Molecular and behavioral changes associated with adult hippocampus-specific SynGAP1 knockout.
The synaptic Ras/Rap-GTPase-activating protein (SynGAP1) plays a unique role in regulating specific downstream intracellular events in response to N-methyl-D-aspartate receptor (NMDAR) activation. Constitutive heterozygous loss of SynGAP1 disrupts NMDAR-mediated physiological and behavioral processes, but the disruptions might be of developmental origin. Therefore, the precise role of SynGAP1 in the adult brain, including its relative functional significance within specific brain regions, remains unexplored. The present study constitutes the first attempt in achieving adult hippocampal-specific SynGAP1 knockout using the Cre/loxP approach. Here, we report that this manipulation led to a significant numerical increase in both small and large GluA1 and NR1 immunoreactive clusters, many of which were non-opposed to presynaptic terminals. In parallel, the observed marked decline in the amplitude of spontaneous excitatory currents (sEPSCs) and inter-event intervals supported the impression that SynGAP1 loss might facilitate the accumulation of extrasynaptic glutamatergic receptors. In addition, SynGAP1-mediated signaling appears to be critical for the proper integration and survival of newborn neurons. The manipulation impaired reversal learning in the probe test of the water maze and induced a delay-dependent impairment in spatial recognition memory. It did not significantly affect anxiety or reference memory acquisition but induced a substantial elevation in spontaneous locomotor activity in the open field test. Thus, the present study demonstrates the functional significance of SynGAP1 signaling in the adult brain by capturing several changes that are dependent on NMDAR and hippocampal integrity.
Laboratory of Behavioral Neurobiology, Swiss Federal Institute of Technology, CH-8063 Schwerzenbach, Switzerland.
Mary
M
Muhia
Silvia
S
Willadt
Benjamin K
BK
Yee
Joram
J
Feldon
Jean-Charles
JC
Paterna
Severin
S
Schwendener
Kaspar
K
Vogt
Mary B
MB
Kennedy
Irene
I
Knuesel
D000704:Analysis of Variance; D000818:Animals; D001362:Avoidance Learning / Q000502:physiology; D000089622:Doublecortin Domain Proteins; D005786:Gene Expression Regulation / Q000235:genetics; D005822:Genetic Vectors / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics; D006624:Hippocampus / Q000166:cytology* / Q000378:metabolism; D019426:Integrases / Q000235:genetics / Q000378:metabolism; D007859:Learning Disabilities / Q000235:genetics*; D018782:Maze Learning / Q000502:physiology; D008564:Membrane Potentials / Q000235:genetics; D008569:Memory Disorders / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009043:Motor Activity / Q000235:genetics; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009479:Neuropeptides / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011930:Reaction Time / Q000235:genetics; D018091:Receptors, AMPA / Q000235:genetics / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000235:genetics / Q000378:metabolism; D013037:Spatial Behavior / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000235:genetics*; D014161:Transduction, Genetic; D020703:ras GTPase-Activating Proteins / Q000172:deficiency* / Q000378:metabolism
D000089622:Doublecortin Domain Proteins; D049452:Green Fluorescent Proteins; D019426:Integrases; D008869:Microtubule-Associated Proteins; D009479:Neuropeptides; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D020703:ras GTPase-Activating Proteins; C409466:NR1 NMDA receptor; C484512:Syngap1 protein, mouse; C485184:enhanced green fluorescent protein; C045073:Cre recombinase