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Long-term and age-dependent restoration of visual function in a mouse model of CNGB3-associated achromatopsia following gene therapy.

Carvalho LS, Xu J, Pearson RA, Smith AJ, Bainbridge JW, Morris LM, Fliesler SJ, Ding XQ, Ali RR - Hum. Mol. Genet. (2011)

Bottom Line: Following subretinal delivery of the vector, CNGB3 was detected in both M- and S-cones and resulted in increased levels of CNGA3, increased cone density and survival, improved cone outer segment structure and normal subcellular compartmentalization of cone opsins.Therapy also resulted in long-term improvement of retinal function, with restoration of cone ERG amplitudes of up to 90% of wild-type and a significant improvement in visual acuity.Remarkably, successful restoration of cone function was observed even when treatment was initiated at 6 months of age; however, restoration of normal visual acuity was only possible in younger animals (e.g. 2-4 weeks old).

View Article: PubMed Central - PubMed

Affiliation: The Department of Genetics, UCL Institute of Ophthalmology, London, UK.

ABSTRACT
Mutations in the CNGB3 gene account for >50% of all known cases of achromatopsia. Although of early onset, its stationary character and the potential for rapid assessment of restoration of retinal function following therapy renders achromatopsia a very attractive candidate for gene therapy. Here we tested the efficacy of an rAAV2/8 vector containing a human cone arrestin promoter and a human CNGB3 cDNA in CNGB3 deficient mice. Following subretinal delivery of the vector, CNGB3 was detected in both M- and S-cones and resulted in increased levels of CNGA3, increased cone density and survival, improved cone outer segment structure and normal subcellular compartmentalization of cone opsins. Therapy also resulted in long-term improvement of retinal function, with restoration of cone ERG amplitudes of up to 90% of wild-type and a significant improvement in visual acuity. Remarkably, successful restoration of cone function was observed even when treatment was initiated at 6 months of age; however, restoration of normal visual acuity was only possible in younger animals (e.g. 2-4 weeks old). This study represents achievement of the most substantial restoration of visual function reported to date in an animal model of achromatopsia using a human gene construct, which has the potential to be utilized in clinical trials.

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Improved visual acuity in Cngb3−/− mice following gene therapy. Visual acuity and contrast sensitivity measurements taken at 60 days post-injection from the Cngb3−/− animals treated at P30 and P180. (A) Schematic showing the Optomotry© set-up. The mouse sits on a platform surrounded by four computer screens, which project a rotating sinusoidal striped grating. Involuntary reflex head-tracking responses are driven by the left (clockwise rotations, black arrow) and right (counter-clockwise rotations, white arrow) eyes, respectively. (B) The set up permits two measures of visual function, contrast sensitivity and visual acuity. (C) Visual acuity is restored to wild-type levels in the eyes treated at P30 (top left panel) but not in the eyes treated at P180 (top right panel). Response of the untreated eye remained at ∼85–80% of wild-type level. Contrast sensitivity (lower panels) remained the same between treated, untreated and wild-type eyes for both P30 and P180 treated animals. Data are representative as means ± SD of measurements of 11 and 6 eyes for the treated and untreated groups for P30 and P180, respectively, and 12 eyes for wild-type controls. Paired Student's t-test was used to determine significance (P< 0.001).
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DDR218F7: Improved visual acuity in Cngb3−/− mice following gene therapy. Visual acuity and contrast sensitivity measurements taken at 60 days post-injection from the Cngb3−/− animals treated at P30 and P180. (A) Schematic showing the Optomotry© set-up. The mouse sits on a platform surrounded by four computer screens, which project a rotating sinusoidal striped grating. Involuntary reflex head-tracking responses are driven by the left (clockwise rotations, black arrow) and right (counter-clockwise rotations, white arrow) eyes, respectively. (B) The set up permits two measures of visual function, contrast sensitivity and visual acuity. (C) Visual acuity is restored to wild-type levels in the eyes treated at P30 (top left panel) but not in the eyes treated at P180 (top right panel). Response of the untreated eye remained at ∼85–80% of wild-type level. Contrast sensitivity (lower panels) remained the same between treated, untreated and wild-type eyes for both P30 and P180 treated animals. Data are representative as means ± SD of measurements of 11 and 6 eyes for the treated and untreated groups for P30 and P180, respectively, and 12 eyes for wild-type controls. Paired Student's t-test was used to determine significance (P< 0.001).

