CHAPTER 2 DISEASE-ASSOCIATED VARIANTS OF THE ROD- DERIVED CONE VIABILITY FACTOR (RdCVF) IN LEBER CONGENITAL AMAUROSIS Rod-derived cone viability variants in LCA Sylvain Hanein 1 , Isabelle Perrault 1 , Sylvie Gerber 1 , Hélène Dollfus 2 , Jean-Louis Dufier 3 , Josué Feingold 1 , Arnold Munnich 1 , Shomi Bhattacharya 4 , Josseline Kaplan 1 , José-Alain Sahel 5 , Jean-Michel Rozet 1 , and Thierry Leveillard 5 1. INTRODUCTION Leber congenital amaurosis (LCA) is the most early and severe form of all inherited retinal dystrophies, responsible for congenital blindness. The genetic heterogeneity of LCA has been accepted for a long time but it turned out to be largely higher than all odds. So far, 11genes have been mapped on human chromosomes and eight identified. i) the retinal specific guanylate cyclase gene (GUCY2D, retGC1; 17p13.1; LCA1; MIM 600179), ii) the gene encoding the 65-kD protein specific to the retinal pigment epithelium (RPE65; 1p31; LCA2; MIM180069), iii) the cone-rod homeobox-containing gene (CRX; 19q13.3; LCA7; MIM 60225), iv) the gene encoding the arylhydrocarbon receptor interacting protein-like 1 (AIPL1; 17p13.1; LCA; MIM 604392), v) the gene encoding the retinitis pigmentosa GTPase regulator-interacting protein 1 (RPGRIP1; 14q11; LCA6; MIM 605446), vi) the human homologue of the drosophila melanogater crumbs gene (CRB1; 1q31; LCA8; MIM 604210), vii) the gene encoding the tubby-like protein 1 (TULP1; 6q21.3; LCA10; MIM 602280), viii) the retinol dehydrogenase 12 (RDH12; 14q24; LCA11; MIM 608830), ix) LCA3 (14q24; MIM 604232), x) LCA5 (6q11-16; MIM 604537) and xi) LCA9 (1p36; MIM608553). 9 1 Unité de Recherches sur les Handicaps Génétiques de l’Enfant. Hôpital Necker - Enfants Malades, 149 rue de Sèvres, 75743 Paris Cedex 15, France. Email: kaplan@necker.fr; 2 Clinique Ophtalmologique, Hopitaux Universitaires de Strasbourg, Strasbourg, France; Service d’ophtalmologie, Hôpital Necker, France; 4 Departments of Molecular Genetics and Visual Science, Institute of Ophthalmology, London, United Kingdom. Moorfields Eye Hospital, London, United Kingdom; 5 Laboratoire de physiopathologie cellulaire et moléculaire de la rétine Inserm U592, Paris, France.