Evaluation of retinal photoreceptors and pigment epithelium in a female carrier of choroideremia

Gene Therapy for Choroideremia Using an Adeno-Associated Viral (AAV) Vector

“…For reasons that are not completely clear, cones are known to be dependent on surrounding rods, and any genetic condition that causes rod death will also lead to complete loss of cones in a centripetal pattern as a secondary phenomenon. In a postmortem analysis of the retina from an X-linked carrier female, apparently normal-looking, REP1-deficient cones could be identified within regions containing REP1 expressing rods (Syed et al 2001). The differential expression of REP1 in these two photoreceptor subclasses results from differential X-inactivation (Reese et al 1995) and provides further evidence that cones may exist without REP1 when surrounded by rods.…”

“…Fortunately, human data and observations exist that are more illuminating. Studies from postmortem carrier females show no focal loss or abnormalities of the choroid except underlying areas of severe retinal degeneration (Syed et al 2001), which suggests that the choroidal vascular system is not dependent on REP1. Similarly, choroideremia is not known to affect blood vessels elsewhere in the body.…”

“…In human female carriers, skewed X-inactivation across the retinal layers can leave affected clones of photoreceptors against normal pigment epithelial cells, and histological postmortem specimens suggest that photoreceptors degenerate independently of the RPE (Flannery et al 1990;Syed et al 2001;Bonilha et al 2008). There is also evidence from optical coherence tomography scans of male choroideremia patients that the photoreceptor layer thins in advance of degeneration of the RPE (Jacobson et al 2006b).…”

Vi-2 : Apport De l'ÉLECTROPHYSIOLOGIE Chez l'ADULTE : Exemples

“…Tardivement, elles peuvent se plaindre de difficulté à l'obscurité, probablement en lien avec la dégénérescence localisée de bâtonnets qui sont plus spécifiquement touchés que les cônes par les mutations du gène de la choroïdérémie [Syed et al, 2001]. La fonction rétinienne de la majorité d'entre elles est normale [Miyake, 2006] ; seules quelque unes présentent des modifications de leur ERG flash [Sieving, et al, 1986].…”

Electroretinogram in Hereditary Retinal Disorders

“…The retinas of female carriers are mosaics, containing patches of both mutant and normal cells. As a result of mosaicism, female carriers usually show patchy depigmentation of the retinal pigment epithelium, but can retain good visual function throughout life (Syed et al, 2001). In the early stages of the disease, both a-and b-wave amplitudes are reduced and the implicit times delayed ).…”