ABSTRACT
Retinal dystrophies constitute a group of clinically and genetically heterogeneous diseases that cause visual impairment. As treatments are not readily available, readout assays performed in patient-derived cells can aid in the development and comparative analysis of therapeutic approaches. We describe a new method with which the localization of the retinitis pigmentosa GTPase regulator (RPGR) protein along the cilium can be used as a measure for treatment efficacy. In a patient-derived fibroblast cell line, we found that the RPGR protein is mislocalized along the ciliary axoneme. The patient carried a point mutation that leads to skipping of RPGR exon 10. We confirmed that this skipping is causative for the impaired localization of RPGR using a U7 small nuclear RNA (U7snRNA)-based antisense approach in control cells. Treatment of the patient-derived fibroblasts with therapeutic U1snRNA significantly corrected the proteins' mislocalization. In this proof of principle study, we show that detecting the RPGR protein along the cilium provides a reliable and quantifiable readout assay to evaluate the efficacy of therapies intended to correct or silence RPGR gene mutations. This method opens the possibility to compare different therapeutic agents, and thus facilitate the identification of treatment options for the clinically and molecularly complex RPGR-associated diseases.
Subject(s)
Eye Proteins/genetics , Point Mutation , RNAi Therapeutics/methods , Retinal Dystrophies/genetics , Amino Acid Sequence , Animals , Cell Line , Cilia/genetics , Cilia/metabolism , Exons , Eye Proteins/chemistry , Eye Proteins/metabolism , Fibroblasts/metabolism , Humans , Mice , Molecular Sequence Data , Protein Transport , RNA, Small Nuclear/genetics , Retinal Dystrophies/metabolism , Retinal Dystrophies/therapyABSTRACT
BACKGROUND: IL-18 is a pleiotrophic cytokine involved in both, T-helper type 1 (Th1) and Th2 differentiation. Recently genetic variants in the IL-18 gene have been associated with increased risk of atopy and asthma. OBJECTIVE: To examine the relationship of a genetic, haplotype-tagging promotor variant -137G/C in the IL-18 gene with atopic asthma in a large, well-characterized and population-based study of adults. METHODS: Prospective cohort study design was used to collect interview and biological measurement data at two examination time-points 11 years apart. Multivariate logistic regression analysis was used to assess the association of genotype with asthma and atopy. RESULTS: The G-allele of the IL-18 promotor variant (-137G/C) was associated with a markedly increased risk for the prevalence of physician-diagnosed asthma with concomitant skin reactivity to common allergens. Stratification of the asthma cases by skin reactivity to common allergens revealed an exclusive association of IL-18 -137 G-allele with an increased prevalence of atopic asthma (adjusted odds ratio (OR): 3.63; 95% confidence interval: (1.64-8.02) for GC or GG carriers vs. CC carriers), and no according association with asthma and concomitant negative skin reactivity (adjusted OR: 1.13; 0.66-1.94). The interaction between IL-18 -137G/C genotype and positive skin prick test was statistically significant (P=0.029). None of 74 incident asthma cases with atopy at baseline exhibited the CC genotype. CONCLUSION: Our results strongly suggest that this variant of the IL-18 gene is an important genetic determinant involved in the development of atopic asthma.
