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RDH5
retinol dehydrogenase 5
The RDH5 gene provides instructions for making an enzyme essential for normal vision, particularly in low-light conditions, by playing a key role in the visual cycle within the eye. The RDH5 gene encodes the 11-cis retinol dehydrogenase 5 enzyme, which is vital for maintaining the visual cycle in the retina.
RDH5 is located on the long (q) arm of chromosome 12, at band 12q13.2. Arm ratio per GRCh38 - banding schematic.
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Overview
The RDH5 gene, also known as retinol dehydrogenase 5, is fundamental for human vision. It directs the production of an enzyme, 11-cis retinol dehydrogenase 5, which is particularly important for sight in dim light conditions.
This enzyme is predominantly located in the retinal pigment epithelium (RPE), a layer of cells at the back of the eye that provides support and nourishment to the light-sensitive retina. Its activity is integral to the biochemical pathway known as the visual cycle, enabling the eye to adapt to varying light levels.
What the gene does
The primary function of the RDH5 gene product, 11-cis retinol dehydrogenase 5, is to facilitate a crucial step in the visual cycle. This multi-step process converts light into electrical signals, which are then transmitted to the brain for interpretation as vision. A key aspect of this cycle involves the recycling of 11-cis retinal, a form of vitamin A necessary for light-to-signal conversion.
Specifically, the 11-cis retinol dehydrogenase 5 enzyme converts 11-cis retinol into 11-cis retinal. In photoreceptor cells within the retina, 11-cis retinal combines with opsin proteins to form photosensitive pigments. When light strikes these pigments, 11-cis retinal transforms into all-trans retinal, initiating a cascade of chemical reactions that generate electrical signals. The RDH5 enzyme then helps convert all-trans retinal back to 11-cis retinal, allowing the visual cycle to continue. Rod photoreceptors, responsible for low-light vision, heavily rely on 11-cis retinol dehydrogenase 5 for 11-cis retinal production, while cone photoreceptors, involved in bright light and colour vision, also utilise it, albeit possibly with additional pathways.
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Chromosome location
The RDH5 gene is situated on chromosome 12 at position 12q13.2. This specific genomic location indicates its address within the human genome. The gene provides instructions for a protein comprising 318 amino acids.
Protein structure
Domain architecture has not been experimentally characterised in detail for this protein.
Key variants
Variants within the RDH5 gene can affect the production or function of the 11-cis retinol dehydrogenase 5 enzyme. These genetic changes can lead to a reduction or complete loss of enzyme activity. The consequences of such variants typically relate to disruptions in the visual cycle, impacting the eye's ability to process light effectively.
No pathogenic or likely-pathogenic ClinVar variants recorded yet for this gene.
Associated conditions
Variants in the RDH5 gene are associated with inherited eye conditions that affect vision. One such condition is fundus albipunctatus. Individuals with this condition typically experience impaired night vision and develop characteristic whitish-yellow flecks across the retina. These symptoms arise from the enzyme's diminished function, leading to an insufficient supply of 11-cis retinal.
No disease links recorded for this gene in our reference set.
UK clinical status
The RDH5 gene is included in the NHS Genomic Medicine Service's green list for Retinal disorders (R32). This indicates that testing for variants in this gene is considered clinically appropriate for diagnostic purposes within the NHS for this condition.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does the RDH5 gene do?
The RDH5 gene provides instructions for making the 11-cis retinol dehydrogenase 5 enzyme, which is crucial for the visual cycle in the eye. This enzyme helps convert light into electrical signals, especially important for vision in low-light conditions.
What conditions are associated with RDH5 gene variants?
Variants in the RDH5 gene are associated with fundus albipunctatus, an inherited eye condition characterised by impaired night vision and distinctive whitish-yellow flecks in the retina.
Is the RDH5 gene tested within the NHS?
Yes, the RDH5 gene is part of the NHS Genomic Medicine Service's green list for testing in relation to retinal disorders (R32), indicating its clinical relevance for diagnosis within the NHS.
References
- Skorczyk-Werner A, Pawłowski P, Michalczuk M. Fundus albipunctatus: review of the literature and report of a novel RDH5 gene mutation affecting the invariant tyrosine (p.Tyr175Phe). Journal of applied genetics. 2015. PMID: 25820994
- Sergouniotis PI, Sohn EH, Li Z. Phenotypic variability in RDH5 retinopathy (Fundus Albipunctatus). Ophthalmology. 2011. PMID: 21529959
- Schatz P, Preising M, Lorenz B. Lack of autofluorescence in fundus albipunctatus associated with mutations in RDH5. Retina (Philadelphia, Pa.). 2010. PMID: 20829743
- Driessen CA, Winkens HJ, Hoffmann K. Disruption of the 11-cis-retinol dehydrogenase gene leads to accumulation of cis-retinols and cis-retinyl esters. Molecular and cellular biology. 2000. PMID: 10825191