Question

6. Signal Transduction in photoreceptor cells

Retinitis Pigmentosa (RP) refers to a heterogeneous group of progressive retinal degenerative diseases that result in various

forms of poor vision. The different forms of the disease are caused by distinct mutations in various genes.

• RP3 is caused by a mutation in RPGR, a gene that encodes a GTPase regulator.

• RP45 is caused by a mutation in CNGB1, a gene that encodes a cyclic nucleotide gate channel.

• RP14 is caused by TULP1, a gene that encodes a protein required for trafficking of rhodopsin to outer discs in rods and

  cones.
  A. For each of the forms of RP listed above briefly describe how an altered form of the protein might result in degeneration of the retina and poor vision. In your description consider the function of photoreceptors. Be as specific as possible indicating which pathways, structures, interactions, etc. which might be altered.

  RP3:

  RP45:

RP14:

please answer all three parts

Answer 1

RP3- RPGR - It is a GTP ase regulated gene. RPGR official name is Retinitis pigmentosa GTPase regulated.It is a protein coding gene.It encodes protein in a series of 6 RCC1 like domains.(RLD).Encoded proteins are formed in golgi body.It interacts with RPGR .This is localized in the external part of the rod photoreceptors and keeps them viable.Mutation in RPGR linked with x linked retinitis pigmentosa(XLRP).

RP45-CNGB1-Cyclic Nucleotide Gated Channel Beta.

*Forms the heterotetramic rod photoreceptor cyclic nucleotide gated channel.

*Regulates electrical response to light.

*Protein coding region of CNGB1.

Consist 12 exons.

Functions-*Protein localization to organelle

*ion,cation transport

*membrane potential regulation

*rhodopsin mediated signalling pathway.

TULP1-Expressed exclusively in retina

*Involved in protein trafficking

*Essential for transport of rhodopsin from site of synthesis in inner segments through connecting cilium to outer segments.

*Homologous to Mouse Tub gene.