Question

Scenario 1.  

A recent research publication connected migraine headache frequency with a single nucleotide polymorphism.  The affected gene encodes the TRPM8 channel protein that transports ions across a membrane.  Interestingly, this genetic variation may have become common in northern European populations because it also grants them a higher tolerance to cold temperatures

1.  Sequencing of the TRPM8 gene and the surrounding region of the chromosome has been completed.

1. Describe how you know where transcription of this gene would start.
2. Describe how you know where translation of this gene would start.

2.  Using the TRPM8 gene/protein as an example, indicate where you would find this type of bond, what they are made from, and describe how they are formed.

a)  phosphodiester bonds

b)  peptide bonds

3.  A new TRPM8 mutation has been identified in a family in Indiana.  This protein has a missense mutation in the sequence that results in a mutation labelled T118S.

a)  What does this mutation notation indicate?

b)  Using the genetic code, dictate the RNA sequence for this region.

c)  What is the DNA sequence of the template strand for this region?

Answer 1

1. a. Ans:

Transcription and Translation:

TRPM8 is being potentially one such gene, the only known receptor for the sensation of moderate cold temperature.

TRPM8 single nucleotide polymorphisms (SNP’s) are being associated with both migraine with and without aura, and show little selectivity for any of the migraine characteristics. The SNPs rs7577262 & rs10166942 are 7 kb and 950 bp upstream of the transcription start site for TRPM8 mRNA, respectively. Carriers of the rarer allele of rs10166942 (C; C or C; T) have a lower risk of migraine, compared with those carrying two common alleles (T; T). Another SNP rs17862920 is in the first intron of TRPM8 gene. It is to be tested whether and how the 3 variants alter the TRPM8 expression level which involves in transcriptional regulations.

According a recent study suggests that some TRPM8 SNP variants causing amino acid substitutions affect the expression level as well as the function of TRPM8 channels in cell lines, providing support for the idea that the variants identified in migraine patients may indeed impact channel expression/function.

2.a. Answer: Polydiester and Peptide bonds:

Polyester is being comprised of repeated units of R-3-hydroxybutyrate, which forms a polymeric chain, poly-(R)-3-hydroxybutyrate (PHB). This modification PHB-ylation by analogy with the established protein modifications.

PHB (poly-(R)-3-hydroxybutyrate) peptide bonds are metabolic precursors, presumably acts like cofactor for the enzymatic reaction in which a covalent bond to the protein is formed and plays an important role in protein folding, protein sorting, or retention of inorganic polyphosphate (polyP).

According to this, the role and specific sites of the molecular interaction between PHB and TRPM8 remained unclear.

Polyester is having substantial structural and functional impacts on the protein. The high-energy C-terminal CoA-ester group, derived from PHB metabolic precursors, presumably acts like cofactor for the enzymatic reaction in which a covalent bond to the protein is formed

Polyphosphate (polyP) is an inorganic polymer built of tens to hundreds of phosphates, linked by high-energy phosphoanhydride bonds. PolyP forms complexes and modulates activities of many proteins including ion channels. The polydiester bonds used in the function of the transient receptor potential melastatin 8 (TRPM8) channel. Thus the TRPM8 protein forms a stable complex with polyP and its presence is essential for normal channel activity.

3. Answer:

a. Mutations in indiana family is well tolerated with cold climate temperatures.

b and c Answer: TRPM8 single nucleotide polymorphisms (SNP’s) are being associated with both migraine with and without aura, and show little selectivity for any of the migraine characteristics. The SNPs rs7577262 & rs10166942 are 7 kb and 950 bp upstream of the transcription start site for TRPM8 mRNA, respectively. Carriers of the rarer allele of rs10166942 (C; C or C; T) have a lower risk of migraine, compared with those carrying two common alleles (T; T). Another SNP rs17862920 is in the first intron of TRPM8 gene. It is to be tested whether and how the 3 variants alter the TRPM8 expression level which involves in transcriptional regulations.