Rhodopsin: Difference between revisions

From The School of Biomedical Sciences Wiki
Jump to navigation Jump to search
← Older editNewer edit →
109276379 (talk | contribs)
13 edits
No edit summary
Nnjm2 (talk | contribs)
7,735 edits
No edit summary
Line 3: Line 3:
Rhodopsin is a member of the [[GPCR|GPCR family]], which is coupled to the [[G-proteins|G-protein]], [[Transducin(Gt)|transducin]]. Rhodopsin, unlike many other GPCRs is activated by a [[Photon|photon]] of light not by the binding of a ligand. Infact, the ligand ([[11-cis retinal|11-cis retinal]]) is already bound in its inactive state. The photon causes a conformational change in the GPCR which causes activation of the transducin, whose α subunit, then activates [[Cyclic GMP phosphodiesterase|cyclic GMP phosphodiesterase]]&nbsp;<ref>Alberts.B, Johnson.A, Lewis.J, Raff.M, Roberts.K, Walter.P, 2008, Molecular Biology of the Cell, 5th Edition, New York, Garland Science</ref>.&nbsp;  
Rhodopsin is a member of the [[GPCR|GPCR family]], which is coupled to the [[G-proteins|G-protein]], [[Transducin(Gt)|transducin]]. Rhodopsin, unlike many other GPCRs is activated by a [[Photon|photon]] of light not by the binding of a ligand. Infact, the ligand ([[11-cis retinal|11-cis retinal]]) is already bound in its inactive state. The photon causes a conformational change in the GPCR which causes activation of the transducin, whose α subunit, then activates [[Cyclic GMP phosphodiesterase|cyclic GMP phosphodiesterase]]&nbsp;<ref>Alberts.B, Johnson.A, Lewis.J, Raff.M, Roberts.K, Walter.P, 2008, Molecular Biology of the Cell, 5th Edition, New York, Garland Science</ref>.&nbsp;  


There are three mutations in the rhodopsin genes, two of which are transition mutations occuring at seperate [[Nucleotides|nucleotides]]&nbsp;of [[Codon|codon]] 347 and one transversion mutation occuring at codon 58. The two transition mutations involve C changing to T. The transversion mutation involves C changing to G&nbsp;<ref>Dryja TP et al (1990) Mutations within the rhodopsin gene in patients with autosomal dominant retinitis pigmentosa. N Engl J Med. 1990 Nov 8;323(19):1302-7.</ref>.  
There are three mutations in the rhodopsin genes, two of which are transition mutations occuring at seperate [[Nucleotides|nucleotides]]&nbsp;of [[Codon|codon]] 347 and one transversion mutation occuring at codon 58. The two transition mutations involve [[Cytosine|C]] changing to [[Thymine|T]]. The transversion mutation involves [[Cytosine|C]] changing to [[guan|G]]&nbsp;<ref>Dryja TP et al (1990) Mutations within the rhodopsin gene in patients with autosomal dominant retinitis pigmentosa. N Engl J Med. 1990 Nov 8;323(19):1302-7.</ref>.  


"[[Retinitis Pigmentosa|Retinitis Pigmentosa]]" is an inherited disease that causes blindness or stationary night blindness, by degenerating retina cells. It might be an [[Autosomal dominant|autosomal dominant]] or recessive and [[X-linked recessive|X-linked recessive]] disease, at which a mutation in the gene encoding rhodopsin. [[Vitamin A|Vitamin A]] improves the condition&nbsp;<ref name="Kelly, J (2011)">Kelly, J, (2011) Retinitis Pigmentosa 4; RP4,OMIM.org (lasst isited 20/11/2011)</ref><ref>Thaddeus P. Dryja, M.D., Terri L. McGee, B.A., Lauri B. Hahn, M.S., et al. Mutations within the rhodopsin gene in patients with autosomal dominant retinitis pigmentosa. N Engl J Med 1990; 323:1302-1307.</ref>.Vitamin A is found naturally in many foods. A variety of meat and fish contain the useful vitamin, along with vegetables such as Carrots which contain large amounts of Beta Carotene.  
"[[Retinitis Pigmentosa|Retinitis Pigmentosa]]" is an inherited disease that causes blindness or stationary night blindness, by degenerating retina cells. It might be an [[Autosomal dominant|autosomal dominant]] or recessive and [[X-linked recessive|X-linked recessive]] disease, at which a mutation in the gene encoding rhodopsin. [[Vitamin A|Vitamin A]] improves the condition&nbsp;<ref name="Kelly, J (2011)">Kelly, J, (2011) Retinitis Pigmentosa 4; RP4,OMIM.org (lasst isited 20/11/2011)</ref><ref>Thaddeus P. Dryja, M.D., Terri L. McGee, B.A., Lauri B. Hahn, M.S., et al. Mutations within the rhodopsin gene in patients with autosomal dominant retinitis pigmentosa. N Engl J Med 1990; 323:1302-1307.</ref>.Vitamin A is found naturally in many foods. A variety of meat and fish contain the useful vitamin, along with vegetables such as Carrots which contain large amounts of Beta Carotene.  
Line 9: Line 9:
=== Retinitis Pigmentosa  ===
=== Retinitis Pigmentosa  ===


