Cloning and gene structure of the rod cGMP phosphodiesterase delta subunit gene (PDED) in man and mouse

Rod-specific cGMP phosphodiesterase (PDE) is a key enzyme of the phototransduction cascade, and mutations in its catalytic subunits have been associated with retinal degenerative diseases, The bovine Q-subunit solubilises the normally membrane-bound PDE and is the only subunit expressed in extraocular tissues, We isolated the human and mouse orthologs, and found 78% identity at the DNA level and 98% identity at the protein level, The Caenorhabditis elegans homolog shows 69% identity at the protein level, The human PDED gene consisted of 5 exons spanning at least 30 kb of genomic DNA, Northern blot analysis showed a 1,3 kb transcript in human retina, heart, brain, placenta, liver, and skeletal muscle, Fluorescence in situ hybridisation (FISH) and radiation hybrid mapping localised the human PDED gene to chromosome 2q37, A preliminary screen of all 5 exons in 20 unrelated patients with autosomal recessive retinitis pigmentosa revealed no PDED mutations.