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Characterization of gene expression profiling of mouse tissues obtained during the postmortem interval

ABSTRACT: Attempts to establish a tissue bank from autopsy samples have led to uncovering of the secrets of many diseases. Here, we examined the length of time that the RNA from postmortem tissues is available for microarray analysis and reported the gene expression profile for up- and down-regulated genes during the postmortem interval (PMI). We extracted RNA from fresh-frozen (FF) and formalin-fixed paraffin-embedded (FFPE) brains and livers of three different groups of mice: 1) mice immediately after death, 2) mice that were stored at room temperature for 3 h after death, and 3) mice that were stored at 4°C for 18 h after death, as this storage resembles the human autopsy process in Japan. Based on the microarray analysis, we selected genes that were altered by >1.3-fold or <0.77-fold and classified these genes using hierarchical cluster analysis following DAVID (database for annotation, visualization, and integrated discovery) gene ontology analysis. These studies revealed that cytoskeleton-related genes were enriched in the set of up-regulated genes, while serine protease inhibitors were enriched in the set of down-regulated genes. Interestingly, although the RNA quality was maintained, up-regulated genes were not validated by quantitative PCR, suggesting that these genes may become fragmented or modified by an unknown mechanism.

ORGANISM(S): Mus musculus

PROVIDER: GSE78203 | GEO | 2016/05/13

SECONDARY ACCESSION(S): PRJNA312919

REPOSITORIES: GEO

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Project description:Attempts to establish a tissue bank from autopsy samples have led to uncovering of the secrets of many diseases. Here, we examined the length of time that the RNA from postmortem tissues is available for microarray analysis and reported the gene expression profile for up- and down-regulated genes during the postmortem interval (PMI). We extracted RNA from fresh-frozen (FF) and formalin-fixed paraffin-embedded (FFPE) brains and livers of three different groups of mice: 1) mice immediately after death, 2) mice that were stored at room temperature for 3 h after death, and 3) mice that were stored at 4Â°C for 18 h after death, as this storage resembles the human autopsy process in Japan. Based on the microarray analysis, we selected genes that were altered by >1.3-fold or <0.77-fold and classified these genes using hierarchical cluster analysis following DAVID (database for annotation, visualization, and integrated discovery) gene ontology analysis. These studies revealed that cytoskeleton-related genes were enriched in the set of up-regulated genes, while serine protease inhibitors were enriched in the set of down-regulated genes. Interestingly, although the RNA quality was maintained, up-regulated genes were not validated by quantitative PCR, suggesting that these genes may become fragmented or modified by an unknown mechanism. We extracted RNA from fresh-frozen (FF) brains and livers from mice under three different conditions: 1) mice just after death as a control, 2) mice that were stored at room temperature for 3 h after death, and 3) mice that were stored at 4Â°C for 18 h after death to resemble the human autopsy process. We also created formalin-fixed paraffin-embedded (FFPE) tissue blocks at the same time using mouse organs obtained under the three conditions described above. We then purified RNA from the FFPE tissue blocks. Furthermore, we performed microarray analysis to examine changes in the gene expression profiles during the postmortem interval in FF samples and to compare ene expression profiles between FF and FFPE samples at three different postmortem times as described for the FF samples.

Project description:Background: Molecular adaptations in the striatum mediated by dopamine (DA) denervation or Levodopa (L-dopa) treatment have been implicated with the motor deficits found in Parkinsonâs disease (PD). Alterations in glutamatergic neurotransmission and anti-oxidant mechanisms are reported to play important roles in mediating these changes. However, the mechanisms mediating the molecular adaptations in the striatum are not well understood. In recent years, microRNAs (miRNAs) have been recognized as potent post-transcriptional regulators of gene expression with fundamental roles in numerous biological processes. miRNAs are known to influence the development and maintenance of striatal neurons. To determine the contribution of miRNAs in molecular adaptations found in PD, we screened the expression of 800 miRNAs in postmortem striatum samples obtained from PD and neurologically normal controls. We detected the expression of approximately 250 miRNAs in postmortem human putamen samples collected from patients with PD and healthy controls. There was an abundance of a subset of 17 miRNAs (10 up- and 7 down-regulated) differing substantially between PD and the control, suggesting that miRNAs are altered in the striatum during the course of PD. Computational analysis show that many of these miRNAs targets pro-inflammatory factors in the striatum. Therefore, we sought to detrmine the expression of experimentally validated pro-inflammatory transcripts in PD striatum. Methods: Using a digital gene expression platform to quantify 134 gene transcripts, we compared human postmortem putamen tissues from patients with PD and neurologically normal controls. Results: We identified deregulated expression of 10 gene transcripts (4 up- and 6 down-regulated mRNAs) in postmortem human putamen samples collected fromPD patients compared to controls. The expression of these genes negative correlates with the expression of many of the differentially epxressed miRNAs. Moreover, many of these genes are predicted targets of the differentially expressed miRNAs. Conclusions: We identified deregulated mRNAs most likely associated with anti-oxidant mechanims in PD striatum. This approach may provide insights into pathogenesis of the disease. Human postmortem putamen tissues from 12 patients with PD symptoms and 12 neurologically normal controls were used in the study. Samples were obtained from the Human Brain and Spinal Fluid Resource Center, Los Angeles, CA through NIH NeuroBioBank, and stored at -80Â°C until RNA isolation. Total RNA was extracted using the mirVana RNA isolation kit, following the manufacturerâs instructions (Ambion). Using 225ng total RNA, mRNA levels were assayed by direct digital detection using Nanostring nCounter assay kits (Nanostring Technologies).

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Characterization of gene expression profiling of mouse tissues obtained during the postmortem interval

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