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Inducible ablation of melanopsin-expressing retinal ganglion cells reveals their central role in non-image forming visual responses. PLoS One 2008; 3:e2451. [PMID: 18545654 PMCID: PMC2396502 DOI: 10.1371/journal.pone.0002451] [Citation(s) in RCA: 213] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Accepted: 05/14/2008] [Indexed: 12/26/2022] Open
Abstract
Rod/cone photoreceptors of the outer retina and the melanopsin-expressing retinal ganglion cells (mRGCs) of the inner retina mediate non-image forming visual responses including entrainment of the circadian clock to the ambient light, the pupillary light reflex (PLR), and light modulation of activity. Targeted deletion of the melanopsin gene attenuates these adaptive responses with no apparent change in the development and morphology of the mRGCs. Comprehensive identification of mRGCs and knowledge of their specific roles in image-forming and non-image forming photoresponses are currently lacking. We used a Cre-dependent GFP expression strategy in mice to genetically label the mRGCs. This revealed that only a subset of mRGCs express enough immunocytochemically detectable levels of melanopsin. We also used a Cre-inducible diphtheria toxin receptor (iDTR) expression approach to express the DTR in mRGCs. mRGCs develop normally, but can be acutely ablated upon diphtheria toxin administration. The mRGC-ablated mice exhibited normal outer retinal function. However, they completely lacked non-image forming visual responses such as circadian photoentrainment, light modulation of activity, and PLR. These results point to the mRGCs as the site of functional integration of the rod/cone and melanopsin phototransduction pathways and as the primary anatomical site for the divergence of image-forming and non-image forming photoresponses in mammals.
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Siepka SM, Yoo SH, Park J, Song W, Kumar V, Hu Y, Lee C, Takahashi JS. Circadian mutant Overtime reveals F-box protein FBXL3 regulation of cryptochrome and period gene expression. Cell 2007; 129:1011-23. [PMID: 17462724 PMCID: PMC3762874 DOI: 10.1016/j.cell.2007.04.030] [Citation(s) in RCA: 402] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2007] [Revised: 04/02/2007] [Accepted: 04/09/2007] [Indexed: 11/29/2022]
Abstract
Using a forward genetics ENU mutagenesis screen for recessive mutations that affect circadian rhythmicity in the mouse, we isolated a long period (approximately 26 hr) circadian mutant named Overtime (Ovtm). Positional cloning and genetic complementation reveal that Ovtm is encoded by the F-box protein FBXL3, a component of the SKP1-CUL1-F-box-protein (SCF) E3 ubiquitin ligase complex. The Ovtm mutation causes an isoleucine to threonine (I364T) substitution leading to a loss of function in FBXL3, which interacts specifically with the CRYPTOCHROME (CRY) proteins. In Ovtm mice, expression of the PERIOD proteins PER1 and PER2 is reduced; however, the CRY proteins CRY1 and CRY2 are unchanged. The loss of FBXL3 function leads to a stabilization of the CRY proteins, which in turn leads to a global transcriptional repression of the Per and Cry genes. Thus, Fbxl3(Ovtm) defines a molecular link between CRY turnover and CLOCK/BMAL1-dependent circadian transcription to modulate circadian period.
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Affiliation(s)
- Sandra M. Siepka
- Howard Hughes Medical Institute, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
- Center for Functional Genomics, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
| | - Seung-Hee Yoo
- Center for Functional Genomics, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
| | - Junghea Park
- Center for Functional Genomics, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
| | - Weimin Song
- Howard Hughes Medical Institute, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
| | - Vivek Kumar
- Howard Hughes Medical Institute, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
- Center for Functional Genomics, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
| | - Yinin Hu
- Center for Functional Genomics, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
| | - Choogon Lee
- Department of Biological Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306, USA
| | - Joseph S. Takahashi
- Howard Hughes Medical Institute, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
- Center for Functional Genomics, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
- Department of Neurobiology and Physiology, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
- To whom correspondence should be addressed. Contact: Joseph S. Takahashi, , Phone: 847-491-4605. Fax: 847-491-4600
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Meredith AL, Wiler SW, Miller BH, Takahashi JS, Fodor AA, Ruby NF, Aldrich RW. BK calcium-activated potassium channels regulate circadian behavioral rhythms and pacemaker output. Nat Neurosci 2006; 9:1041-9. [PMID: 16845385 PMCID: PMC2909323 DOI: 10.1038/nn1740] [Citation(s) in RCA: 192] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2006] [Accepted: 06/20/2006] [Indexed: 01/02/2023]
Abstract
Spontaneous action potentials in the suprachiasmatic nucleus (SCN) are necessary for normal circadian timing of behavior in mammals. The SCN exhibits a daily oscillation in spontaneous firing rate (SFR), but the ionic conductances controlling SFR and the relationship of SFR to subsequent circadian behavioral rhythms are not understood. We show that daily expression of the large conductance Ca(2+)-activated K(+) channel (BK) in the SCN is controlled by the intrinsic circadian clock. BK channel-null mice (Kcnma1(-/-)) have increased SFRs in SCN neurons selectively at night and weak circadian amplitudes in multiple behaviors timed by the SCN. Kcnma1(-/-) mice show normal expression of clock genes such as Arntl (Bmal1), indicating a role for BK channels in SCN pacemaker output, rather than in intrinsic time-keeping. Our findings implicate BK channels as important regulators of the SFR and suggest that the SCN pacemaker governs the expression of circadian behavioral rhythms through SFR modulation.
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Affiliation(s)
- Andrea L Meredith
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA.
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Vitaterna MH, Pinto LH, Takahashi JS. Large-scale mutagenesis and phenotypic screens for the nervous system and behavior in mice. Trends Neurosci 2006; 29:233-40. [PMID: 16519954 PMCID: PMC3761413 DOI: 10.1016/j.tins.2006.02.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Revised: 12/20/2005] [Accepted: 02/17/2006] [Indexed: 11/20/2022]
Abstract
Significant developments have occurred in our understanding of the mammalian genome thanks to informatics, expression profiling and sequencing of the human and rodent genomes. However, although these facets of genomic analysis are being addressed, analysis of in vivo gene function remains a formidable task. Evaluation of the phenotype of mutants provides powerful access to gene function, and this approach is particularly relevant to the nervous system and behavior. Here, we discuss the complementary mouse genetic approaches of gene-driven, targeted mutagenesis and phenotype-driven, chemical mutagenesis. We highlight an NIH-supported large-scale effort to use phenotype-driven mutagenesis screens to identify mouse mutants with neural and behavioral alterations. Such single-gene mutations can then be used for gene identification using positional candidate gene-cloning methods.
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Affiliation(s)
- Martha Hotz Vitaterna
- Center for Functional Genomics and Department of Neurobiology and Physiology, Northwestern University, Evanston, IL 60208, USA
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