APP-deficient neurons show a subtle differential gene expression pattern: impairment in the expression of the activity-dependent transcription factor, NPAS4.
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1
Université Catholique de Louvain, Institute of NeuroScience/ Pôle de biologie cellulaire et moléculaire (CEMO), Belgium
Introduction
The Amyloid Precursor Protein (APP) plays a key role in the onset and progression of Alzheimer’s disease. An increasing number of evidence, including our work, indicates that APP controls the transcription of genes involved in physio/pathological processes relevant to AD. So far, APP-dependent gene transcription was suggested to be mediated by its intracellular domain (AICD). Unfortunately, target genes, partner proteins and signaling mechanisms are poorly understood, and even an increasing matter of controversy. Our work here is addressing the function of APP based on target gene expression regulation in primary neuron cultures.
Objective
We carried out an unbiased analysis of APP dependent transcriptome. We used neuronal cultures derived from APP+/+ and APP-/- embryos to identify the transcripts (coding and non-coding) controlled by APP upon neuronal differentiation, and further investigate their APP-dependent transcriptional regulation and their involvement in APP physiological function.
Methods
Primary mouse embryonic (E18) cortical neurons from WT or APP -/- were subjected to microarray analysis with GeneChip® Mouse Transcriptome Array 1.0 Affymetrix profiling the expression of coding and non-coding transcripts. RNAs were extracted and reverse-transcribed from 7 days cortical neuron cultures. Candidate genes were re-probed by RT-qPCR and Western blotting in different conditions.
Results
None of the admitted APP/AICD target genes were differentially expressed in APP+/+ vs. APP -/- transcriptome analysis. Only few coding genes showed changes in gene expression profiles (APP+/+ vs. APP-/- neurons), especially for a linear fold change cut-off set at 1,5. Among these, the expression of NPAS4, an activity-dependent transcription factor, seems downregulated in APP -/- neurons. This was confirmed by RT-qPCR and Western blotting. We investigated the use of the CRISPR-Cas9 system against APP in order to acutely delete the APP-expression in order to avoid APLPs redundant compensation we observed in APP-/- background. Preliminary results show that NPAS4 expression is decreased after an “acute” deletion of APP during neuronal maturation in vitro.
Conclusion
APP could modulate gene expression in a very subtle and often masked manner as it was suggested that APP-like proteins can share redundant functions and compensate the loss of APP. We set up a different condition to unravel APP-dependent gene transcription in that process. Our data are in line with those of Aydin D. et al (2011) who observed only a minor to moderate changes in gene expression by comparing adult APP+/+ and APP-/- prefrontal cortices. In line with this idea, APP-/- mice have a mild phenotype. However, we found that an activity-dependent transcription factor, NPAS4, is downregulated in absence of APP during neuronal maturation. We further investigate this regarding the role of APP in synaptic function. NPAS4 is known to tightly regulate inhibitory synapses formation and therefore to play an important role in inhibitory/excitatory neurotransmission homeostasis
Acknowledgements
We thank Mrs Tasiaux Bernadette for the technical support of this work.
This work was supported by "Fond pour la Rechercher dans l'Industrie et l'Agriculture" (FRIA) - FNRS
Keywords:
amyloid precursor protein,
Neurons,
Transcription, Genetic,
Gene Expression Regulation,
Transcription Factors
Conference:
12th National Congress of the Belgian Society for Neuroscience, Gent, Belgium, 22 May - 22 May, 2017.
Presentation Type:
Poster Presentation
Topic:
Neural Excitability, Synapses, and Glia: Cellular Mechanisms
Citation:
Opsomer
R,
Contino
S,
Stanga
S,
Doshina
A,
Pierrot
N,
Dewachter
I,
Octave
J and
Kienlen-Campard
P
(2019). APP-deficient neurons show a subtle differential gene expression pattern: impairment in the expression of the activity-dependent transcription factor, NPAS4..
Front. Neurosci.
Conference Abstract:
12th National Congress of the Belgian Society for Neuroscience.
doi: 10.3389/conf.fnins.2017.94.00024
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Received:
02 May 2017;
Published Online:
25 Jan 2019.
*
Correspondence:
Mr. Rémi Opsomer, Université Catholique de Louvain, Institute of NeuroScience/ Pôle de biologie cellulaire et moléculaire (CEMO), Brussels, Outside the United States and Canada, 1200, Belgium, remi.opsomer@uclouvain.be
Prof. Pascal Kienlen-Campard, Université Catholique de Louvain, Institute of NeuroScience/ Pôle de biologie cellulaire et moléculaire (CEMO), Brussels, Outside the United States and Canada, 1200, Belgium, pascal.kienlen-campard@uclouvain.be