A novel missense RP1 mutation in retinitis pigmentosa

More than 20 mutations associated with retinitis pigmentosa (RP) have been identified in the retinitis pigmentosa 1 (RP1) gene, all of them leading to the production of a truncated protein without 50-70% of the C-terminal of the RP1 protein. RP1 was recently found to be a microtubule-associated protein (MAP) and responsible for the organisation of the photoreceptor outer segment. The N-terminal doublecortin (DCX) domain of RP1 is essential for its function. But how the C-terminal of the protein affects its function is still not known. This study aims to get a better understanding of the RP1 gene by mutation screening on RP patients.

Peripheral blood was taken from 72 RP patients. Together with 101 RP patients and 190 control subjects previously reported, mutation screening was performed by polymerase chain reaction (PCR) and direct sequencing. Statistical analysis was performed using SPSS.

Two novel missense sequence changes, D984G and C727W, and one novel variant, 6492T>G, at the 3' untranslated region were found. They were not found in 190 control subjects. D984G causes RP. It creates two possible N-myristoylation sites according to PROSITE. C727W does not segregate with RP in the family. It abolishes an N-myristoylation site. R872H, a previously reported polymorphism, was predominantly present in control subjects (P=0.001).

Our results suggest that disruption of the C-terminal of RP1 may be associated with the development of RP, and the possible involvement of the RP1 polypeptide downstream of its DCX domain in normal RP1 function.