but not WT hamsters. In cells that express vasoactive intestinal peptide (VIP), which plays a critical role in synchronization of SCN cellular oscillators, light-induced c-FOS-ir was greater in duper than WT hamsters. After the light pulse, PER1-ir cells were found in more medial portions of the SCN than FOS-ir, and appeared with a longer latency and over a longer time course, in VIP cells of duper than wild-type hamsters. Our results indicate that the duper allele alters SCN function in ways that may contribute to changes in free running period and phase resetting.
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Affiliation(s)
- Emily N C Manoogian
- Program in Neuroscience and Behavior, University of Massachusetts, Amherst, Massachusetts
| | - Ajay Kumar
- Program in Neuroscience and Behavior, University of Massachusetts, Amherst, Massachusetts
| | - Doha Obed
- Department of Biology, University of Massachusetts, Amherst, Massachusetts
| | - Joseph Bergan
- Psychological and Brain Sciences and Program in Neuroscience and Behavior, University of Massachusetts, Amherst, Massachusetts
| | - Eric L Bittman
- Department of Biology, Program in Neuroscience and Behavior, University of Massachusetts, Amherst, Massachusetts
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7
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Surov A, Banaszek A, Bogomolov P, Feoktistova N, Monecke S. Dramatic global decrease in the range and reproduction rate of the European hamster Cricetus cricetus. ENDANGER SPECIES RES 2016. [DOI: 10.3354/esr00749] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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8
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Early doors (Edo) mutant mouse reveals the importance of period 2 (PER2) PAS domain structure for circadian pacemaking. Proc Natl Acad Sci U S A 2016; 113:2756-61. [PMID: 26903623 DOI: 10.1073/pnas.1517549113] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The suprachiasmatic nucleus (SCN) defines 24 h of time via a transcriptional/posttranslational feedback loop in which transactivation of Per (period) and Cry (cryptochrome) genes by BMAL1-CLOCK complexes is suppressed by PER-CRY complexes. The molecular/structural basis of how circadian protein complexes function is poorly understood. We describe a novel N-ethyl-N-nitrosourea (ENU)-induced mutation, early doors (Edo), in the PER-ARNT-SIM (PAS) domain dimerization region of period 2 (PER2) (I324N) that accelerates the circadian clock of Per2(Edo/Edo) mice by 1.5 h. Structural and biophysical analyses revealed that Edo alters the packing of the highly conserved interdomain linker of the PER2 PAS core such that, although PER2(Edo) complexes with clock proteins, its vulnerability to degradation mediated by casein kinase 1ε (CSNK1E) is increased. The functional relevance of this mutation is revealed by the ultrashort (<19 h) but robust circadian rhythms in Per2(Edo/Edo); Csnk1e(Tau/Tau) mice and the SCN. These periods are unprecedented in mice. Thus, Per2(Edo) reveals a direct causal link between the molecular structure of the PER2 PAS core and the pace of SCN circadian timekeeping.
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9
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Manoogian ENC, Leise TL, Bittman EL. Phase resetting in duper hamsters: specificity to photic zeitgebers and circadian phase. J Biol Rhythms 2015; 30:129-43. [PMID: 25633984 DOI: 10.1177/0748730414568297] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The duper mutation in Syrian hamsters shortens the free-running period of locomotor activity (τDD) to about 23 h and results in a type 0 phase-response curve (PRC) to 15-min light pulses. To determine whether exaggerated phase shifts are specific to photic cues and/or restricted to subjective night, we subjected hamsters to novel wheel confinements and dark pulses during subjective day. Small phase shifts elicited by the nonphotic cue were comparable in mutant and wild-type (WT) hamsters, but dark pulses triggered larger shifts in dupers. To assess further the effects of the duper mutation on light-dark transitions, we transferred hamsters between constant light (LL) and constant dark (DD) or between DD and LL at various circadian phases. Duper hamsters displayed significantly larger phase shifts than WT hamsters when transferred from LL to DD during subjective day and from DD to LL during subjective night. The variability of phase shifts in response to all light/dark transitions was significantly greater in duper hamsters at all time points. In addition, most duper hamsters, but none of the WTs, displayed transient ultradian wheel-running patterns for 5 to 12 days when transferred from light to dark at CT 18. The χ(2) periodogram and autocorrelation analyses indicate that these ultradian patterns differ from the disruption of rhythmicity by SCN lesions or exposure to constant bright light. We conclude that the duper mutation specifically amplifies phase shifts to photic cues and may destabilize coupling of circadian organization upon photic challenge due to weakened coupling among components of the circadian pacemaker. Mathematical modeling of the circadian pacemaker supports this hypothesis.
