Journal article

Publication year: 2008

Pages: 5235-5242

Journal: Investigative ophthalmology & visual science

Volume number: 49

Issue number: 12

ISSN: 0146-0404

eISSN: 1552-5783

Open access status: Green

DOI Link: https://doi.org/10.1167/iovs.07-1671

Publisher: Association for Research in Vision and Ophthalmology

Abstract: 

PURPOSE. Later onset and progression of retinal dystrophy occur with some RPE65 missense mutations. The functional consequences of the novel P25L RPE65 mutation was correlated with its early-childhood phenotype and compared with other pathogenic missense mutations.

METHODS. In addition to typical clinical tests, fundus autofluorescence (FAF), optical coherence tomography (OCT), and two-color threshold perimetry (2CTP) were measured. RPE65 mutations were screened by SSCP and direct sequencing. Isomerase activity of mutant RPE65 was assayed in 293F cells and quantified by HPLC analysis of retinoids.

RESULTS. A very mild phenotype was detected in a now 7-year-old boy homozygous for the P25L mutation in RPE65. Although abnormal dark adaptation was noticed early, best corrected visual acuity was 20/20 at age 5 years and 20/30 at age 7 years. Nystagmus was absent. Cone electroretinogram (ERG) was measurable, rod ERG severely reduced, and FAF very low. 2CTP detected mainly cone-mediated responses in scotopic conditions, and light-adapted cone responses were approximately 1.5 log units below normal. High-resolution spectral domain OCT revealed morphologic changes. Isomerase activity in 293F cells transfected with RPE65/P25L was reduced to 7.7% of wild-type RPE65-transfected cells, whereas RPE65/ L22P-transfected cells had 13.5%.

CONCLUSIONS. The mild clinical phenotype observed is consistent with the residual activity of a severely hypomorphic mutant RPE65. Reduction to <10% of wild-type RPE65 activity by homozygous P25L correlates with almost complete rod function loss and cone amplitude reduction. Functional survival of cones is possible in patients with residual RPE65 isomerase activity. This patient should profit most from gene therapy. (Invest Ophthalmol Vis Sci. 2008; 49: 5235-5242) DOI: 10.1167/iovs.07-1671

Harvard Citation style: Lorenz, B., Poliakov, E., Schambeck, M., Friedburg, C., Preising, M. and Redmond, T. (2008) A Comprehensive Clinical and Biochemical Functional Study of a Novel RPE65 Hypomorphic Mutation, Investigative ophthalmology & visual science, 49(12), pp. 5235-5242. https://doi.org/10.1167/iovs.07-1671

APA Citation style: Lorenz, B., Poliakov, E., Schambeck, M., Friedburg, C., Preising, M., & Redmond, T. (2008). A Comprehensive Clinical and Biochemical Functional Study of a Novel RPE65 Hypomorphic Mutation. Investigative ophthalmology & visual science. 49(12), 5235-5242. https://doi.org/10.1167/iovs.07-1671