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Non-image-forming light driven functions are preserved in a mouse model of autosomal dominant optic atrophy.

Perganta G, Barnard AR, Katti C, Vachtsevanos A, Douglas RH, MacLaren RE, Votruba M, Sekaran S - PLoS ONE (2013)

Bottom Line: There were no significant differences in any parameter tested relative to wildtype littermate controls.Furthermore, there was no significant difference in the number of melanopsin-expressing RGCs, cell morphology or melanopsin transcript levels between genotypes.The results provide support to growing evidence that the melanopsin-expressing RGCs are protected in mitochondrial optic neuropathies.

View Article: PubMed Central - PubMed

Affiliation: Nuffield Department of Clinical Neurosciences, Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, United Kingdom.

ABSTRACT
Autosomal dominant optic atrophy (ADOA) is a slowly progressive optic neuropathy that has been associated with mutations of the OPA1 gene. In patients, the disease primarily affects the retinal ganglion cells (RGCs) and causes optic nerve atrophy and visual loss. A subset of RGCs are intrinsically photosensitive, express the photopigment melanopsin and drive non-image-forming (NIF) visual functions including light driven circadian and sleep behaviours and the pupil light reflex. Given the RGC pathology in ADOA, disruption of NIF functions might be predicted. Interestingly in ADOA patients the pupil light reflex was preserved, although NIF behavioural outputs were not examined. The B6; C3-Opa1(Q285STOP) mouse model of ADOA displays optic nerve abnormalities, RGC dendropathy and functional visual disruption. We performed a comprehensive assessment of light driven NIF functions in this mouse model using wheel running activity monitoring, videotracking and pupillometry. Opa1 mutant mice entrained their activity rhythm to the external light/dark cycle, suppressed their activity in response to acute light exposure at night, generated circadian phase shift responses to 480 nm and 525 nm pulses, demonstrated immobility-defined sleep induction following exposure to a brief light pulse at night and exhibited an intensity dependent pupil light reflex. There were no significant differences in any parameter tested relative to wildtype littermate controls. Furthermore, there was no significant difference in the number of melanopsin-expressing RGCs, cell morphology or melanopsin transcript levels between genotypes. Taken together, these findings suggest the preservation of NIF functions in Opa1 mutants. The results provide support to growing evidence that the melanopsin-expressing RGCs are protected in mitochondrial optic neuropathies.

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Melanopsin expression in Opa1+/+ and Opa1+/− retinae.Overall distribution of melanopsin-positive RGCs in a flatmount retina from (A) Opa1+/+ and (B) Opa1+/− mice. The total number of melanopsin expressing cells was not significantly different between genotypes (Opa1+/+: n = 3; Opa1+/: n = 3). (C) Quantification of melanopsin (Opn4) and Opa1 gene expression by real time quantitative PCR. Expression levels in Opa1+/− animals are plotted relative to wildtype data. No significant difference in expression was detected for Opn4 between genotypes. A significant reduction in Opa1 expression was observed in Opa1+/− mice relative to wildtype controls (student's t-test. * = p<0.005). (D) Representative confocal images of melanopsin cells in Opa1+/+ and Opa1+/− retinae. A projected image of a confocal stack (from the inner plexiform layer to the ganglion cell layer) is shown for each genotype. An image at the plane of the outermost region of sublamina a and an image at the plane of the innermost region of sublamina b from the same image stacks is also shown.
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pone-0056350-g006: Melanopsin expression in Opa1+/+ and Opa1+/− retinae.Overall distribution of melanopsin-positive RGCs in a flatmount retina from (A) Opa1+/+ and (B) Opa1+/− mice. The total number of melanopsin expressing cells was not significantly different between genotypes (Opa1+/+: n = 3; Opa1+/: n = 3). (C) Quantification of melanopsin (Opn4) and Opa1 gene expression by real time quantitative PCR. Expression levels in Opa1+/− animals are plotted relative to wildtype data. No significant difference in expression was detected for Opn4 between genotypes. A significant reduction in Opa1 expression was observed in Opa1+/− mice relative to wildtype controls (student's t-test. * = p<0.005). (D) Representative confocal images of melanopsin cells in Opa1+/+ and Opa1+/− retinae. A projected image of a confocal stack (from the inner plexiform layer to the ganglion cell layer) is shown for each genotype. An image at the plane of the outermost region of sublamina a and an image at the plane of the innermost region of sublamina b from the same image stacks is also shown.

Mentions: Melanopsin cells were assessed immunohistologically in retinal wholemounts (Figure 6A,B). There was no significant difference in the total number of melanopsin cells between genotypes (average cell count per retina: Opa1+/+: 900±28.9 cells; Opa1+/−: 810±37.9 cells). Morphological characterisation of the melanopsin cells also revealed no significant difference in the mean soma diameter (Opa1+/+: 13.9±0.5 µm, n = 30; Opa1+/−: 14.0±0.5 µm, n = 30; data not shown). Furthermore, we observed no obvious differences in the stratification patterns of the melanopsin cells between genotypes (Figure 6C). Melanopsin positive dendrites were observed in both sublamina a (OFF) and sublamina b (ON) of the innerplexiform layer. Finally, there was no significant difference in melanopsin transcript levels between Opa1+/+ and Opa1+/− retinae (Figure 6D). As a control, we assessed Opa1 transcript levels and found an ∼50% reduction in Opa1+/− retinae relative to wildtype controls_ (p<0.005) as expected[8], [9].


