Identification of circadian gene expression in the rat pineal gland and retina by mRNA differential display.

To identify unique gene products that could be crucial for circadian and light-dark regulations, using the technology of differential display, we have investigated mRNAs that were isolated from rat pineals and retinas collected either during subjective day (D) or subjective night (N). A subpopulation of about 50 mRNAs were amplified from pineal using designed primers and reverse transcriptase-polymerase chain reaction. Thirty five of the mRNAs were expressed equivalently in both D and N samples. From the 15 mRNAs showing differential expression, four amplified products were selected, based on higher expression during the subjective night (N310, N320, N383, N420) and each was subcloned and sequenced. Of the four cDNAs studied, only N310 was determined to have significant identity to a known cell adhesion protein, called F3. This protein is highly expressed in developing mouse neurons and is related to chicken contactin. Each differentially displayed product identified is being examined further in order to understand their potential significance in the circadian regulation of pineal and retinal activities.