The Effect And Mechanism Of MARVELD1 On Neuronal Radial Migration

The establishment of functional neuronal connectivity depends on the neuronal migration and the accurate positioning of neurons in the developing brain.Abnormal neuronal migration can trigger neuronal maturation defects and apoptosis.During neuronal development,there is a strict space-time specificity process for cell migration and differentiation.When neuronal migration is confused,neurons can not reach the correct place in specific development time point.Thus a series of problems arise,such as neuronal localization and maturation abnormality.These abnormalities eventually lead to neuronal dysfunction and behavior abnormality.MARVELD1 is a MARVEL domain-containing protein expressed in the cell nucleus.MARVELD1 regulates the balance of ITGB1 and ITGB4 through down-regulating ITGB1 and up-regulating ITGB4 in epithelial cells.MARVELD1 gene and its protein are highly conserved in human,mice and apes.So it may play an important role in mammalian growth and development.MARVELD1 is highly expressed in the central nervous system of the mouse embryo,suggesting that MARVELD1 plays a vital role in the normal brain development.Thus,MARVELD1knockout mouse was performed to study the role of MARVELD1 in the brain in this study.In this study,motor and cognitive function of MARVELD1 knockout mice（KO mice）was detected through rotarod test,treadmill assay,gait analysis and morris water maze task.We found that MARVELD1 knockout mice displayed motor and cognitive function abnormalities.Meanwhile,the radiant paw withdrawal test showed that sensory behavioural dysfunctions were also found in MARVELD1 knockout mice.These behavioral abnormalities began in 6-8 week old MARVELD1 knockout mice and sustained in 10 month old mice.Considering the behavioral abnormalities in MARVELD1 knockout mice,neuronal status was analyzed in both cerebral cortex and cerebellum of MARVELD1 knockout mice using HE staining,immunohistochemical technique,TUNEL staining and transmission electron microscopy.The depletion of MARVELD1 led to neuronal apoptosis in both cerebral cortex and cerebellum.Neurons showed late apoptosis and the number of neural synapses was less in the cerebral cortical of 10 month MARVELD1 knockout mice.The dendrites of Purkinje cells were notably sparse and shorter in MARVELD1 knockout cerebellum.The abnormalities in both cerebral cortex and cerebellum of MARVELD1 knockout mice began in 4 week old MARVELD1knockout mice.Then,the study used technologies of HE staining,immunofluorescence,immunohistochemistry and Brdu labeling to study the morphological changes in cerebral cortex and cerebellum of MARVELD1 knockout mice.Disorder of neuronal arrangement was found in both cerebral cortex and cerebellum of MARVELD1knockout mice.Furthermore,there were abnormalities for radial migration of granular cells and the position of Purkinje cells in cerebellum.Based on the consideration that the cerebellum is a well model to study the origin of migration deficits,we focused on the cerebellum to explore the migrating process for further research.Based on the results above,Nestin-cre/MARVELD1^fl/fl mice and GFAP-cre/MARVELD1^fl/fl mice were generated for further study.The Nestin-cre/MARVELD1^fl/fl mice displayed the same disorganization of the cerebellum laminar layers as the MARVELD1 knockout mice.The results from GFAP-cre/MARVELD1^fl/fl mice revealed that the dislocation of granule cells and the defects of Purkinje cells were derived from abnormity of Bergmann glial fibres instead of neurons.Moreover,the study explored the molecular mechanism of neuronal radial migrating regulation from MARVELD1 during brain development through western blot,RT-PCR and immunofluorescence experiments.MARVELD1 depletion led to activation of ITGB1/FAK signaling pathway in cerebellum.The inhibition of the MARVELD1/ITGB1/FAK signaling pathway in knockout mice could give rise to the defects of neuron migration in vitro.Our findings revealed that MARVELD1 regulated neuron migration by mediating the formation of glial fibers and the ITGB1/FAK signaling pathway,and that depletion of MARVELD1 during mouse brain development led to the abnormity of motor and cognition.This study interprets the role and the molecular regulation mechanism of MARVELD1 in mice brain development.So it provides new evidence for the function of MARVELD1 in murine brain.Through this study,the molecular basis of neuronal cell migration and maturation in mice brain could be known.It also reveals the new regulatory mechanism that affects cognitive function of mice.Thus,this study deepens our understanding of MARVELD1 and brain development.