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Effects of TrkB-ICD overexpression on the morphology, activity and transcriptome of cultured primary cortical neurons

ABSTRACT: In Alzheimer’s disease (AD), amyloid β (Aβ)-triggered cleavage of TrkB-FL impairs brain-derived neurotrophic factor (BDNF) signaling, thereby compromising neuronal survival, differentiation, as well as synaptic transmission and plasticity. In addition to compromising canonical BDNF signalling pathways, TrkB-FL cleavage produces an intracellular fragment (TrkB-ICD), which was shown to accumulate in the nucleus and to display tyrosine kinase activity. To dissect the role of TrkB-ICD overexpression from the loss of endogenous signaling throught TrkB-FL, we used lentiviruses to overexpress the TrkB-ICD sequence in cultured primary cortical neurons and performed morphological, electrophysiological and transcriptomics studies. While TrkB-ICD overexpression did not affect cell survival, it caused a significant decrease in the number of dendritic spines, both compared to untransduced and GFP-transduced neurons. Furthermore, TrkB-ICD overexpressing neurons presented a hyperpolarized resting membrane potential and increased frequency of miniature excitatory postsynaptic currents (mEPSCs). Finally, TrkB-ICD overexpression was associated with the upregulation of genes involved in (i) neuronal survival, growth and differentiation; (ii) neuronal cytoarchitecture and spine morphology; (iii) neurodegenerative processes, including AD; and (iv) synaptic transmission and plasticity. Overall, these results show that TrkB-ICD overexpression causes dendritic spine loss, alters excitatory synaptic transmission and causes transcriptome-wide changes, namely in genes coding for proteins involved in synaptic processes.

ORGANISM(S): Rattus norvegicus

PROVIDER: GSE271487 | GEO | 2024/07/30

REPOSITORIES: GEO

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Project description:Background: TrkB-T1 is a BDNF receptor lacking a tyrosine kinase domain that is highly expressed in astrocytes and regulates BDNF-evoked calcium transients. Previous studies indicate that downregulation of TrkB-T1 in frontal cortex may be involved in neurobiological processes underlying suicide. Methods: In a microarray screening study (N=8), we interrogated all known microRNA in the frontal cortex of suicide completers with low expression of TrkB-T1 and normal controls. These findings were validated and followed up in a larger sample of cases and controls (N=55) Functional analyses included microRNA silencing, microRNA overexpression and luciferase assays to investigate specificity and to validate interactions between differentially expressed microRNA and TrkB-T1 Results: microRNAs Hsa-miR-185* and Hsa-miR-491-3p were upregulated in suicide completers with low expression of TrkB.T1 (Pnominal: 9.10-5 and 1.8.10-4 respectively; FDR-corrected p=0.031). Bioinformatic analyses revealed five putative binding sites for the DiGeorge syndrome linked microRNA Hsa-miR-185*in the 3M-bM-^@M-^YUTR of TrkB-T1, but none for Hsa-miR-491-3P. The increase of Hsa-miR-185* in frontal cortex of suicide completers was validated then confirmed in a larger, randomly selected group of suicide completers, where an inverse correlation between Hsa-miR-185* and TrkB-T1 expression was observed ( R=-0.404; p=0.002). Silencing and overexpression studies performed in human cell lines confirmed the inverse relationship between hsa-mir-185* and trkB-T1 expression. Luciferase assays demonstrated that Hsa-miR-185* binds to sequences in the 3M-bM-^@M-^YUTR of TrkB-T1. Conclusion: These results suggest that an increase of Hsa-miR-185* expression levels regulates, at least in part, the TrkB-T1 decrease observed in the frontal cortex of suicide completers and further implicate the 3MB 22q11 region in psychopathology. The microarray analysis consists in to compare the microRNA profile of four suicide completers with low TrkB-T1 expression level and four controls. Each RNA extract was labeled with Hy3 and hybridyzed with a reference sample labeled with Hy5. The reference sample was a pool of the eight RNA samples

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Effects of TrkB-ICD overexpression on the morphology, activity and transcriptome of cultured primary cortical neurons

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