['Heterozygous mutations in the GUCY2D gene, which encodes the membrane-bound retinal guanylyl cyclase-1 protein (RetGC-1), have been shown to cause autosomal dominant inherited cone degeneration and cone-rod degeneration (adCD, adCRD). The present study was a comprehensive screening of the GUCY2D gene in 27 adCD and adCRD unrelated families of these rare disorders.', 'Mutation analysis was performed by direct sequencing as well as PCR and subsequent restriction length polymorphism analysis (PCR/RFLP). Haplotype analysis was performed in selected patients by using microsatellite markers.', 'GUCY2D gene mutations were identified in 11 (40%) of 27 patients, and all mutations clustered to codon 838, including two known and one novel missense mutation: p.R838C, p.R838H, and p.R838G. Haplotype analysis showed that among the studied patients only two of the six analyzed p.R838C mutation carriers shared a common haplotype and that none of the p.R838H mutation carriers did.'] Does mutation analysis identify GUCY2D as the major gene responsible for autosomal dominant progressive cone degeneration?