Transcriptional expression of cis-acting and trans-acting splicing mutations cause autosomal dominant retinitis pigmentosa.

Two types of mutations may lead to deficient pre-mRNA splicing: cis-acting mutations that inactivate a constitutive or alternative splice site within the pre-mRNA, and trans-acting mutations that affect the function of a basal factor of the splicing machinery. Autosomal dominant retinitis pigmentosa (adRP) is caused by mutations in at least 12 genes, with mutations in rhodopsin being the most prevalent. Two cis-acting mutations, g.3811A>G and g.5167G>T at the splice site in the rhodopsin gene (RHO; GenBank U49742.1) are linked to adRP in a Spanish population; while a cis-acting mutation, g.4335G>T, has been linked to recessive RP (arRP). Transcriptional expression analysis showed that the cis-acting splicing mutations linked to adRP promoted alternative splice sites, while the arRP linked mutation results in exclusion of exon 4. Trans-acting splicing mutations associated with adRP have also been found, and mutations in the pre-mRNA splicing factors PRPF3, PRPF8, PRPF31, and RP9 are associated with adRP in several populations. This report describes a new mutation in PRPF3 in a Spanish adRP family. We also investigated the transcriptional patterns in Epstein-Barr virus (EBV)-transformed lymphoblastoid cells from patients carrying a mutation in PRPF8. Despite the role of PRPF8 in the minor U12 splicing processes, microarray analysis revealed that mutations in PRPF8 not only did not result in significant differences in splicing efficiency of rhodopsin, but no apparent changes in expression of U12-type intron genes and splicing processes was observed. Microarray analysis revealed a panel of differentially expressed genes mapped to the RP loci, and future work will determine their role in RP.

High prevalence of mutations in peripherin/RDS in autosomal dominant macular dystrophies in a Spanish population.

PURPOSE: Mutations in the peripherin/retinal degeneration slow (RDS) gene are a known cause of various types of central retinal dystrophies. The purpose of this study was to determine the prevalence of mutations in the peripherin/RDS gene in Spanish patients with different types of autosomal dominant macular dystrophy. METHODS: Ophthalmic and electrophysiological examination was performed in patients from 61 unrelated autosomal dominant macular dystrophy (adMD) Spanish families. Screening for mutations in the peripherin/RDS gene by denaturing gradient gel electrophoresis (DGGE) and direct genomic sequencing was performed in index patients and extended to the family when positive. RESULTS: We report four novel mutations in peripherin/RDS and a relatively high frequency (23%) of mutations in this gene in families with adMD. Thirteen different mutations were found in fifteen adMD families. Three novel missense, four nonsense and a cis-acting splicing mutation IVS2+2T>C, were found in a Spanish population while five more missense mutations were also reported in other populations. The Arg142Trp and Arg172Trp mutations, present in several populations, were both detected in two independent Spanish families. All the missense mutations produce an amino acid substitution in the second intradiscal loop of the peripherin, while the nonsense mutations presumably generate a truncated protein. CONCLUSIONS: A high frequency (23%) of mutations in the peripherin/RDS gene was found in a cohort of 61 unrelated patients with various types of autosomal dominant central retinal dystrophies as compared with a low prevalence (1.3%) of mutations in this gene causing retinitis pigmentosa in a Spanish population. Different macular dystrophy phenotypes according to the mutations in peripherin/RDS are shown. However, a limited phenotype variation was observed for these mutations within the family.