Mentions: Untreated Cngb3−/− mice have already been shown to have decreased visual acuity as assessed by observing their optomotor responses under photopic conditions (31). As shown earlier, ERG responses demonstrated that functional improvement at the retinal level was possible in both P30 and P180 treated animals, but whether both groups would have the necessary plasticity to restore appropriate behavioral responses was unclear. We therefore examined whether supplementation of the CNGB3 transgene could improve visual acuity. Two groups of treated Cngb3−/− mice (injected at P30 and P180) were tested for their optomotor response (Fig. 7A and B) to examine whether age at treatment had any impact on visual function. As shown in Figure 7C, untreated animals have a significantly lower visual acuity than wild-type (untreated: 0.410 ± SD cycles/degree; n = 11; wild-type: 0.525 ± SD cycles/degree; n = 6; P< 0.01), consistent with a prior report (31). However, after treatment, visual acuity in the P30-treated animals was restored to a similar level (0.520 ± SD cycles/degree; n = 11) as that observed in wild-type animals (0.525 ± SD cycles/degree; n = 6; P= 0.83) In contrast, we observed no significant difference in visual acuity between the treated and untreated eyes in the P180 group (wild-type: 0.510 ± SD cycles/degree; treated: 0.438 ± SD cycles/degree; untreated: 0.410 ± SD cycles/degree; n = 6; P= 0.58), indicating that treatment received at an older age is less capable of restoring visual acuity. There was no statistical difference in contrast sensitivity between wild-type and treated and untreated Cngb3−/− eyes for the either the P30 or P180 groups (Fig. 7C; P> 0.27). Therefore, the results presented here show that visual acuity can be restored in Cngb3−/− mice by administration of rAAV2/8_hCAR_hCNGB3, but there is an inverse correlation between the age of treatment and the degree of improvement in visual function (i.e. the older the age of treatment initiation, the worse the visual function outcome).Figure 7.


Long-term and age-dependent restoration of visual function in a mouse model of CNGB3-associated achromatopsia following gene therapy.

Carvalho LS, Xu J, Pearson RA, Smith AJ, Bainbridge JW, Morris LM, Fliesler SJ, Ding XQ, Ali RR - Hum. Mol. Genet. (2011)

Improved visual acuity in Cngb3−/− mice following gene therapy. Visual acuity and contrast sensitivity measurements taken at 60 days post-injection from the Cngb3−/− animals treated at P30 and P180. (A) Schematic showing the Optomotry© set-up. The mouse sits on a platform surrounded by four computer screens, which project a rotating sinusoidal striped grating. Involuntary reflex head-tracking responses are driven by the left (clockwise rotations, black arrow) and right (counter-clockwise rotations, white arrow) eyes, respectively. (B) The set up permits two measures of visual function, contrast sensitivity and visual acuity. (C) Visual acuity is restored to wild-type levels in the eyes treated at P30 (top left panel) but not in the eyes treated at P180 (top right panel). Response of the untreated eye remained at ∼85–80% of wild-type level. Contrast sensitivity (lower panels) remained the same between treated, untreated and wild-type eyes for both P30 and P180 treated animals. Data are representative as means ± SD of measurements of 11 and 6 eyes for the treated and untreated groups for P30 and P180, respectively, and 12 eyes for wild-type controls. Paired Student's t-test was used to determine significance (P< 0.001).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3140821&req=5

