Postnatal manipulation of Pax6 dosage reverses congenital tissue malformation defects.

The Journal of clinical investigation (Impact Factor: 15.39). 12/2013; DOI: 10.1172/JCI70462
Source: PubMed

ABSTRACT Aniridia is a congenital and progressive panocular condition with poor visual prognosis that is associated with brain, olfactory, and pancreatic abnormalities. Development of aniridia is linked with nonsense mutations that result in paired box 6 (PAX6) haploinsufficiency. Here, we used a mouse model of aniridia to test the hypothesis that manipulation of Pax6 dosage through a mutation-independent nonsense mutation suppression strategy would limit progressive, postnatal damage in the eye. We focused on the nonsense suppression drugs 3-[5-(2-fluorophenyl)-1,2,4-oxadiazol-3-yl]benzoic acid (ataluren) and gentamicin. Remarkably, we demonstrated that nonsense suppression not only inhibited disease progression but also stably reversed corneal, lens, and retinal malformation defects and restored electrical and behavioral responses of the retina. The most successful results were achieved through topical application of the drug formulation START (0.9% sodium chloride, 1% Tween 80, 1% powdered ataluren, 1% carboxymethylcellulose), which was designed to enhance particle dispersion and to increase suspension viscosity. These observations suggest that the eye retains marked developmental plasticity into the postnatal period and remains sensitive to molecular remodeling. Furthermore, these data indicate that other neurological developmental anomalies associated with dosage-sensitive genetic mutations may be reversible through nonsense suppression therapeutics.

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    ABSTRACT: Background: Dystrophinopathy is a rare, severe muscle disorder, and nonsense mutations are found in 13% of cases. Ataluren was developed to enable ribosomal readthrough of premature stop codons in nonsense mutation (nm) genetic disorders. Methods: Randomized, double-blind, placebo-controlled study; males ≥5 years with nm-dystrophinopathy received study drug orally 3 times daily, ataluren 10, 10, 20 mg/kg (N=57), ataluren 20, 20, 40 mg/kg (N=60), or placebo (N=57) for 48 weeks. The primary endpoint was change in 6-minute walk distance (6MWD) at Week 48. Results: Ataluren was generally well tolerated. The primary endpoint favored ataluren 10, 10, 20 mg/kg vs placebo; the week 48 6MWD ∆=31.3 meters, post-hoc P=0.056. Secondary endpoints (timed function tests) showed meaningful differences between ataluren 10, 10, 20 mg/kg and placebo. Conclusions: As the first investigational new drug targeting the underlying cause of nm-dystrophinopathy, ataluren offers promise as a treatment for this orphan genetic disorder with high unmet medical need. © 2014 Wiley Periodicals, Inc.
    Muscle & Nerve 07/2014; DOI:10.1002/mus.24332 · 2.31 Impact Factor
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    ABSTRACT: Congenital aniridia manifests in different forms: it can be transmitted in an autosomal dominant way, as sporadic aniridia and as part of several syndromes including WAGR (Wilms tumor, aniridia, genitourinary abnormalities and intellectual disability) and WAGRO syndromes (WAGR and obesity). Furthermore, recent research shows that aniridia associated with alterations in the PAX6 gene often shows further systemic implications (e.g. endocrine, metabolic and neurological pathologies). Therefore, PAX6-related aniridia is more and more considered to be and described as aniridia syndrome or PAX6 syndrome. We present a group of 130 patients with congenital aniridia to enhance awareness of the complexity of the disease. Different to other congenital visual impairments aniridia is characterized by many ocular complications arising during the lifetime which may lead to total blindness (e.g. cataract, aniridic keratopathy and secondary glaucoma). Furthermore, there is a specific surgical risk entity: aniridia fibrosis syndrome and anterior segment fibrosis syndrome (ASFS) which lead to a non-infectious fibrous scarring and membrane formation of the anterior segment, often followed by hypotonia and phthisis. Aniridic glaucoma presents yet another severe complication which is often diagnosed late due to diagnostic problems and which may lead to irreversible optic nerve damage. The following approaches might help to improve the lifelong care of aniridia patients and might benefit the aim to lessen the impact of complications in aniridia: topical prophylaxis of aniridic corneal epitheliopathy from a very early age, regular measurement of intraocular pressure starting in young children, annual visual evoked potential (VEP) measurements and routine visual field testing as soon as possible, comprehensive optimization of surgical care independent of department location (only the very best surgeons within their subspecialty should treat the different complications) while one experienced pediatric and low vision ophthalmologist should follow the patient continuously ("aniridia guide" for the patient), thus monitoring the disease and stages of complications and advising the patient where to go for surgical treatment. This low vision ophthalmologist continuously follows the patient's course including adaptation of low vision aids according to the course of the disease, helping the patient concerning integration at school and at the place of work and advising about social and legal compensation possibilities. In addition, the guiding ophthalmologist should inform patients with aniridia about possible systemic manifestations of PAX6 syndrome concerning metabolic and neurological implications and should initiate appropriate investigations when applicable.
    Der Ophthalmologe 12/2014; 111(12). DOI:10.1007/s00347-014-3060-x · 0.72 Impact Factor
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    ABSTRACT: Background/Aims: Excess maternal salt intake during pregnancy may alter fetal development. However, our knowledge on how an increased salt intake during pregnancy influences fetal eye development is limited. In this study, we investigated the effects of high-salt treatment on the developing eyes in chick embryos, especially focusing on the development of the retina and the lens. Methods: 5.5-day chick embryos were exposed to 280mosm/l (n=17), or 300mosm/l (n=16) NaCl. The treated embryos were then incubated for 96 hours before they were fixed with 4% paraformaldehyde for H&E staining, whole-mount embryo immunostaining and TUNEL staining. BrdU and PH3 incorporation experiments were performed on the chick embryos after high-salt treatment. RT-PCR analyses were conducted from chick retina tissues. Results: We demonstrated that high-salt treatment altered the size of eyes in chick embryos, induced malformation of the eyes and impaired the development of the lens and the retina. We found an impaired expression of Paired box 6 (PAX6) and neuronal cells in the developing retina as revealed by neurofilament immunofluorescent staining. There was a reduction in the number of BrdU-positive cells and PH3-positive cells in the retina, indicating an impaired cell proliferation with high-salt treatment. High-salt treatment also resulted in an increased number of TUNEL-positive cells in the retina, indicating a higher amount of cell death. RT-PCR data displayed that the expression of the pro-apoptotic molecule nerve growth factor (NGF) in chick retina was increased and CyclinD1 was reduced with high-salt treatment. The size of the lens was reduced and Pax6 expression in the lens was significantly inhibited. High salt-treatment was detrimental to the migration of neural crest cells. Conclusion: Taken together, our study demonstrated that high-salt exposure of 5.5-day chick embryos led to an impairment of retina and lens development, possibly through interfering with Pax6 expression. © 2014 S. Karger AG, Basel.
    Cellular Physiology and Biochemistry 08/2014; 34(3):804-817. DOI:10.1159/000363044 · 3.55 Impact Factor


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Oct 14, 2014