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Affiliation(s)
- Emily N C Manoogian
- Department of Biology and Program in Neuroscience and Behavior, University of Massachusetts, Amherst, Massachusetts
| | - Tanya L Leise
- Department of Mathematics & Statistics, Amherst College, Amherst, Massachusetts
| | - Eric L Bittman
- Department of Biology and Program in Neuroscience and Behavior, University of Massachusetts, Amherst, Massachusetts
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10
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Tchitchek N, Safronetz D, Rasmussen AL, Martens C, Virtaneva K, Porcella SF, Feldmann H, Ebihara H, Katze MG. Sequencing, annotation and analysis of the Syrian hamster (Mesocricetus auratus) transcriptome. PLoS One 2014; 9:e112617. [PMID: 25398096 PMCID: PMC4232415 DOI: 10.1371/journal.pone.0112617] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2014] [Accepted: 10/06/2014] [Indexed: 11/18/2022] Open
Abstract
Background The Syrian hamster (golden hamster, Mesocricetus auratus) is gaining importance as a new experimental animal model for multiple pathogens, including emerging zoonotic diseases such as Ebola. Nevertheless there are currently no publicly available transcriptome reference sequences or genome for this species. Results A cDNA library derived from mRNA and snRNA isolated and pooled from the brains, lungs, spleens, kidneys, livers, and hearts of three adult female Syrian hamsters was sequenced. Sequence reads were assembled into 62,482 contigs and 111,796 reads remained unassembled (singletons). This combined contig/singleton dataset, designated as the Syrian hamster transcriptome, represents a total of 60,117,204 nucleotides. Our Mesocricetus auratus Syrian hamster transcriptome mapped to 11,648 mouse transcripts representing 9,562 distinct genes, and mapped to a similar number of transcripts and genes in the rat. We identified 214 quasi-complete transcripts based on mouse annotations. Canonical pathways involved in a broad spectrum of fundamental biological processes were significantly represented in the library. The Syrian hamster transcriptome was aligned to the current release of the Chinese hamster ovary (CHO) cell transcriptome and genome to improve the genomic annotation of this species. Finally, our Syrian hamster transcriptome was aligned against 14 other rodents, primate and laurasiatheria species to gain insights about the genetic relatedness and placement of this species. Conclusions This Syrian hamster transcriptome dataset significantly improves our knowledge of the Syrian hamster's transcriptome, especially towards its future use in infectious disease research. Moreover, this library is an important resource for the wider scientific community to help improve genome annotation of the Syrian hamster and other closely related species. Furthermore, these data provide the basis for development of expression microarrays that can be used in functional genomics studies.
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Affiliation(s)
- Nicolas Tchitchek
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America
| | - David Safronetz
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, Montana, United States of America
| | - Angela L Rasmussen
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America
| | - Craig Martens
- Genomics Unit, Research Technologies Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, Montana, United States of America
| | - Kimmo Virtaneva
- Genomics Unit, Research Technologies Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, Montana, United States of America
| | - Stephen F Porcella
- Genomics Unit, Research Technologies Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, Montana, United States of America
| | - Heinz Feldmann
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, Montana, United States of America
| | - Hideki Ebihara
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, Montana, United States of America
| | - Michael G Katze
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America; Washington National Primate Research Center, University of Washington, Seattle, Washington, United States of America
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11
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Bittman EL. Effects of the duper mutation on responses to light: parametric and nonparametric responses, range of entrainment, and masking. J Biol Rhythms 2014; 29:97-109. [PMID: 24682204 DOI: 10.1177/0748730413520399] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The duper mutation in Syrian hamsters shortens the free-running period (τDD) of locomotor activity by approximately 1 h when expressed on the wild-type background and by 2 h on the tau mutant background ("super duper"). In either case, duper markedly amplifies the phase response curve (PRC) of the light pulse. This work examined whether the duper mutation alters parametric as well as nonparametric properties, intensity thresholds, and noncircadian responses to light. Furthermore, it assessed the effects of duper on the range of entrainment and circadian aftereffects. In the first study, duper mutant and wild-type (wt) hamsters showed a similar intensity threshold for light-induced phase shifts. In the second, wt, tau mutant, and super duper hamsters were exposed to LD cycles whose period (T) progressively shortened. Regardless of whether the light phase was held at 50% of T or fixed at 3 h, super duper mutants entrained to a wider range of T cycles and showed aftereffects upon release into DD. In the third study, τLL was measured in mutant and wt hamsters that were maintained for 30-day intervals in constant light of progressively greater intensities. With increasing light intensity, the circadian period shortened in duper mutants. Circadian rhythms of super duper hamsters were disrupted at light intensities considerably below those that induced arrhythmicity in wt, tau heterozygote, or duper homozygote hamsters. In the fourth study, hamsters that were wt or homozygous for duper received two 15-min light pulses: the first at CT14 to CT16 or CT17 to CT19 and the second 2 h later. As expected, wt and duper mutants showed weak and strong resetting, respectively. Light pulses in early subjective night had an additive effect in mutant but not in wt hamsters, indicating that larger phase shifts of the pacemaker take longer to complete. Finally, super duper hamsters showed slightly but not significantly more negative masking than did wt or duper mutant hamsters. These results indicate that the duper mutation affects the properties of the central circadian pacemaker. The mutant allele affects not only the PRC but also parametric responses to light.
