© Fabien LOUSTALOT / Eric KREMER / IGMM / INSERM / CNRS Photothèque
Neurons in the hippocampus of a mouse observed using a fluorescence confocal microscope, then reconstructed in 2D by projecting 34 optical sections onto the Z-plane. The cell nuclei have been marked in blue using immunofluorescence labelling (DAPI). The CAR protein has been marked using two different antibodies, both detected by two fluorescent antibodies of different colours (red and green, hence the colour yellow). The CAR protein is known to be an adenovirus receptor. As this protein is expressed more strongly in the central nervous system (CNS) during development, research scientists have attempted to identify its role in the establishment of neural networks (neurogenesis). They have discovered that CAR is found in the synapse, a key neuronal substructure that enables neurotransmission, and that this protein is chiefly present in the hippocampus. In murine hippocampal neurons in culture, CAR has been located in structures containing proteins that regulate synaptic activity, such as synaptophysin. This protein could influence adult neurogenesis and/or synaptic plasticity. After this, the scientists created a line of mice in which the gene encoding CAR was specifically impaired in cells of neural origin. The results demonstrate that mice that do not express CAR in the central nervous system present a neurogenesis impairment, which can be identified by anxious behaviour and problems with spatial memory. This has oriented research towards Alzheimer’s disease, and it has been shown that CAR expression diminishes during the early and late stages of this disease. Finally, scientists have been able to identify that neuroinflammation could modulate the stability of CAR.