The Fuction Of Trio Gene In The Development Of Hippocampus And Intelligence In Mice

Background:Acting as a key guanine nucleotide exchange factor with multiple catalytic domains,Trio protein involves in cytoskeleton dynamics regulation and actin remodeling, thus regulates neural cell migration, axonal growth and axonal guidance during nervous system developmental process. Previous research about Trio gene function during mice developmental process has proved that null allele of Trio gene led to embryonic lethality, and Trio null embryos displayed aberrant organization and development defect in several regions of the brain at E18.5, including cerebral cortex and hippocampus. Nestin-Trio-/- mice, in which the Trio gene was deleted specifically in the whole nervous system by Nestin-Cre recombinase system, displayed low survival rate and most of Nestin-Trio-/-mice died after birth. At last, all Nestin-Trio-/-mice died before reaching adult stage. Survived Nestin-Trio-/-mice displayed severe phenotypes, including ataxia in behaivour test and multiple developmental defects of brain in nervous system histological research. Nestin-Trio-/-mice were not able to reach adult stage, which hinders further research on Trio gene function during adult mice developmental process because of animal material absence. To solve this problem, we generated EMX1-Trio-/-mice by crossing Trio-Floxedmice with EMX1-Cremice. Trio gene function during EMX1-Trio-/- mice developmental process was revealed via different experimental method, including molecule techonology, histological analysis and animal behavior test, etc.Object:Our goal is to explore Trio gene function in mice brain developmental process via EMX1-Trio-/- mice generation. Behaviour test was performed for revealing intelligence interruption of these EMX1-Trio-/-mice.Methods:We used EMX1-Cre mice to cross with Trio-Floxed mice, thus generated EMX1-Trio-/- mice. EMX1-Cre recombinase specifically deletes Trio gene fragments with double loxP sites insertion in cerebral cortex and hippocampus region. These generated knockout mice will survive to adult stage and be exposed to behavior test for their intelligence evaluation. Besides behavior test, we also used histological section, H&E staining, Western Blot and other experimental methods to explore EMX1-Trio-/- mice brain development after Trio gene deletion. Histological section analysis and behavior test result are combined to reveal Trio gene function in mice brain developmental process and intelligence formation.Results:For EMX1-Cre transgenice mice, Cre recombinases are expressed specifically in cerebral cortex and hippocampus region, thus delete Floxed-Trio gene fragments in those tissues. EMX1-Trid-/- mice can survive to adulthood stage, which ensures the animal material for adult mice development research. Research on EMXl-Trio-/- mice showed that Trio gene deletion in cerebral cortex and hippocampus region via EMXl-Cre recombinases resulted in severe phenotypes, including smaller brains size, hippocampus structure defect,twisted structure of both dentate gyrus(DG)and cornu ammonis(CA), etc. In addition, the arrangement of granule cells in adult EMX1-Trio-γ-mice was messy when compared to WT mice. Behavior tests of adult EMX1-Trio-/-mice proved that specific Trio gene deletion via EMX1-Cre recombinases resulted in hippocampal-dependent intelligence lesion. In addition, mice morphology is also related with Trio gene regulation:body weight of EMXl-Trio-/- mice was significantly decreased when compared to WT mice before P30 days. After P30 days, the body weight of EMX1-Trio-/- mice catched up with the body weight of WT mice. Altough the body weight could be compensated as time goes on, the brain weight of EMX1-Trio-/- mice was always decreased when compared with WT mice and not able to catch up with WT mice.Conclusions:Trio gene regulates adult mice intelligence via affecting hippocampus development during brain neurogenesis. Because of the irreplaceable role of Trio gene,Trio gene specific deletion via EMX1-Cre recombinase led to adult cerebral cortex and hippocampus developmental defect. The development defect of mice brain resulted in brain weight reducing, body weight decreasing and hippocampus structure abnormality. At last, brain abnormality resulted in intelligence lesion in adult EMX1-Trid-/- mice. The intelligence lesion caused food competition failure of EMX1-Trio-/- pups, leading to nutrient deficiency. Body weight decreasing of EMX1-Trio-/- mice during early developmental process resulted from nutrient deficiency. In conclusion, Trio gene plays irreplaceable role in neurogenesis regulation in mice brain and hippocampus development, thus regulates adult mice intelligence.