Altered hippocampal-dependent memory and motor function in neuropilin 2-deficient mice

Semaphorins have an important role in synapse refinement in the mammalian nervous system. The class 3 semaphorin-3F (Sema3F) acting through neuropilin 2/plexin-A3 (Nrp2/PlexA3) holoreceptor complex signals in vivo to restrain apical dendritic spine morphogenesis of cortical pyramidal neurons and hippocampal neurons during postnatal development and mediates excitatory synaptic transmission. Semaphorin signaling has been implicated in the etiology of a number of neurodevelopmental disorders; however, the effects on behavior and mental function of dysregulated Sema3F-Nrp2 signaling have not been fully addressed. The present study is the first behavioral investigation of mice harboring a mutation of the nrp2 gene. Given that loss of Nrp2 signaling alters cortical and hippocampal synaptic organization, we investigated performance of nrp2-deficient mice on learning and sensorimotor function that are known to depend on cortical and hippocampal circuitry. When compared with age-matched controls, nrp2 null mice showed striking impairments in object recognition memory and preference for social novelty. In addition, nrp2(-/-) mice displayed impaired motor function in the rotarod test and in observations of grooming behavior. Exploration of novel olfactory sensory stimuli and nociception were unaffected by the loss of Nrp2. Overall, loss of Nrp2 may induce aberrant processing within hippocampal and corticostriatal networks that may contribute to neurodevelopmental disease mechanisms.