Microarray Analysis and Description of Smr1 Gene in Rat Penis in a Post-Radical Prostatectomy Model of Erectile Dysfunction

PURPOSE: We focused on the post-radical prostatectomy model to advance the understanding of neurogenic erectile dysfunction. We attempted to identify previously undescribed molecular changes via gene discovery methods using GeneChip (Affymetrix, Santa Clara, California) microarray technology. MATERIALS AND METHODS: Five male adult 120-day-old Sprague-Dawley rats underwent bilateral cavernous nerve neurectomy. Five age matched controls were prepared simultaneously. The penises were harvested on postoperative day 2 and snap frozen in liquid nitrogen. RNA was prepared and pooled into cut and uncut groups. Synthesis of cRNA was performed according to the GeneChip technical manual. Microarray analysis was performed on a U34A Rat Array (Affymetrix). This array has approximately 8,800 gene probe sets, approximately 6,600 known genes and approximately 2,200 estimated sequence transcripts. RESULTS: Dramatic results were found during GeneChip microarray expression analysis. A total of 126 candidate genes were noted to be altered based on the magnitude of expression change using rigorous statistical criteria, including 47 that were down-regulated and 79 that were up-regulated. Among the many significant changes seen 1 dominant class of genes was the submandibular rat genes. Submandibular rat 1 (SMR1) was down-regulated 82.5 fold. Other genes in this family were down-regulated 226 and 90 times. This result was confirmed by reverse transcriptase-polymerase chain reaction and Western blot analyses. These assays verified decreases in SMR1 at multiple time points after surgery. CONCLUSIONS: Impressive and previously unrecognized genetic changes are being intensely investigated as they are being unmasked by GeneChip technology. We have identified and begun the investigation of 1 interesting family of genes, namely submandibular gland proteins. The role of SMR as a clinically relevant change in penile and/or urethral function following cavernous nerve injury is speculative.