The Role Of Bmal1 In Neuronal Radial Migration And Axonal Projection Of Embryonic Mouse Cerebral Cortex

The function and plasticity of the brain depend on the complex neural circuit structure that is established during development.The cerebral cortex is very important to advanced cognitive or executive function in the mammalian brain.The development of cerebral cortex requires the coordination of a series of key cascades,including neuronal proliferation,migration,and differentiation.Deficiency in any of these processes can result in different disorders of the nervous system.As an important part of the cortical development process,it is important for neurons to migrate into the appropriate sites within the neocortex and to obtain layer-specific neuronal identity and axon projection.Many molecules or factors are inplied in the regulation of radial migration of neurons during brain development and the extension of axons from the corpus callosum projection neurons to the contralateral hemisphere.The related regulatory mechanisms may play an important role in the formation and evolution of nervous system structure and be involved in the pathogenesis of developmental diseases of the nervous system.The mammalian circadian clock gene Bmal1(Brain And Muscle ARNT-Like 1)is a transcription factor containing a family of bHLH(basic helix-loop-helix)-PAS(PER-ARNT-SIM)domains.It is a core part of the transcription and translation feedback loop of the circadian clock and a key component of the molecular diurnal oscillator.An indispensable component of mammalian circadian pacemaker.However,its expression and related functions in the development of the nervous system have rarely been reported so far.Recent studies have shown that the Bmal1 gene also in regulating the timely entry of progenitor cells into the cell cycle and the number of cell divisions that take place prior to cell-cycle exit.This findings provide a cue for the link between the Bmal1 gene and the neurodevelopment.Here we combined mutiple techniques in developmental biology,molecular biology,tissue cytology and genetics,such as RT-RCR,Real-time PCR,Western blotting and In Utero Electroporation,to explore the expression pattern and functional role of Bmal1 in developing mouse cerebral cortex..We found that the expression of Bmal1 gene was abundant in the developing mouse brain,in an age-dependent expression pattern in different developmental stages,enriching at perinatal stages,and peaking at P3(postnatal day 3).The results suggests that Bmal1 may play a potential role in the development of the brain.Subsequently,we combined In utero electroporation with RNAi technique,and found that down-regulation of Bmal1 impaired neuronal migration,depending the knockdown efficiency of RNAi,with gene dose-dependent effect.Furthermore,we found that reducing the expression level of Bmal1 in the brain dampened the axonal projection in the corpus callosum,indicating the role of Bmal1 in axonal growth in developing brain.These findings will help us to understand the biological function of Bmal1 in developing brain and provide new insights intothe regulatory mechanisms underlying cortical development and the pathogenesis of the relevant disorders.