Structure and Function in Rhodopsin. 7. Point Mutations Associated with Autosomal Dominant Retinitis Pigmentosa

Abstract

Autosomal dominant retinitis pigmentosa (ADRP) is a hereditary form of retinitis pigmentosa which accounts for about 15% of all types of the latter disease. Recently, close to 50 mutations, mostly point mutations, have been identified in the rhodopsin gene in ADRP patients. We have introduced these mutations in the synthetic bovine rhodopsin gene and herein report on the expression of the mutant genes in COS-1 cells and studies in vitro of the properties of the expressed opsins. The mutant phenotypes fall into three classes: Class I mutants are expressed in COS-1 cells at wild-type levels, form the normal rhodopsin chromophore with 11-cis-retinal, and are transported to the cell surface. However, on illumination, they activate transducin inefficiently. Class II mutants remain in the endoplasmic reticulum and do not bind 11-cis-retinal to form the chromophore. Class III mutants are expressed at low levels and form rhodopsin chromophore only poorly. They also remain in the endoplasmic reticulum and, as expected, show high mannose glycosylation. Nearly all of the mutants studied show abnormal sensitivity to light compared to the wild type, and they activate transducin less efficiently. We conclude that the majority of the ADRP mutants have folding defects.

Next-generation sequencing in health-care delivery: lessons from the functional analysis of rhodopsin

“…Similar to F45L, this variant was identified in a previous study 17 and thought to be pathogenic; 12,18 however, it has recently been recategorized as an "unclassified" mutation because of the lack of valid functional information. 10 Residue 53 is located in the first TMD of the rhodopsin protein structure (Figure 2a and Supplementary Figure S3 online).…”

“…We also included two positive controls: P23H, the most common pathogenic mutation in rhodopsin, 4,9,10 where there is clear evidence of pathogenicity using in vitro expression systems and immunocytochemistry, [11][12][13][14][15] and ∆68-71, which spans one of our variants and has been demonstrated to be functionally inactive. [16][17][18] spectrophotometry WT and variant constructs were transiently transfected into human embryonic kidney cells (Supplementary Materials and Methods online).…”

Traffic Jams II: An Update of Diseases of Intracellular Transport

“…Autosomal dominant Rhodopsin Blindness In some common mutations of rhodopsin leading retinitis pigmentosa to ADRP the rhodopsin protein is incorrectly folded, (ADRP) leading to its aggregation and retention in the (19)(20)(21) Golgi and ER.…”

Hereditary Degenerative Retinopathies: Optimism for Somatic Gene Therapy

“…To characterize the biochemical defects associated with rhodopsin mutations, a tissue culture expression system has been used. On the basis of this type of transfection experiments (6)(7)(8), it has been proposed that normal cell functions are disrupted because of an abnormal proteinfolding or misrouting of the mutant rhodopsin. However, these changes are not speci c for a particular mutation, and it is difcult to explain how mutations in a single gene can produce several different phenotypes.…”