Correlation Between Expression Of Circular Rnas And PMI In Mice

Objective To investigate the degrade rules of three kinds of circRNAs in mouse cerebellum and its applicability to the estimation of death time.Methods 50 KM mice were killed and divided into 2 groups randomly,each group of mice were placed in 4℃incubator and 20℃incubator.First 5 mice corpses were dissected immediately,and the others were dissected after 24 h,48 h,96 h,168 h,5 mice each time.Mouse cerebellar tissue was taken,and some were stored in 3%paraformaldehyde solution for HE staining morphology observation,and another part of brain tissue was used to extract total RNA.Expression amount ofβ-actin,Cdr1as circRNA,Rims2 circRNA and Dym circRNA were quantified using an ABI 7500 Real Time PCR System.SPSS19.0 software was used for data analyzing.Result HE staining of mouse cerebellar tissue shows that the changes in cerebellar tissue became more obvious when PMI grows.The change in 20℃ group under the same PMI was more obvious than that of 4℃ group.In the cerebellum of the control group（0h group）,the cerebellar cortex is clearly observed to be divided into three layers:the molecular layer,the Purkinje cell layer,and the granular layer,with no significant changes.After 48 hours,the cerebellar tissues of the 4℃ group have self-digested.After 96 hours,the cells are arranged disorderly,the nucleus have dissolved,fragmented,and pyknosis,the cells were vacuolated.After 168 hours,the molecular layer and the Purkinje cell layer could not be clearly distinguished,the nucleus are rarely seen.But the granular layer is still visible.In the 20℃ group,cerebellar tissue under microscopy showes that cell swelling occurred after dead for24 hours.After 48 hours,cell arrangement was disordered.After 96 hours cell number was significantly reduced（P<0.05）,cortical stratification was blurred.After 168 hours cells are mostly dissolved,stratification is not obvious.Only a small number of nuclei exist.M value of Cdr1as circRNA is the lowest in each group,so it can be used as the reference gene of this experiment.Relative express levels,2^-ΔΔCT value,of Rims2circRNA and Dym circRNA in both two groups are basically decline when PMI rises（P<0.05）.As the result shows,the cubic regression equations of Rims2 circRNA and Dym circRNA in the 4℃ group were highly correlated with PMI.Regression equations are?=1.392+2.691x-0.678x²+0.059x³,r²=0.752,P<0.05;?=3.767+4.034x-1.385x²+0.151x³,r²=0.834,P<0.05,the cubic regression equation of Rims2 circRNA and Dym circRNA in the 20℃ group was moderately correlated with PMI,regression equation are?=3.532+0.170x+0.060x²-0.008x³,r²=0.544,P<0.05;?=5.814-2.172x+0.970x²-0.106x³,r²=0.512,P<0.05.Conclusion 1.With the increase of PMI,the relative expression of circRNAs gradually decreased.2.TheΔCt values of circRNAs in the 4℃ group were highly correlated with PMI,and theΔCt values of circRNAs in the 20℃ group were moderately correlated with PMI.3.CDR1as circRNA is suitable as the internal reference gene for quantitative PCR in this experiment.4.At the same time of death,the morphological changes of the cadaver at 20℃ were more pronounced than at4℃.