Purpose: The purpose of this study was to investigate the disease-causing mutations for retinitis pigmentosa (RP) patients and function of mutations.
Methods: We recruited RP families and sporadic RP patients, and performed whole-exome sequencing (WES) to screen for sequence variations. Subsequently, we investigated the expression of green fluorescent protein (GFP) merged expression vectors containing PRPF31 wild type (WT) and its variants. We determined protein stability by cycloheximide (CHX) treatment.
Results: Two frameshift variants, c.547delG (p.E183fs) and c.804delG (p.L268fs), and one stopgain variant, c.1060C>T (p.R354X), in the pre-mRNA processing factor 31 gene (PRPF31) were identified in three RP families. In comparison with WT, the expressions of GFP-fused PRPF31 (GFP-PRPF31) protein with the mutation c.547delG or c.804delG in HEK293 cells were significantly reduced. However, the expression of GFP-PRPF31 containing the stopgain mutation (GFP-PRPF31sg) was increased. CHX treatment of HEK293 showed the GFP-PRPF31sg protein was more stable than GFP-PRPF31 WT. The WT protein expression was localized in the nuclei, and the mutants in both nuclei and cytoplasm. We screened for PRPF31 mutations in 131 sporadic RP patients by WES and successfully identified three novel mutations: c.G781C (p.G261R), c.A1373T (p.Q458L), and c.C1222T (p.R408W).
Conclusions: Our study revealed novel mutations of PRPF31 in RP. Our results also showed that the two mutations (c.547delG or c.804delG) affect gene expression and GFP-PRPF31sg has increased protein stability.