The general strategies of phototransduction in vertebrates and invertebrates share many similarities, but differ significantly in their underlying molecular machinery. The CDS gene encodes the CDP-diacylglycerol synthase (CDS) enzyme and is required for phototransduction in Drosophila. Using a bioinformatic approach, we have identified two novel transcripts (CDS1 and CDS2) highly homologous to the Drosophila CDS gene. We isolated and sequenced the CDS2 full-length cDNA and mapped the two genes to human chromosomes 20p13 (CDS2) and 4q21.1 (CDS1). Sequence analysis revealed that both genes are highly homologous to the Drosophila protein (64.4 and 58.6% identity at the protein level between CDS and CDS2 and between CDS and CDS1, respectively). The mouse homologs for both genes were isolated and used in RNA in situ hybridization studies on adult and embryonic mouse tissue sections. These studies showed that Cds2 is highly expressed in the differentiating neuroblasts of the neural retina and in the central nervous system during embryonic development, while it was not detected in adult retina. Cds1, on the other hand, shows a high level of expression in the photoreceptor layer of adult retina, which strongly suggests a role for Cds1 in phototransduction. Knowledge of the expression pattern of these genes in mammals may shed light on the evolution of vision mechanisms and help in the evaluation of candidate genes for human retinopathies.
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