Non-image-forming light driven functions are preserved in a mouse model of autosomal dominant optic atrophy.

Perganta G, Barnard AR, Katti C, Vachtsevanos A, Douglas RH, MacLaren RE, Votruba M, Sekaran S - PLoS ONE (2013)

Melanopsin expression in Opa1+/+ and Opa1+/− retinae.Overall distribution of melanopsin-positive RGCs in a flatmount retina from (A) Opa1+/+ and (B) Opa1+/− mice. The total number of melanopsin expressing cells was not significantly different between genotypes (Opa1+/+: n = 3; Opa1+/: n = 3). (C) Quantification of melanopsin (Opn4) and Opa1 gene expression by real time quantitative PCR. Expression levels in Opa1+/− animals are plotted relative to wildtype data. No significant difference in expression was detected for Opn4 between genotypes. A significant reduction in Opa1 expression was observed in Opa1+/− mice relative to wildtype controls (student's t-test. * = p<0.005). (D) Representative confocal images of melanopsin cells in Opa1+/+ and Opa1+/− retinae. A projected image of a confocal stack (from the inner plexiform layer to the ganglion cell layer) is shown for each genotype. An image at the plane of the outermost region of sublamina a and an image at the plane of the innermost region of sublamina b from the same image stacks is also shown.
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Related In: Results  -  Collection

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pone-0056350-g006: Melanopsin expression in Opa1+/+ and Opa1+/− retinae.Overall distribution of melanopsin-positive RGCs in a flatmount retina from (A) Opa1+/+ and (B) Opa1+/− mice. The total number of melanopsin expressing cells was not significantly different between genotypes (Opa1+/+: n = 3; Opa1+/: n = 3). (C) Quantification of melanopsin (Opn4) and Opa1 gene expression by real time quantitative PCR. Expression levels in Opa1+/− animals are plotted relative to wildtype data. No significant difference in expression was detected for Opn4 between genotypes. A significant reduction in Opa1 expression was observed in Opa1+/− mice relative to wildtype controls (student's t-test. * = p<0.005). (D) Representative confocal images of melanopsin cells in Opa1+/+ and Opa1+/− retinae. A projected image of a confocal stack (from the inner plexiform layer to the ganglion cell layer) is shown for each genotype. An image at the plane of the outermost region of sublamina a and an image at the plane of the innermost region of sublamina b from the same image stacks is also shown.
Mentions: Melanopsin cells were assessed immunohistologically in retinal wholemounts (Figure 6A,B). There was no significant difference in the total number of melanopsin cells between genotypes (average cell count per retina: Opa1+/+: 900±28.9 cells; Opa1+/−: 810±37.9 cells). Morphological characterisation of the melanopsin cells also revealed no significant difference in the mean soma diameter (Opa1+/+: 13.9±0.5 µm, n = 30; Opa1+/−: 14.0±0.5 µm, n = 30; data not shown). Furthermore, we observed no obvious differences in the stratification patterns of the melanopsin cells between genotypes (Figure 6C). Melanopsin positive dendrites were observed in both sublamina a (OFF) and sublamina b (ON) of the innerplexiform layer. Finally, there was no significant difference in melanopsin transcript levels between Opa1+/+ and Opa1+/− retinae (Figure 6D). As a control, we assessed Opa1 transcript levels and found an ∼50% reduction in Opa1+/− retinae relative to wildtype controls_ (p<0.005) as expected[8], [9].

Bottom Line: There were no significant differences in any parameter tested relative to wildtype littermate controls.Furthermore, there was no significant difference in the number of melanopsin-expressing RGCs, cell morphology or melanopsin transcript levels between genotypes.The results provide support to growing evidence that the melanopsin-expressing RGCs are protected in mitochondrial optic neuropathies.

View Article: PubMed Central - PubMed

Affiliation: Nuffield Department of Clinical Neurosciences, Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, United Kingdom.

ABSTRACT
Autosomal dominant optic atrophy (ADOA) is a slowly progressive optic neuropathy that has been associated with mutations of the OPA1 gene. In patients, the disease primarily affects the retinal ganglion cells (RGCs) and causes optic nerve atrophy and visual loss. A subset of RGCs are intrinsically photosensitive, express the photopigment melanopsin and drive non-image-forming (NIF) visual functions including light driven circadian and sleep behaviours and the pupil light reflex. Given the RGC pathology in ADOA, disruption of NIF functions might be predicted. Interestingly in ADOA patients the pupil light reflex was preserved, although NIF behavioural outputs were not examined. The B6; C3-Opa1(Q285STOP) mouse model of ADOA displays optic nerve abnormalities, RGC dendropathy and functional visual disruption. We performed a comprehensive assessment of light driven NIF functions in this mouse model using wheel running activity monitoring, videotracking and pupillometry. Opa1 mutant mice entrained their activity rhythm to the external light/dark cycle, suppressed their activity in response to acute light exposure at night, generated circadian phase shift responses to 480 nm and 525 nm pulses, demonstrated immobility-defined sleep induction following exposure to a brief light pulse at night and exhibited an intensity dependent pupil light reflex. There were no significant differences in any parameter tested relative to wildtype littermate controls. Furthermore, there was no significant difference in the number of melanopsin-expressing RGCs, cell morphology or melanopsin transcript levels between genotypes. Taken together, these findings suggest the preservation of NIF functions in Opa1 mutants. The results provide support to growing evidence that the melanopsin-expressing RGCs are protected in mitochondrial optic neuropathies.

Show MeSH
Related in: MedlinePlus