Life-long norepinephrine transporter (NET) knock-out leads to the increase in the NET mRNA in brain regions rich in norepinephrine terminals

Abstract

These studies aimed to identify the genes differentially expressed in the frontal cortex of mice bearing a life-long norepinephrine transporter knock-out (NET-KO) and wild-type animals (WT).Differences in gene expression in the mouse frontal cortex were studied using a whole-genome microarray approach. Using an alternative approach, i.e. RT-PCR (reverse transcription polymerase chain reaction) with primers complementary to various exons of the NET gene, as well as TaqMan arrays, the level of mRNA encoding the NET in other brain regions of the NET-KO mice was also examined. The analyses revealed a group of 92 transcripts (27 genes) that differentiated the NET-KO mice from the WT mice.Surprisingly, the studies have shown that the mRNA encoding NET accumulated in the brain regions rich in norepinephrine nerve endings in the NET-KO mice. Because there is no other source of NET mRNA besides the noradrenergic terminals in the brain regions studied, these results might speak in favor of the presence of mRNA in axon terminals. RNA-Binding Protein Immunoprecipitation approach indicated that mRNA encoding NET was detected in the Ago2 protein/mRNA complex. In addition, the amount of Ago2 protein in the frontal cortex was significantly higher in NET-KO mice as compared with that of the WT animals.These results are important for further characterization of the NET-KO mice, which – besides other merits – might serve as a good model to study the fate of truncated mRNA in neurons.