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Affiliation(s)
- Eric L Bittman
- Department of Biology and Program in Neuroscience and Behavior, University of Massachusetts, Amherst, MA, USA
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12
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Bittman EL. Does the precision of a biological clock depend upon its period? Effects of the duper and tau mutations in Syrian hamsters. PLoS One 2012; 7:e36119. [PMID: 22615753 PMCID: PMC3352912 DOI: 10.1371/journal.pone.0036119] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Accepted: 03/29/2012] [Indexed: 02/07/2023] Open
Abstract
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 was unrelated to its absolute value: all strains showed similar variability of τDD when activity onsets and acrophase were used as phase markers. The τDD of activity offsets was more variable than onsets but also differed little between genotypes. Cycle variation and precision were not correlated with τDD within any strain, and only weakly correlated when all strains are considered together. Only in animals homozygous for both mutations (super duper hamsters) were cycle variation and precision reduced. Rhythm amplitude differed between strains and was positively correlated with τDD and precision. All genotypes showed negative correlations between α and ρ. This confirms the expectation that deviations in the duration of subjective day and night should offset one another in order to conserve circadian period, even though homeostatic maintenance of energy reserves predicts that longer intervals of activity or rest would be followed by longer durations of rest or activity. Females consistently showed greater variability of the period of activity onset and acrophase, and of α, but variability of the period of offset differed between sexes only in super duper hamsters. Despite the differences between genotypes in τDD, ρ was consistently more strongly correlated with the preceding than the succeeding α.
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Affiliation(s)
- Eric L Bittman
- Department of Biology, University of Massachusetts, Amherst, Massachusetts, United States of America.
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13
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Krug S, McKinley Brewer J, Bois AS, Bittman EL. Effects of the duper mutation on circadian responses to light. J Biol Rhythms 2011; 26:293-304. [PMID: 21775288 DOI: 10.1177/0748730411411570] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2023]
Abstract
The circadian mutation duper in Syrian hamsters shortens the free-running circadian period (τ(DD)) by 2 hours when expressed on a tau mutant (τ(ss)) 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 τ(ss) background) showed weak entrainment, while τ(ss) animals either completely failed to entrain or showed sporadic entrainment with episodes of relative coordination. As previously reported, wild-type and τ(ss) hamsters show low amplitude resetting in response to 15-minute light pulses after short-term (10 days) exposure to DD. In contrast, super duper hamsters show high amplitude resetting. This effect is attributable to the duper allele, as hamsters carrying duper on a wild-type background also show large phase shifts. Duper mutants that were born and raised in DD also showed high amplitude resetting in response to 15-minute light pulses, indicating that the effect of the mutation on PRC amplitude is not an aftereffect of entrainment to 14L:10D. Hamsters that are heterozygous for duper do not show amplified resetting curves, indicating that for this property, as for determination of free-running period, the mutant allele is recessive. In a modified Aschoff type II protocol, super duper and duper hamsters show large phase shifts as soon as the second day of DD. Despite the amplification of the PRC in super duper hamsters, the induction of Period1 gene expression in the SCN by light is no greater in these mutants than in wild-type animals. Period2 expression in the SCN did not differ between super duper and wild-type hamsters exposed to light at CT15, but albumin site D-binding protein (Dbp) mRNA showed higher basal levels and greater light induction in the SCN of super duper compared to wild-type animals. These results indicate that the duper mutation alters the amplitude of the circadian oscillator and further distinguish it from the tau mutation.
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Affiliation(s)
- Stefanie Krug
- Department of Biology and Program in Neuroscience and Behavior, University of Massachusetts, Amherst, MA 01003, USA
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