DDR218F7: Improved visual acuity in Cngb3−/− mice following gene therapy. Visual acuity and contrast sensitivity measurements taken at 60 days post-injection from the Cngb3−/− animals treated at P30 and P180. (A) Schematic showing the Optomotry© set-up. The mouse sits on a platform surrounded by four computer screens, which project a rotating sinusoidal striped grating. Involuntary reflex head-tracking responses are driven by the left (clockwise rotations, black arrow) and right (counter-clockwise rotations, white arrow) eyes, respectively. (B) The set up permits two measures of visual function, contrast sensitivity and visual acuity. (C) Visual acuity is restored to wild-type levels in the eyes treated at P30 (top left panel) but not in the eyes treated at P180 (top right panel). Response of the untreated eye remained at ∼85–80% of wild-type level. Contrast sensitivity (lower panels) remained the same between treated, untreated and wild-type eyes for both P30 and P180 treated animals. Data are representative as means ± SD of measurements of 11 and 6 eyes for the treated and untreated groups for P30 and P180, respectively, and 12 eyes for wild-type controls. Paired Student's t-test was used to determine significance (P< 0.001).
Mentions: Untreated Cngb3−/− mice have already been shown to have decreased visual acuity as assessed by observing their optomotor responses under photopic conditions (31). As shown earlier, ERG responses demonstrated that functional improvement at the retinal level was possible in both P30 and P180 treated animals, but whether both groups would have the necessary plasticity to restore appropriate behavioral responses was unclear. We therefore examined whether supplementation of the CNGB3 transgene could improve visual acuity. Two groups of treated Cngb3−/− mice (injected at P30 and P180) were tested for their optomotor response (Fig. 7A and B) to examine whether age at treatment had any impact on visual function. As shown in Figure 7C, untreated animals have a significantly lower visual acuity than wild-type (untreated: 0.410 ± SD cycles/degree; n = 11; wild-type: 0.525 ± SD cycles/degree; n = 6; P< 0.01), consistent with a prior report (31). However, after treatment, visual acuity in the P30-treated animals was restored to a similar level (0.520 ± SD cycles/degree; n = 11) as that observed in wild-type animals (0.525 ± SD cycles/degree; n = 6; P= 0.83) In contrast, we observed no significant difference in visual acuity between the treated and untreated eyes in the P180 group (wild-type: 0.510 ± SD cycles/degree; treated: 0.438 ± SD cycles/degree; untreated: 0.410 ± SD cycles/degree; n = 6; P= 0.58), indicating that treatment received at an older age is less capable of restoring visual acuity. There was no statistical difference in contrast sensitivity between wild-type and treated and untreated Cngb3−/− eyes for the either the P30 or P180 groups (Fig. 7C; P> 0.27). Therefore, the results presented here show that visual acuity can be restored in Cngb3−/− mice by administration of rAAV2/8_hCAR_hCNGB3, but there is an inverse correlation between the age of treatment and the degree of improvement in visual function (i.e. the older the age of treatment initiation, the worse the visual function outcome).Figure 7.

Bottom Line: Following subretinal delivery of the vector, CNGB3 was detected in both M- and S-cones and resulted in increased levels of CNGA3, increased cone density and survival, improved cone outer segment structure and normal subcellular compartmentalization of cone opsins.Therapy also resulted in long-term improvement of retinal function, with restoration of cone ERG amplitudes of up to 90% of wild-type and a significant improvement in visual acuity.Remarkably, successful restoration of cone function was observed even when treatment was initiated at 6 months of age; however, restoration of normal visual acuity was only possible in younger animals (e.g. 2-4 weeks old).

View Article: PubMed Central - PubMed

Affiliation: The Department of Genetics, UCL Institute of Ophthalmology, London, UK.

ABSTRACT
Mutations in the CNGB3 gene account for >50% of all known cases of achromatopsia. Although of early onset, its stationary character and the potential for rapid assessment of restoration of retinal function following therapy renders achromatopsia a very attractive candidate for gene therapy. Here we tested the efficacy of an rAAV2/8 vector containing a human cone arrestin promoter and a human CNGB3 cDNA in CNGB3 deficient mice. Following subretinal delivery of the vector, CNGB3 was detected in both M- and S-cones and resulted in increased levels of CNGA3, increased cone density and survival, improved cone outer segment structure and normal subcellular compartmentalization of cone opsins. Therapy also resulted in long-term improvement of retinal function, with restoration of cone ERG amplitudes of up to 90% of wild-type and a significant improvement in visual acuity. Remarkably, successful restoration of cone function was observed even when treatment was initiated at 6 months of age; however, restoration of normal visual acuity was only possible in younger animals (e.g. 2-4 weeks old). This study represents achievement of the most substantial restoration of visual function reported to date in an animal model of achromatopsia using a human gene construct, which has the potential to be utilized in clinical trials.

Show MeSH
Related in: MedlinePlus