A codon-optimized Mecp2 transgene corrects breathing deficits and improves survival in a mouse model of Rett syndrome

Matagne, Valérie; Ehinger, Yann; Saidi, Lydia; Borges-Correia, Ana; Barkats, Martine; Bartoli, Marc; Villard, Laurent; Roux, Jean‐Christophe

doi:10.1016/j.nbd.2016.12.009

Cited by 39 publications

(42 citation statements)

References 53 publications

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“…Importantly, however, intracisternal administration of 1 × 10 12 vg AAV9/ hMECP2 (v1) still resulted in potentially problematic peripheral transgene expression (Figure 2), a trend toward elevated blood serum toxicity indicators (Figure S2), and deleterious neurological side effects (Figures 1 and 3), which were not seen in mice treated with an AAV9/EGFP control vector. Increased severity of hindlimb clasping and abnormal gait were unexpected, given the absence of these side effects in previously published MeCP2 gene transfer studies 11, 12, 32. In light of these data, our conclusion is that AAV9/ hMECP2 (v1) cannot move forward in translational studies.…”

Section: Discussionmentioning

confidence: 60%

Improved MECP2 Gene Therapy Extends the Survival of MeCP2-Null Mice without Apparent Toxicity after Intracisternal Delivery

Sinnett

Hector

Gadalla

et al. 2017

Molecular Therapy - Methods & Clinical Development

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Intravenous administration of adeno-associated virus serotype 9 (AAV9)/hMECP2 has been shown to extend the lifespan of Mecp2−/y mice, but this delivery route induces liver toxicity in wild-type (WT) mice. To reduce peripheral transgene expression, we explored the safety and efficacy of AAV9/hMECP2 injected into the cisterna magna (ICM). AAV9/hMECP2 (1 × 1012 viral genomes [vg]; ICM) extended Mecp2−/y survival but aggravated hindlimb clasping and abnormal gait phenotypes. In WT mice, 1 × 1012 vg of AAV9/hMECP2 induced clasping and abnormal gait. A lower dose mitigated these adverse phenotypes but failed to extend survival of Mecp2−/y mice. Thus, ICM delivery of this vector is impractical as a treatment for Rett syndrome (RTT). To improve the safety of MeCP2 gene therapy, the gene expression cassette was modified to include more endogenous regulatory elements believed to modulate MeCP2 expression in vivo. In Mecp2−/y mice, ICM injection of the modified vector extended lifespan and was well tolerated by the liver but did not rescue RTT behavioral phenotypes. In WT mice, these same doses of the modified vector had no adverse effects on survival or neurological phenotypes. In summary, we identified limitations of the original vector and demonstrated that an improved vector design extends Mecp2−/y survival, without apparent toxicity.

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Section: Discussionmentioning

confidence: 60%

Improved MECP2 Gene Therapy Extends the Survival of MeCP2-Null Mice without Apparent Toxicity after Intracisternal Delivery

Sinnett

Hector

Gadalla

et al. 2017

Molecular Therapy - Methods & Clinical Development

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“…Recent attempts to deliver MECP2 exogenously in mouse models of RTT used widely varying vector doses but are difficult to compare based on additional differences in cassette design and other variables, including viral production, dosing protocol, and phenotype measures 19, 20, 21. In the present study, we used our previously published cassette design (human MECP2_e1 , under the control of a MeP229 core promoter fragment) 19 to directly investigate the effect of dose in terms of efficacy and safety.…”

Section: Discussionmentioning

confidence: 99%

“…Previous preclinical RTT gene therapy studies19, 20, 21 have focused on using the Mecp2 − /y model to screen for vector efficacy and potential toxicity. However, the presence of mutant endogenous MeCP2 could potentially produce a quasi-dominant negative action on the vector-derived MeCP2.…”

Section: Discussionmentioning

confidence: 99%

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Development of a Novel AAV Gene Therapy Cassette with Improved Safety Features and Efficacy in a Mouse Model of Rett Syndrome

