c-fos Expression
c-fos expression is used as a marker of neuronal activation:
levels of c-fos mRNA and Fos protein are low in control, unhandled animals
if you stimulate an animal--handling, mating, stress, etc., you will see significant increases in the level of these molecules
the rise and fall occurs quickly:
- c-fos mRNA peaks by 30-60 minutes, and declines to basal levels within 2 hours
- Fos protein peaks by 1-2 hour,s and declines to basal levels within 4 hours
the transient nature of c-fos expression as well as the low levels basally enables detection of these molecules to serve as a “marker” of neuronal activation
c-fos expression serves to couple “inputs” (neuronal or hormonal) with gene transcription:
- Fos protein forms a dimer with Jun protein--called “AP-1” factor
- AP-1 factor binds to specific DNA sequences (AP-1 site) to control transcription of genes