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Mice deficient of glutamatergic signaling from intrinsically photosensitive retinal ganglion cells exhibit abnormal circadian photoentrainment.

Purrier N, Engeland WC, Kofuji P - PLoS ONE (2014)

Bottom Line: The relative contribution of each neurotransmitter system for the circadian photoentrainment and other NIF visual responses is still unresolved.Other NIF responses such as the PLR and negative masking responses to light were also partially attenuated.Overall, these results suggest that glutamate from ipRGCs drives circadian photoentrainment and negative masking responses to light.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States of America.

ABSTRACT
Several aspects of behavior and physiology, such as sleep and wakefulness, blood pressure, body temperature, and hormone secretion exhibit daily oscillations known as circadian rhythms. These circadian rhythms are orchestrated by an intrinsic biological clock in the suprachiasmatic nuclei (SCN) of the hypothalamus which is adjusted to the daily environmental cycles of day and night by the process of photoentrainment. In mammals, the neuronal signal for photoentrainment arises from a small subset of intrinsically photosensitive retinal ganglion cells (ipRGCs) that send a direct projection to the SCN. ipRGCs also mediate other non-image-forming (NIF) visual responses such as negative masking of locomotor activity by light, and the pupillary light reflex (PLR) via co-release of neurotransmitters glutamate and pituitary adenylate cyclase-activating peptide (PACAP) from their synaptic terminals. The relative contribution of each neurotransmitter system for the circadian photoentrainment and other NIF visual responses is still unresolved. We investigated the role of glutamatergic neurotransmission for circadian photoentrainment and NIF behaviors by selective ablation of ipRGC glutamatergic synaptic transmission in mice. Mutant mice displayed delayed re-entrainment to a 6 h phase shift (advance or delay) in the light cycle and incomplete photoentrainment in a symmetrical skeleton photoperiod regimen (1 h light pulses between 11 h dark periods). Circadian rhythmicity in constant darkness also was reduced in some mutant mice. Other NIF responses such as the PLR and negative masking responses to light were also partially attenuated. Overall, these results suggest that glutamate from ipRGCs drives circadian photoentrainment and negative masking responses to light.

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Ablation of VGLUT2 expression in Vglut2-cKO mouse retinas.(A) Diagram of gene targeting strategy. Mouse with exon 2 of Vglut2 gene flanked by LoxP sites was bred with the Opn4-Cre mouse line in which Cre was inserted in the Opn4 gene locus. Progeny contained mice with deletion of Vglut2 exon 2 in ipRGCs (Vglut2-cKO mice). (B) Retinal sections of Vglut2-cKO and control littermate stained for Opn4, VGLUT2. Notice the co-localization of VGLUT2 with Opn 4 (arrows) in the control but not in the Vglut2-cKO mice retinas. ONL, outer nuclear layer; INL, inner nuclear layer; IPL, inner plexiform layer; GCL, ganglion cell layer. Scale bar  = 50 µm.
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pone-0111449-g001: Ablation of VGLUT2 expression in Vglut2-cKO mouse retinas.(A) Diagram of gene targeting strategy. Mouse with exon 2 of Vglut2 gene flanked by LoxP sites was bred with the Opn4-Cre mouse line in which Cre was inserted in the Opn4 gene locus. Progeny contained mice with deletion of Vglut2 exon 2 in ipRGCs (Vglut2-cKO mice). (B) Retinal sections of Vglut2-cKO and control littermate stained for Opn4, VGLUT2. Notice the co-localization of VGLUT2 with Opn 4 (arrows) in the control but not in the Vglut2-cKO mice retinas. ONL, outer nuclear layer; INL, inner nuclear layer; IPL, inner plexiform layer; GCL, ganglion cell layer. Scale bar  = 50 µm.

Mentions: To examine the role of ipRGC glutamatergic neurotransmission for circadian photoentrainment and other NIF visual functions, we performed the conditional ablation of VGLUT2 in ipRGCs. Previous studies specified that VGLUT2 is the only vesicular transporter required for glutamate storage in synaptic vesicles of RGCs including ipRGCs [10], [17]. Ablation of VGLUT2 expression in ipRGCs was achieved by breeding Opn4Cre/Cre mice with Vglut2flx/flx mice (Figure 1A). The Opn4Cre/+, Vglut2flx/flx mice (hereafter designated as Vglut2-cKO) developed with no apparent gross behavioral abnormalities. Retinal projections to the brain in the Vglut2-cKO mouse line were apparently normal as assessed by unilateral intravitreal injection of cholera toxin B protein (CTB). CTB-labeled terminals were detected bilaterally in the SCN (Figure S1). In the lateral geniculate nucleus (LGN) of the thalamus, the dorsal domain is innervated mostly by retinal afferents from conventional RGCs while the ventral domain and the intergeniculate leaflet (IGL) receive afferents mostly from ipRGCs [26]. CTB labeling in the ventral domain of the LGN and the IGL indicated that ipRGC innervation is preserved in the Vglut2-cKO mouse (Figure S1). Other NIF visual centers such as the olivary pretectal nucleus, superior colliculus, peri-supraoptic nucleus, and subparaventricular zone of the hypothalamus were also labeled with CTB (data not shown). We also did not detect major structural changes in the SCN as assessed by vasoactive intestinal peptide (VIP) (Figure S2). In summary, ipRGCs in the Vglut2-cKO mouse innervate the expected target brain centers, and the SCN does not show obvious structural abnormalities.


