Peripherin-2 is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
, that in humans is encoded by the ''PRPH2''
gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
.
Peripherin-2 is found in the rod and cone cells of the
retina
The retina (; or retinas) is the innermost, photosensitivity, light-sensitive layer of tissue (biology), tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a focus (optics), focused two-dimensional ...
of the
eye
An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system.
In higher organisms, the ey ...
. Defects in this protein result in one form of
retinitis pigmentosa
Retinitis pigmentosa (RP) is a member of a group of genetic disorders called inherited retinal dystrophy (IRD) that cause loss of vision. Symptoms include trouble seeing at night and decreasing peripheral vision (side and upper or lower visua ...
, an incurable blindness.
Mutations in the PRPH2 gene are associated with
Vitelliform macular dystrophy.
Function
The protein encoded by this gene is a member of the transmembrane 4 superfamily, also known as the
tetraspanin
Tetraspanins are a family of membrane proteins found in all multicellular eukaryotes also referred to as the transmembrane 4 superfamily (TM4SF) proteins. These proteins have four transmembrane alpha-helices and two extracellular domains, one sh ...
family. Most of these members are cell-surface proteins that are characterized by the presence of four transmembrane helices. Tetraspanins mediate signal transduction events that play a role in the regulation of cell development, activation, growth and motility.
Peripherin 2 (sometimes referred to as peripherin/RDS or simply RDS) is a cell surface
glycoprotein
Glycoproteins are proteins which contain oligosaccharide (sugar) chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known a ...
found in the outer segment of both rod and cone photoreceptor cells. It is located in the rim regions of the flattened disks that contain
rhodopsin
Rhodopsin, also known as visual purple, is a protein encoded by the ''RHO'' gene and a G-protein-coupled receptor (GPCR). It is a light-sensitive receptor protein that triggers visual phototransduction in rod cells. Rhodopsin mediates dim ...
, which is the protein that is responsible for initiation of visual phototransduction upon reception of light. Peripherin 2 may function as an
adhesion molecule involved in stabilization and compaction of
outer segment disks or in the maintenance of the curvature of the rim. This protein is essential for disk
morphogenesis
Morphogenesis (from the Greek ''morphê'' shape and ''genesis'' creation, literally "the generation of form") is the biological process that causes a cell, tissue or organism to develop its shape. It is one of three fundamental aspects of deve ...
.
Clinical significance
Defects in this gene are associated with both central and peripheral retinal degenerations. Some of the various phenotypically different disorders are autosomal dominant
retinitis pigmentosa
Retinitis pigmentosa (RP) is a member of a group of genetic disorders called inherited retinal dystrophy (IRD) that cause loss of vision. Symptoms include trouble seeing at night and decreasing peripheral vision (side and upper or lower visua ...
, progressive
macular degeneration
Macular degeneration, also known as age-related macular degeneration (AMD or ARMD), is a medical condition which may result in blurred vision, blurred or vision loss, no vision in the center of the visual field. Early on there are often no sym ...
,
macular dystrophy and retinitis pigmentosa digenic.
References
External links
GeneReviews/NIH/NCBI/UW entry on Retinitis Pigmentosa Overview
Further reading
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