RPE65 gene mutations represented a significant cause of LCA in the Italian population, whereas GUCY2D and CEP290 mutations had a lower frequency than that found in other reports. This finding suggests that the genetic epidemiology of LCA in Italy is different from that reported in the United States and in northern European countries. Autofluorescence in patients with RPE65 mutations was more frequently associated with preserved retinal thickness, which suggests that these mutations are not associated with progression of retinal degeneration. Therefore, normal retinal thickness (identified with OCT) and fundus autofluorescence may be the means with which to identify patients with LCA who carry RPE65 mutations, which are expected to be a potential gene therapy target in the near future.

Choroideremia (CHM), an X-linked degeneration of the retinal pigmented epithelium (RPE), photoreceptors, and choroid, ultimately leads to blindness. It is caused by loss-of-function of the CHM gene product, the Rab escort protein 1 (REP1) that is involved, together with its homologue REP2, in prenylation of Rab GTPases, key regulators of intracellular vesicular traffic. Here, we report the molecular characterization of 20 unrelated Italian families affected by CHM. We identified 19 different mutations, nine of which are new. In most cases, we analyzed the effect of the mutations at the mRNA level. Furthermore, we demonstrated, by in vitro trancription/translation assays, that the mutated mRNAs produced truncated proteins in all cases but one. In fact, we also identified a novel REP1 missense variant (c.1520A>G; p.H507R) associated to CHM. Thus far, only two other CHM-associated missense mutations have been identified, one of which was a splicing alteration. We investigated the impact of the p.H507R amino acid change on REP1 structure and function, thus providing the first experimental demonstration that correlates a missense mutation in CHM with a functional impairment of REP1. Overall, our results indicate that the REP1-Rab geranyl-geranyl transferase interaction and consequently REP1-mediated Rab prenylation is essential for RPE and photoreceptor function.

Retinitis pigmentosa is the most common form of retinal degeneration and is heterogeneous both clinically and genetically. The autosomal dominant forms (ADRP) can be caused by mutations in 12 different genes. This report describes the first simultaneous mutation analysis of all the known ADRP genes in the same population, represented by 43 Italian families. This analysis allowed the identification of causative mutations in 12 of the families (28% of the total). Seven different mutations were identified, two of which are novel (458delC and 6901CRT (P2301S), in the CRX and PRPF8 genes, respectively). Several novel polymorphisms leading to amino acid changes in the FSCN2, NRL, IMPDH1, and RP1 genes were also identified. Analysis of gene prevalences indicates that the relative involvement of the RHO and the RDS genes in the pathogenesis of ADRP is less in Italy than in US and UK populations. As causative mutations were not found in over 70% of the families analysed, this study suggests the presence of further novel genes or sequence elements involved in the pathogenesis of ADRP. R etinitis pigmentosa is a clinically and genetically heterogeneous type of retinal degeneration which results in progressive loss of vision. It is characterised by abnormalities of the photoreceptors or the retinal pigment epithelium. Patients with this disorder typically develop night blindness, followed by constriction of the peripheral visual fields, bone spicule-like pigmentary deposits, and abnormal electroretinography (ERG). In the more advanced stages of the disease, there are intraretinal and preretinal clumps of black melanin pigment, attenuated retinal vessels, loss of retinal pigment epithelium, and pallor of the optic nerve.1 The time of onset of the disease varies from childhood to middle age.2 The incidence is estimated to be 1 in 4000-5000 people in Western populations.3 4 Inheritance can be autosomal dominant, autosomal recessive, X linked, or in rare cases as a digenic trait. However, in the majority of cases (about 50-60% in the white population) it is impossible to establish the pattern of inheritance, and these cases are defined as ''sporadic. '' 5-7 Autosomal dominant retinitis pigmentosa (ADRP) represents between 15% and 35% of all cases of the disorder, depending on the countries and the ethnic groups analysed, with the highest values being found in the USA 8 and the lowest in southern Europe.9 A previous study reported that the prevalence of ADRP in the Italian population is about 17%, 10 which is concordant with estimates from other studies carried out in southern Europe. 9 To date, 12 genes have been clearly associated with the pathogenesis of this condition (RETnet, http://www.sph.uth.tmc.edu/Retnet/disease.htm). The rhodopsin (RHO) gene is the most commonly involved in ADRP (25-50% of cases) followed by RP1 (5-10%), RDS (5%), and IMPDH1 (5-10%). These prevalence values were all derived from different and heterogeneous studies mostly carried out in American and British populations, 6 11 12 and a simultaneous ...

Autosomal recessive Stargardt disease (STGD) has been associated with substantial genetic and phenotypic heterogeneity. By systematic clinical analyses of STGD patients with complete genetic data (i.e. identified mutations on both alleles of the ABCA4 gene), we set out to determine phenotypic subtypes and to correlate these with specific ABCA4 alleles. Twenty-eight patients from 18 families with STGD/fundus flavimaculatus were investigated. All patients were submitted to complete ophthalmologic examination, electrophysiology, fluorescein angiography and ABCA4 gene chip analysis. Two main clinical phenotypes were observed among the examined patients. The severe phenotype was characterized by the onset of the disease <20 years and reduced ERG response, whereas the mild phenotype presented with later onset of the disease and a normal ERG response. Genetic analysis of the ABCA4 gene revealed, in the severe group, more frequently deletions, stop codons and insertions as compared to the mild phenotype group (p = 0.0113 by Fisher’s exact test). Moreover, the compound heterozygous mutations G1961E/5018 + 2T → C found in 7 patients from 3 unrelated STGD families were associated with a mild phenotype in all subjects, except 1. This study documented variability of the clinical expression of STGD in relation to the age of onset of the disease, fundus appearance and the ERG response and allowed to subdivide patients into a severe and a mild phenotype group. These findings suggest that an extensive and comprehensive genetic analysis of STGD patients combined with thorough clinical evaluation, including the careful recording of the age of onset of the disease, would allow a more precise prognostic evaluation.