Studying expression level of some genes involved in the formation of post-traumatic stress disorder associated fear memory by qPCR

Author: Tamazi Giunashvili
Keywords: PTSD, Genes expression, mRNA, RT-qPCR, Memory, Mice
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Post-traumatic stress disorder (PTSD) develops in individuals as a result of certain types of stress, shock, sexual violence, war, or other life-threatening incidents. This research focuses on the roles of glutamatergic and GABAergic systems in mouse Amygdala and Hippocampus with the expression of specific genes in the context of fear memory by q-PCR. q-PCR was used to determine the mRNA transcription profiles of 5 putative reference genes - HPRT, B2m, Tbp, Pol2a, 18S - as normalization factors and 4 different target genes SHANK1, HOMER1, GRM5, and FKBP5 which are involved in the pathophysiology of PTSD. For comparison of the different RNA transcription levels, the Ct values were directly compared. All samples were amplified in triplicate and for statistical analysis T-test was used. The range was defined as the difference between the lowest and the highest RNA transcription (low Ct value) in all tissues, based on the same amount of cDNA used in the PCR. Preliminary results revealed a statistically significant decrease in the expression of Grm5 (coding for metabotropic glutamate receptor 5, mGluR5) and Shank1(SH3/ankyrin domain gene 1) genes in the Hippocampus of PTSD-associated fear memory. There was an interesting tendency of increased gene expression in the normal fear memory group compared to controls. The same tendency was observed for the rest of the genes: Fkbp5 (FK506 binding protein 5) and Homer1 (homer homolog 1). Statistically significant changes in the expression of Shank1 and Homer1 were detected in the Amygdala. It is shown that the glucocorticoid receptor (GR) requires higher levels of corticosterone to be activated. Products of these genes are crucial components of excitatory synapses and changes in their expression levels could serve as a molecular marker for enhanced/diminished synaptic connections. To conclude, our work has disclosed some differences between normal and PTSD-associated fear memories on distinct levels of organization.