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PRCD
photoreceptor disc component
PRCD is located on the long (q) arm of chromosome 17, at band 17q25.1. Arm ratio per GRCh38 - banding schematic.
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Overview
PRCD (photoreceptor disc component) is located on chromosome 17 at band q25.1 and encodes a small protein integral to photoreceptor structure. Photoreceptors are the light-sensitive cells in the retina responsible for converting photons into electrical signals that the brain interprets as vision. The PRCD protein localises to the connecting cilium and outer segment discs of rod and cone photoreceptors, regions critical for phototransduction.
Variants in PRCD have been extensively documented in veterinary medicine, where they cause progressive retinal atrophy in multiple dog breeds. In humans, the gene's contribution to inherited retinal disease is less well defined, though some studies suggest possible involvement in photoreceptor maintenance. Research continues to clarify whether pathogenic variants in human PRCD underlie retinal degeneration phenotypes.
What the gene does
The PRCD protein plays a structural role in photoreceptor outer segments, the specialised compartments where light detection occurs. Outer segments comprise hundreds of stacked membranous discs containing the visual pigment rhodopsin in rods, or cone opsins in cones. These discs are continuously renewed throughout life, requiring precise assembly and turnover mechanisms to maintain visual function.
PRCD localises to the connecting cilium, a narrow bridge linking the photoreceptor inner and outer segments, and to the outer segment disc membranes themselves. Evidence suggests the protein participates in disc membrane morphogenesis and stabilisation, helping to organise the tightly packed disc structure necessary for efficient photon capture. Without proper disc architecture, photoreceptors cannot sustain normal phototransduction, leading to progressive cellular dysfunction and eventual degeneration.
The protein appears to interact with other photoreceptor-specific molecules involved in outer segment biogenesis, though the precise molecular pathways remain incompletely understood. Research in animal models indicates that loss of PRCD function disrupts disc alignment and membrane integrity, triggering photoreceptor apoptosis over time.
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Chromosome location
PRCD resides on the long arm of chromosome 17 at cytogenetic band 17q25.1, near the telomeric end of the chromosome. The genomic locus is relatively compact, though detailed exon structure and transcript variants have not been exhaustively catalogued in public databases. The chromosomal region 17q25 harbours several genes involved in sensory and neurological functions, reflecting evolutionary clustering of tissue-specific genes.
Protein structure
Domain architecture has not been experimentally characterised in detail for this protein. Current structural annotations suggest PRCD is a small polypeptide with predicted transmembrane or membrane-associated regions, consistent with its localisation to photoreceptor disc membranes and the connecting cilium. The absence of well-defined conserved domains in sequence databases may reflect the protein's relatively recent evolutionary origin or its structural divergence from other characterised protein families.
Key variants
Genetic variants in PRCD have been identified across species, with the majority of clinical data derived from canine genetics. In dogs, a specific recessive variant causes progressive retinal atrophy, a condition characterised by gradual photoreceptor loss leading to blindness. Human variants in PRCD are less frequently reported, and their pathogenicity remains under investigation. Variant interpretation requires careful consideration of evolutionary conservation, functional studies, and segregation data, particularly given the limited human phenotypic information currently available.
No pathogenic or likely-pathogenic ClinVar variants recorded yet for this gene.
Associated conditions
No confirmed human inherited conditions are currently attributed to PRCD variants in major genetic databases. The gene's association with progressive retinal atrophy in veterinary medicine has prompted investigation into whether human PRCD variants might contribute to inherited retinal degenerations, such as retinitis pigmentosa or cone-rod dystrophy. To date, however, pathogenic human variants have not been definitively established, and the gene is not routinely included in clinical retinal disease gene panels. Ongoing research seeks to clarify whether rare PRCD variants play a role in human photoreceptor disease.
No disease links recorded for this gene in our reference set.
UK clinical status
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does the PRCD gene do?
PRCD encodes a protein that helps maintain the disc membrane structures within photoreceptor cells in the retina. These discs are essential for detecting light and converting it into visual signals.
Are PRCD variants linked to human eye disease?
Whilst PRCD variants cause progressive retinal atrophy in dogs, confirmed pathogenic variants causing human retinal disease have not been firmly established. Research is ongoing to determine whether rare human PRCD variants contribute to inherited vision loss.
Is PRCD testing available on the NHS?
PRCD is not currently included in NHS genomic medicine panels for inherited retinal conditions, reflecting the limited evidence for pathogenic human variants. Clinical testing focuses on genes with well-documented roles in human retinal degeneration.