Retinitis Pigmentosa is often linked with early-onset cystoid macular edema associated with the p.P347L mutation in the gene coding for Rhodopsin.  
[[Retinitis Pigmentosa|Retinitis Pigmentosa]] is often linked with early-onset cystoid macular edema associated with the p.P347L mutation in the gene coding for Rhodopsin.  


A family of people, all sufferers of Retinitis Pigmentosa and all of whom have the p.P347L mutation in RHO, took part in an experiment to prove the link between these conditions. The participants were a 44 year-old mother, her two daughters aged 17 and 15, and two sons aged 13 and 11. A number of experimental techniques used to determine the functionality and anatomy of the retina were peformed upon all of the family members, these included Funduscopy, Goldmann perimetry, spectral domain optical coherence tomography and electroretinogram.  
A family of people, all sufferers of Retinitis Pigmentosa and all of whom have the p.P347L mutation in RHO, took part in an experiment to prove the link between these conditions. The participants were a 44 year-old mother, her two daughters aged 17 and 15, and two sons aged 13 and 11. A number of experimental techniques used to determine the functionality and anatomy of the retina were peformed upon all of the family members, these included Funduscopy, Goldmann perimetry, spectral domain optical coherence tomography and electroretinogram.  
Line 15: Line 15:
The results of the spectral domain optical coherence tomography showed [[Foveal Atrophy|foveal atrophy]] in the case of the mother, she also showed poor visual acuity of light perception in both eyes. The results of the Funduscopy in the cases of the four children showed nothing out of the ordinary, however, the spectral domain optical coherence tomography showed they all had bilateral cystoid macular edema, and the electroretinogram showed the children had decreased cone response and no rod response at all.  
The results of the spectral domain optical coherence tomography showed [[Foveal Atrophy|foveal atrophy]] in the case of the mother, she also showed poor visual acuity of light perception in both eyes. The results of the Funduscopy in the cases of the four children showed nothing out of the ordinary, however, the spectral domain optical coherence tomography showed they all had bilateral cystoid macular edema, and the electroretinogram showed the children had decreased cone response and no rod response at all.  


The conclusion drawn from these experiments was that there is a strong possibility that cystoid macular edema in patients with Retinitis Pigmentosa could be linked to the p.P347L gene mutation within the rhodopsin gene. Further experiments on more patients with Retinitis Pigmentosa would be needed in order to confirm this&nbsp;<ref name="retinitispigmentosa">Kim C, Chung H, Yu HG. (June 2012). Association of p.P347L in the rhodopsin gene with early-onset cystoid macular edema in patients with retinitis pigmentosa.. . 2 (33), 96-99.</ref><ref>Kim C, Chung H, Yu HG. (June 2012). Association of p.P347L in the rhodopsin gene with early-onset cystoid macular edema in patients with retinitis pigmentosa.. . 2 (33), 96-99</ref>.<br>  
The conclusion drawn from these experiments was that there is a strong possibility that cystoid macular edema in patients with Retinitis Pigmentosa could be linked to the p.P347L [[gene|gene]] mutation within the rhodopsin gene. Further experiments on more patients with [[Retinitis Pigmentosa|Retinitis Pigmentosa]] would be needed in order to confirm this&nbsp;<ref name="retinitispigmentosa">Kim C, Chung H, Yu HG. (June 2012). Association of p.P347L in the rhodopsin gene with early-onset cystoid macular edema in patients with retinitis pigmentosa.. . 2 (33), 96-99.</ref><ref>Kim C, Chung H, Yu HG. (June 2012). Association of p.P347L in the rhodopsin gene with early-onset cystoid macular edema in patients with retinitis pigmentosa.. . 2 (33), 96-99</ref>.<br>  


=== References  ===
=== References  ===


<references />
<references />

Revision as of 11:29, 27 October 2012

Rhodopsin is the photoreceptor protein in rod cells of vertebrate retina [1]. It is also known as opsin 2.