Gadalla

Vudhironarit

Hector

et al. 2017

Molecular Therapy - Methods & Clinical Development

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Rett syndrome (RTT), caused by loss-of-function mutations in the MECP2 gene, is a neurological disorder characterized by severe impairment of motor and cognitive functions. The aim of this study was to investigate the impact of vector design, dosage, and delivery route on the efficacy and safety of gene augmentation therapy in mouse models of RTT. Our results show that AAV-mediated delivery of MECP2 to Mecp2 null mice by systemic administration, and utilizing a minimal endogenous promoter, was associated with a narrow therapeutic window and resulted in liver toxicity at higher doses. Lower doses of this vector significantly extended the survival of mice lacking MeCP2 or expressing a mutant T158M allele but had no impact on RTT-like neurological phenotypes. Modifying vector design by incorporating an extended Mecp2 promoter and additional regulatory 3′ UTR elements significantly reduced hepatic toxicity after systemic administration. Moreover, direct cerebroventricular injection of this vector into neonatal Mecp2-null mice resulted in high brain transduction efficiency, increased survival and body weight, and an amelioration of RTT-like phenotypes. Our results show that controlling levels of MeCP2 expression in the liver is achievable through modification of the expression cassette. However, it also highlights the importance of achieving high brain transduction to impact the RTT-like phenotypes.

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“…Thus, a successful gene therapy for RTT has to deliver the correct MeCP2 dosage in a tight range that overlaps with endogenous levels. Different studies have recently provided encouraging results showing that intravenous administration of an Adeno-associated virus serotype 9 (AAV9) expressing the wild-type (WT) MECP2 attenuated neurological dysfunctions and extended lifespan in RTT mice [14][15][16][17] . However, the AAV9 does not cross efficiently the blood-brain barrier in adult mice while having a preferential tropism for peripheral organs.…”

Section: Introductionmentioning

confidence: 99%

Whole brain delivery of an instability-proneMecp2transgene improves behavioral and molecular pathological defects in mouse models of Rett syndrome

Luoni

Giannelli

Indrigo

et al. 2019

Preprint

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Rett syndrome (RTT) is an incurable neurodevelopmental disorder caused by mutations inthe gene encoding for methyl-CpG binding-protein 2 (MeCP2). Gene therapy for this disease presents inherent hurdles since MECP2 is expressed throughout the brain and its duplication leads to severe neurological conditions as well. However, the recent introduction of AAV-PHP.eB, an engineered capsid with an unprecedented efficiency in crossing the blood-brain barrier upon intravenous injection, has provided an invaluable vehicle for gene transfer in the mouse nervous system. Herein, we use AAV-PHP.eB to deliver an instability-prone Mecp2 (iMecp2) transgene cassette which, increasing RNA destabilization and inefficient protein translation of the viral Mecp2 transgene, limits supraphysiological Mecp2 protein levels in transduced neural tissues. Intravenous injections of the PHP.eB-iMecp2 virus in symptomatic male and female Mecp2 mutant mice significantly ameliorated the disease progression with improved locomotor activity, coordination, lifespan and normalization of altered gene expression and mTOR signaling. Remarkably, PHP.eB-iMecp2 administration did not result in severe toxicity effects either in female Mecp2 mutant or in wild-type animals. In contrast, we observed a strong immune response to the transgene in treated male Mecp2 mutant mice that was overcome by immunosuppression. Overall, PHP.eB-mediated delivery of the iMecp2 cassette provided widespread and efficient gene transfer maintaining physiological Mecp2 protein levels in the brain. This combination defines a novel viral system with significant therapeutic efficacy and increased safety which can contribute to overcome the hurdles that are delaying clinical applications of gene therapy for RTT. One Sentence Summary: Global brain transduction of the instability-prone Mecp2 transgene by systemic AAV-PHP.eB administration is both safe and effective in protecting male and female Mecp2 mutant mice from the RTT disease phenotype. WT KO -GFP KO-iMeCP2-10 11 vg 4 8 12 16 20 24 28 32 36 40 0 50 100 Weeks Percent survival WT KO-GFP KO-iMecp2-10 11 vg KO-iMecp2-10 11 vg + Csa KO-GFP +Csa

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A codon-optimized Mecp2 transgene corrects breathing deficits and improves survival in a mouse model of Rett syndrome

Cited by 39 publications

References 53 publications

Improved MECP2 Gene Therapy Extends the Survival of MeCP2-Null Mice without Apparent Toxicity after Intracisternal Delivery

Improved MECP2 Gene Therapy Extends the Survival of MeCP2-Null Mice without Apparent Toxicity after Intracisternal Delivery

Development of a Novel AAV Gene Therapy Cassette with Improved Safety Features and Efficacy in a Mouse Model of Rett Syndrome

Whole brain delivery of an instability-proneMecp2transgene improves behavioral and molecular pathological defects in mouse models of Rett syndrome

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