Preservation of RNA for functional analysis of separated alleles in yeast: comparison of snap-frozen and RNALater (R) solid tissue storage methods

Background: The aim of the present study was to compare RNALater (R) with the usual method of liquid nitrogen snap freezing as a surrogate mRNA preservation method for functional analysis of separated alleles in yeast (FASAY). Methods: A total of 81 patients with transitional cell carcinoma of the bladder underwent fresh tissue biopsies directly transferred into RNALater (R) and stored at room temperature or at 4 degrees C for increasing time intervals until RNA processing. From this cohort of patients, 53 paired snap-frozen and RNALater (R) preservative-suspended tissues were obtained. Samples immediately frozen in liquid nitrogen were further stored at -80 degrees C. Results: Of the 81 RNALater (R) samples, 14 were not processed for FASAY because of RNA degradation. Of the remaining 67 samples, 15 (22%) were FASAY-positive. Identical FASAY results were found for 50 of 53 (94.4%) paired samples and the percentage of red yeast colonies was highly correlated (Cohen's kappa < 0.82; p < 0.00001). A single p53 missense mutation was found in each of the three discordant positive FASAY and was identical in each concordant positive sample (10/53). Storing samples in RNALater (R) at room temperature for 3 days and at 4 degrees C for less than 1 month provided high-quality mRNA suitable for FASAY. Conclusions: Our results demonstrate that RNALater (R) is a suitable and flexible alternative to snap freezing for FASAY analysis.