Mice deficient of glutamatergic signaling from intrinsically photosensitive retinal ganglion cells exhibit abnormal circadian photoentrainment.

Purrier N, Engeland WC, Kofuji P - PLoS ONE (2014)

Ablation of VGLUT2 expression in Vglut2-cKO mouse retinas.(A) Diagram of gene targeting strategy. Mouse with exon 2 of Vglut2 gene flanked by LoxP sites was bred with the Opn4-Cre mouse line in which Cre was inserted in the Opn4 gene locus. Progeny contained mice with deletion of Vglut2 exon 2 in ipRGCs (Vglut2-cKO mice). (B) Retinal sections of Vglut2-cKO and control littermate stained for Opn4, VGLUT2. Notice the co-localization of VGLUT2 with Opn 4 (arrows) in the control but not in the Vglut2-cKO mice retinas. ONL, outer nuclear layer; INL, inner nuclear layer; IPL, inner plexiform layer; GCL, ganglion cell layer. Scale bar  = 50 µm.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4214747&req=5

pone-0111449-g001: Ablation of VGLUT2 expression in Vglut2-cKO mouse retinas.(A) Diagram of gene targeting strategy. Mouse with exon 2 of Vglut2 gene flanked by LoxP sites was bred with the Opn4-Cre mouse line in which Cre was inserted in the Opn4 gene locus. Progeny contained mice with deletion of Vglut2 exon 2 in ipRGCs (Vglut2-cKO mice). (B) Retinal sections of Vglut2-cKO and control littermate stained for Opn4, VGLUT2. Notice the co-localization of VGLUT2 with Opn 4 (arrows) in the control but not in the Vglut2-cKO mice retinas. ONL, outer nuclear layer; INL, inner nuclear layer; IPL, inner plexiform layer; GCL, ganglion cell layer. Scale bar  = 50 µm.
Mentions: To examine the role of ipRGC glutamatergic neurotransmission for circadian photoentrainment and other NIF visual functions, we performed the conditional ablation of VGLUT2 in ipRGCs. Previous studies specified that VGLUT2 is the only vesicular transporter required for glutamate storage in synaptic vesicles of RGCs including ipRGCs [10], [17]. Ablation of VGLUT2 expression in ipRGCs was achieved by breeding Opn4Cre/Cre mice with Vglut2flx/flx mice (Figure 1A). The Opn4Cre/+, Vglut2flx/flx mice (hereafter designated as Vglut2-cKO) developed with no apparent gross behavioral abnormalities. Retinal projections to the brain in the Vglut2-cKO mouse line were apparently normal as assessed by unilateral intravitreal injection of cholera toxin B protein (CTB). CTB-labeled terminals were detected bilaterally in the SCN (Figure S1). In the lateral geniculate nucleus (LGN) of the thalamus, the dorsal domain is innervated mostly by retinal afferents from conventional RGCs while the ventral domain and the intergeniculate leaflet (IGL) receive afferents mostly from ipRGCs [26]. CTB labeling in the ventral domain of the LGN and the IGL indicated that ipRGC innervation is preserved in the Vglut2-cKO mouse (Figure S1). Other NIF visual centers such as the olivary pretectal nucleus, superior colliculus, peri-supraoptic nucleus, and subparaventricular zone of the hypothalamus were also labeled with CTB (data not shown). We also did not detect major structural changes in the SCN as assessed by vasoactive intestinal peptide (VIP) (Figure S2). In summary, ipRGCs in the Vglut2-cKO mouse innervate the expected target brain centers, and the SCN does not show obvious structural abnormalities.

Bottom Line: The relative contribution of each neurotransmitter system for the circadian photoentrainment and other NIF visual responses is still unresolved.Other NIF responses such as the PLR and negative masking responses to light were also partially attenuated.Overall, these results suggest that glutamate from ipRGCs drives circadian photoentrainment and negative masking responses to light.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States of America.

ABSTRACT
Several aspects of behavior and physiology, such as sleep and wakefulness, blood pressure, body temperature, and hormone secretion exhibit daily oscillations known as circadian rhythms. These circadian rhythms are orchestrated by an intrinsic biological clock in the suprachiasmatic nuclei (SCN) of the hypothalamus which is adjusted to the daily environmental cycles of day and night by the process of photoentrainment. In mammals, the neuronal signal for photoentrainment arises from a small subset of intrinsically photosensitive retinal ganglion cells (ipRGCs) that send a direct projection to the SCN. ipRGCs also mediate other non-image-forming (NIF) visual responses such as negative masking of locomotor activity by light, and the pupillary light reflex (PLR) via co-release of neurotransmitters glutamate and pituitary adenylate cyclase-activating peptide (PACAP) from their synaptic terminals. The relative contribution of each neurotransmitter system for the circadian photoentrainment and other NIF visual responses is still unresolved. We investigated the role of glutamatergic neurotransmission for circadian photoentrainment and NIF behaviors by selective ablation of ipRGC glutamatergic synaptic transmission in mice. Mutant mice displayed delayed re-entrainment to a 6 h phase shift (advance or delay) in the light cycle and incomplete photoentrainment in a symmetrical skeleton photoperiod regimen (1 h light pulses between 11 h dark periods). Circadian rhythmicity in constant darkness also was reduced in some mutant mice. Other NIF responses such as the PLR and negative masking responses to light were also partially attenuated. Overall, these results suggest that glutamate from ipRGCs drives circadian photoentrainment and negative masking responses to light.

Show MeSH
Related in: MedlinePlus