Disruption of the 11-cis-retinol dehydrogenase gene leads to accumulation of cis-retinols and cis-retinyl esters.

To elucidate the possible role of 11-cis-retinol dehydrogenase in the visual cycle and/or 9-cis-retinoic acid biosynthesis, we generated mice carrying a targeted disruption of the 11-cis-retinol dehydrogenase gene. Homozygous 11-cis-retinol dehydrogenase mutants developed normally, including their retinas. There was no appreciable loss of photoreceptors. Recently, mutations in the 11-cis-retinol dehydrogenase gene in humans have been associated with fundus albipunctatus. In 11-cis-retinol dehydrogenase knockout mice, the appearance of the fundus was normal and punctata typical of this human hereditary ocular disease were not present. A second typical symptom associated with this disease is delayed dark adaptation. Homozygous 11-cis-retinol dehydrogenase mutants showed normal rod and cone responses. 11-cis-Retinol dehydrogenase knockout mice were capable of dark adaptation. At bleaching levels under which patients suffering from fundus albipunctatus could be detected unequivocally, 11-cis-retinol dehydrogenase knockout animals displayed normal dark adaptation kinetics. However, at high bleaching levels, delayed dark adaptation in 11-cis-retinol dehydrogenase knockout mice was noticed. Reduced 11-cis-retinol oxidation capacity resulted in 11-cis-retinol/13-cis-retinol and 11-cis-retinyl/13-cis-retinyl ester accumulation. Compared with wild-type mice, a large increase in the 11-cis-retinyl ester concentration was noticed in 11-cis-retinol dehydrogenase knockout mice. In the murine retinal pigment epithelium, there has to be an additional mechanism for the biosynthesis of 11-cis-retinal which partially compensates for the loss of the 11-cis-retinol dehydrogenase activity. 11-cis-Retinyl ester formation is an important part of this adaptation process. Functional consequences of the loss of 11-cis-retinol dehydrogenase activity illustrate important differences in the compensation mechanisms between mice and humans. We furthermore demonstrate that upon 11-cis-retinol accumulation, the 13-cis-retinol concentration also increases. This retinoid is inapplicable to the visual processes, and we therefore speculate that it could be an important catabolic metabolite and its biosynthesis could be part of a process involved in regulating 11-cis-retinol concentrations within the retinal pigment epithelium of 11-cis-retinol dehydrogenase knockout mice.

Cloning and structural analysis of the murine GCN5L1 gene.

We recently cloned the murine 11-cis retinol dehydrogenase gene. A second gene, the murine GCN5L1 gene, was found to be situated upstream of the murine 11-cis retinol dehydrogenase gene. We have isolated and sequenced the complete coding sequence of the murine GCN5L1 gene. The distance between the 3'-end of the murine GCN5L1 gene and the 5'-end of the 11-cis retinol dehydrogenase gene is only 776 nt. The murine GCNSL1 gene consists of four exons encompassing approximately 3.5 kb of genomic DNA. Intron/exon splice sites conform to the GT/AG rule. The open reading frame consists of 375 nucleotides encoding a 14 kDa protein. The murine GCN5L1, like the human GCN5L1 protein, displays weak homology (27%) to yeast GCN5. The distance between the murine, human and bovine GCN5L1 and 11-cis retinol dehydrogenase genes appeared to be conserved.

Null mutation in the human 11-cis retinol dehydrogenase gene associated with fundus albipunctatus.

PURPOSE: Recent studies show that mutations in the gene encoding 11-cis retinol dehydrogenase are associated with fundus albipunctatus. The authors wanted to investigate whether additional, more severe, mutations in the 11-cis retinol dehydrogenase gene might be responsible for more severe forms of hereditary retinal diseases. DESIGN: Case-control molecular genetics study. PARTICIPANTS AND CONTROLS: Two index patients, 7 relatives, and 50 control individuals. METHODS: The authors screened two index patients diagnosed with fundus albipunctatus for mutations in exons 2 to 5 and exon/intron boundaries of the 11-cis retinol dehydrogenase gene by direct sequencing. Control individuals were screened for the presence of the mutations using allele-specific oligonucleotide hybridization. MAIN OUTCOME MEASURES: Mutations in exons 2 to 5 and exon/intron boundaries of the 11-cis retinol dehydrogenase gene. RESULTS: In a compound heterozygote, two novel mutations were found: a 4 bp insertion in exon 2 and a missense mutation Cys267Trp in exon 5. In a second pedigree, a homozygous frameshift mutation in codon 43 (Arg42ct[1-bpdel]) was detected. In both families, the mutations segregate with the disease. The mutations were not found in 50 control individuals. CONCLUSIONS: On the basis of our observations, it is unlikely that mutations in the 11-cis retinol dehydrogenase gene are associated with other, possibly more severe, retinal pathologic conditions/dystrophies or syndromic diseases in which the retina is also affected.