A Time Course Study Demonstrating mRNA, microRNA, 18S rRNA, and U6 snRNA Changes to Estimate PMI in Deceased Rat's Spleen

Abstract Determining the postmortem interval ( PMI ) is important in criminal, civil, and forensic cases. We examined the feasibility of using the transcript abundances of m RNA s, 18 S r RNA , U 6 sn RNA , and micro RNA s as a means to estimate the PMI . We removed spleen tissues from rats at different PMI s under 4°C or 25°C and examined gene transcript abundances in these samples by RT ‐q PCR . Using the algorithm geNorm, we found that micro RNA s to be appropriate control markers because they were less affected by PMI and temperature. We also characterized relationships between observed PMI and the transcript levels of the above‐mentioned RNA s. GAPDH 1 and ACTB 1 fluctuated slightly like cubic curves, while GAPDH 2 and ACTB 2 decreased rapidly. 18 S r RNA transcript level exhibited a parabolic‐like trend at 25°C and exponential growth at 4°C, while U 6 transcript level exhibited exponential decay at 25°C and a parabolic‐like trend at 4°C. Following validation, we conclude that GAPDH 2, ACTB 2, and 18 S r RNA are suitable makers in the accurate determination of PMI .