Screening of the RP2 and RP3 Genes in Sporadic Cases of Retinitis Pigmentosa (RP) in Ambiguous X-Linked RP Families With Unexpected Recombination Events in Infants and in False Autosomal Dominant RP Families: Improvement of Genetic Counselling

Abstract

Abstract: : Purpose: To improve genetic counselling in 41 RP families in whom genetic traps were met, by screening the two major X-linked RP genes: RP2 and RP3. Methods: One affected patient of each of the 41 families were screened for mutation using direct sequencing. Results: It is admitted that the RP3 gene is involved in at least 70% of X-linked retinitis pigmentosa. It is why we first screened this gene.Uptill now, this screening already allowed to solve ambiguities met in 18/41 families: 5 families in whom RP2 and RP3 could not be distinguished by linkage analyses, 8 families suspected to be autosomal dominant without father to son transmission, in 3 families with unexpected recombination event between RP2 and RP3 identified in children to young to have a definite status or in potential carriers, in 1 family with a false paternity preventing from ruling on the status of a potential carrier female and finally and in 1 sporadic male affected with a phenotype compatible with X-linked RP. The screening of the RP2 gene is still in process. Conclusions: This study shows that the identification of RP2 or RP3 mutations is crucial in some unusual situations, highlighting the limits of the indirect studies in some families.

Keywords: genetics • retinal degenerations: hereditary