Signal recognition particle receptor (SRPR) is downregulated in a rat model of cyclosporin A-induced gingival overgrowth.

Differential display is a powerful technique which can be used to identify those genes whose expression is altered between two or more tissues under investigation. We have applied differential display to a rat model of cyclosporin A-induced gingival overgrowth (CIGO) to identify genes which are differentially expressed as a result of drug treatment. Ten weanling Wistar rats were fed with a pelleted diet containing cyclosporin A (CsA) at 120 mg/kg for 10 d and then 200 mg/kg for a further 30 d prior to culling. Experimental rats were compared with 10 age/sex-matched rats on a control diet. Significant evidence of overgrowth was observed in the interdental papilla between the mandibular first and second molar teeth in the CsA group. Differential display was performed on total cellular RNA extracted from the mandibular buccal gingiva. A cDNA product was isolated which was underexpressed in the overgrowth tissue and demonstrated a 95% sequence homology to the human signal recognition particle receptor (Human Docking Protein). Preliminary studies indicate that this gene is also underexpressed in human CIGO tissue. The method of approach and the potential implications of our findings are discussed.