You want to study how the localization of wildtype FMRP chan

You want to study how the localization of wildtype FMRP changes in response to different types of stimulation in a live brain slice preparation. In order to monitor the localization of this protein in vivo, you decide to knock-in a GFP-tagged FMRP to the endogenous locus. You obtain a mouse strain that has a floxed FMRP locus, as well as a Cre strain that expresses the recombinase only in a subset of neurons in the brain.

Once you\'ve created these FMRP-GFP mice, you perform an experiment by stimulating a group of neurons expressing GFP-FMRP with a high frequency stimulus. Based on what is known about FMRP\'s function, what changes do you expect to see in the protein\'s localization?

After the first experiment, you stimulate these cells with a lower frequency (1Hz) stimulus for 15 minutes. Control is not stimulated. You then preserve the tissue, and stain it with an antibody that specifically recognizes only phosphorylated FMRP. If you compare the amount of phosphorylated FMRP in this brain slice to the amount in a slice which had not received a 1 Hz stimulus, what kind of change would you expect to see?

Solution

FMR is the gene that codes for protein FMRP, found in the brain. Mutation in the gene results in fragile x syndromes, autism, premature ovarian failure and Parkinsons dieease. FMR gene is located on the x chromosome and carries CGG trinucleotide. Fragile x syndromes is caused by the expansion of CGG trinucleotide. FMRP is a dendritic mRNA binding protein which regulates cytoplasmic mRNA and are associated with polyribosomes. And RNA binding property depends on KH domain. FMRP function as translation suppressor. FMRp binds to RNA and regulate mGluR, metabotropic glutamate receptor mediated translation. FMRP loss results in the increased level of protein synthesis and stops mGluR dendritic translation.

Phosphorlated FMRP is associated with polyribisomes and phosphorylated FMRP hinders the translation process.