title: A mental retardation gene, motopsin/neurotrypsin/prss12, modulates hippocampal function and social interaction.
abstract: Motopsin is a mosaic serine protease secreted from neuronal cells in various brain regions, including the hippocampus. The loss of motopsin function causes nonsyndromic mental retardation in humans and impairs long-term memory formation in Drosophila. To understand motopsin's function in the mammalian brain, motopsin knockout (KO) mice were generated. Motopsin KO mice did not have significant deficits in memory formation, as tested using the Morris water maze, passive avoidance and Y-maze tests. A social recognition test showed that the motopsin KO mice had the ability to recognize two stimulator mice, suggesting normal social memory. In a social novelty test, motopsin KO mice spent a longer time investigating a familiar mouse than wild-type (WT) mice did. In a resident-intruder test, motopsin KO mice showed prolonged social interaction as compared with WT mice. Consistent with the behavioral deficit, spine density was significantly decreased on apical dendrites, but not on basal dendrites, of hippocampal pyramidal neurons of motopsin KO mice. In contrast, pyramidal neurons at the cingulate cortex showed normal spine density. Spatial learning and social interaction induced the phosphorylation of cAMP-responsive element-binding protein (CREB) in hippocampal neurons of WT mice, whereas the phosphorylation of CREB was markedly decreased in mutant mouse brains. Our results indicate that an extracellular protease, motopsin, preferentially affects social behaviors, and modulates the functions of hippocampal neurons.
authors.affiliation: Department of Neurobiology and Anatomy, Kochi Medical School, Okoh, Nankoku, Japan. smitsui@kochi-u.ac.jp
authors.forename: Shinichi
authors.initials: S
authors.lastname: Mitsui
authors.forename: Yoji
authors.initials: Y
authors.lastname: Osako
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Yokoi
authors.forename: Mai T
authors.initials: MT
authors.lastname: Dang
authors.forename: Kazunari
authors.initials: K
authors.lastname: Yuri
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Li
authors.forename: Nozomi
authors.initials: N
authors.lastname: Yamaguchi
mesh_terms: D000818:Animals; D001007:Anxiety / Q000235:genetics / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D003712:Dendrites / Q000502:physiology; D049229:Dendritic Spines / Q000502:physiology; D005106:Exploratory Behavior / Q000502:physiology; D006179:Gyrus Cinguli / Q000166:cytology / Q000502:physiology; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D007858:Learning / Q000502:physiology; D008297:Male; D008568:Memory / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009483:Neuropsychological Tests; D017966:Pyramidal Cells / Q000166:cytology / Q000502:physiology*; D021641:Recognition, Psychology / Q000502:physiology; D012697:Serine Endopeptidases / Q000235:genetics* / Q000378:metabolism*; D012919:Social Behavior; D013028:Space Perception / Q000502:physiology
chemical_list: C492004:Creb1 protein, mouse; D017362:Cyclic AMP Response Element-Binding Protein; D012697:Serine Endopeptidases; C108493:neurotrypsin