Rhodopsin is a member of the GPCR family, which is coupled to the G-protein, transducin. Rhodopsin, unlike many other GPCRs is activated by a photon of light not by the binding of a ligand. Infact, the ligand (11-cis retinal) is already bound in its inactive state. The photon causes a conformational change in the GPCR which causes activation of the transducin, whose α subunit, then activates cyclic GMP phosphodiesterase [2]. 

There are three mutations in the rhodopsin genes, two of which are transition mutations occuring at seperate nucleotides of codon 347 and one transversion mutation occuring at codon 58. The two transition mutations involve C changing to T. The transversion mutation involves C changing to G [3].

"Retinitis Pigmentosa" is an inherited disease that causes blindness or stationary night blindness, by degenerating retina cells. It might be an autosomal dominant or recessive and X-linked recessive disease, at which a mutation in the gene encoding rhodopsin. Vitamin A improves the condition [4][5].Vitamin A is found naturally in many foods. A variety of meat and fish contain the useful vitamin, along with vegetables such as Carrots which contain large amounts of Beta Carotene.

Retinitis Pigmentosa

Retinitis Pigmentosa is often linked with early-onset cystoid macular edema associated with the p.P347L mutation in the gene coding for Rhodopsin.

A family of people, all sufferers of Retinitis Pigmentosa and all of whom have the p.P347L mutation in RHO, took part in an experiment to prove the link between these conditions. The participants were a 44 year-old mother, her two daughters aged 17 and 15, and two sons aged 13 and 11. A number of experimental techniques used to determine the functionality and anatomy of the retina were peformed upon all of the family members, these included Funduscopy, Goldmann perimetry, spectral domain optical coherence tomography and electroretinogram.

The results of the spectral domain optical coherence tomography showed foveal atrophy in the case of the mother, she also showed poor visual acuity of light perception in both eyes. The results of the Funduscopy in the cases of the four children showed nothing out of the ordinary, however, the spectral domain optical coherence tomography showed they all had bilateral cystoid macular edema, and the electroretinogram showed the children had decreased cone response and no rod response at all.

The conclusion drawn from these experiments was that there is a strong possibility that cystoid macular edema in patients with Retinitis Pigmentosa could be linked to the p.P347L gene mutation within the rhodopsin gene. Further experiments on more patients with Retinitis Pigmentosa would be needed in order to confirm this [6][7].

References

  1. ↑ Hargrave P.A., McDowell J.H.(1992) Rhodopsin and phototransduction: a model system for G protein-linked receptors. The FASEB Journal, 6(6), 2323-2331
  2. ↑ Alberts.B, Johnson.A, Lewis.J, Raff.M, Roberts.K, Walter.P, 2008, Molecular Biology of the Cell, 5th Edition, New York, Garland Science
  3. ↑ Dryja TP et al (1990) Mutations within the rhodopsin gene in patients with autosomal dominant retinitis pigmentosa. N Engl J Med. 1990 Nov 8;323(19):1302-7.
  4. ↑ Kelly, J, (2011) Retinitis Pigmentosa 4; RP4,OMIM.org (lasst isited 20/11/2011)
  5. ↑ Thaddeus P. Dryja, M.D., Terri L. McGee, B.A., Lauri B. Hahn, M.S., et al. Mutations within the rhodopsin gene in patients with autosomal dominant retinitis pigmentosa. N Engl J Med 1990; 323:1302-1307.
  6. ↑ Kim C, Chung H, Yu HG. (June 2012). Association of p.P347L in the rhodopsin gene with early-onset cystoid macular edema in patients with retinitis pigmentosa.. . 2 (33), 96-99.
  7. ↑ Kim C, Chung H, Yu HG. (June 2012). Association of p.P347L in the rhodopsin gene with early-onset cystoid macular edema in patients with retinitis pigmentosa.. . 2 (33), 96-99
Retrieved from "https://teaching.ncl.ac.uk/bms/wiki//index.php?title=Rhodopsin&oldid=6979"