MOLECULAR STUDY OF THE RHODOPSIN GENE IN RETINITIS-PIGMENTOSA PATIENTS IN THE BASQUE COUNTRY

Retinitis pigmentosa (RP) is a degenerative disorder affecting the out er segment of the retina and leading to night blindness and progressiv e visual field loss. The rhodopsin gene encodes a photolabile pigment located in the rod outer segments constituting around 80-90% of its pr otein content and is the initiation point for the visual cascade upon absorption of a single photon. Seventy-five unrelated, isolated RP fam ilies in the Basque Country, with at least one affected member, were d iagnosed at our hospital after ophthalmic examination and electroretin ogram analysis. The patients received genetic counselling according to their individual case based on their clinical diagnosis. The modes of inheritance found from pedigree studies were the following: 20% (15/7 5) were classified as autosomal dominant retinitis pigmentosa (ADRP), 17.33% (13/75) were autosomal recessive (ARRP), 2.66% (2/75) were uncl assified (NC), and 60% (45/75) were sporadic cases (SCRP). From these families, 75 unrelated and affected index cases together with 22 affec ted relatives and 42 unaffected relatives were screened for mutations in the rhodopsin gene by GC clamped denaturing gradient gel electropho resis. Our results showed that five ADRP, three ARRP, 15 SCRP, and one NC families had alterations in this gene. Only three of these alterat ions, that is 4% (3/75) (95% CL 0-8), appeared to be responsible for t he disease. This represents a lower percentage than the 10% previously reported.