Effects Of C-myc Gene On The Development Of Cerebral Cortex Neurons

ObjectiveThe mammalian cerebral cortex,the most complex structure of the nervous system,is responsible for implementing the most complex neural activity.The precise functions of cerebral cortex were realized by proliferation,migration and differentiation of neural progenitor cells(NPCs)according to a defined temporal sequence to form a six layer-specific excitatory neuronal type in the cerebral cortex.There exist many effectors invoving in the development of cerebral cortex neurons,and when abnormality in any step of this process occurs,neurological syndromes may be triggered,such as schizophrenia,autistic disorder and alzheimer disease.C-myc,an oncogene,is one of the members of Myc family that are involved in fundamental cellular processes including proliferation,growth,apoptosis and differentiation.In the brain,knockout of c-myc led to embryonic lethality around midgestation suggesting that myc genes are essential for normal development during the process of organogenesis.Furthermore,acute forebrain specific inactivation of c-myc in vivo apparently decreased the self-renewal activity of NPCs,illustrating an intrinsic requirement for c-myc in NPCs.However,the function of c-myc in the development of cerebral cortex neurons is remains unclear.In this study,we aim to make the problem clear by exploring the effects of c-myc gene on the proliferation,differentiation and migration of neurons in the cerebral cortex.Method1.CAD cells or NPCs were isolated from the lateral ventricle walls of E14.5 ICR mouse which was electroporated with specific si RNA or c-myc plasmid.After three days culture,the cells were collected and used to detect the efficiency of si RNA or c-myc plasmid via western blot.2.To inhibit or overexpress c-myc in neural progenitor cells of cerebral cortex,specific si RNA or c-myc plasmid was electroporated into lateral ventricle of E14.5 mice via in utero electroporation.3.The electroporated mice were sacrificed and brains were obtained after electroporated for four days.Some of the brains were used to detect the efficiency of si RNA and c-myc plasmid via western blot,and other brains were sliced into 14?m sections using the cryomicrotome.4.The sections of the electroporated cerebral cortex were stained for Brd U,Tbr2,Cux1 and ??-tubulin respectively,and the percentage of Brd U+GFP+,Tbr2+GFP+,Cux1+GFP+ or ??-tubulin+GFP+ of total GFP+ cells were calculated to explore the influence of c-myc in the proliferation,migration and differentiation of neural progenitor cells in cotical cortex.Results1.c-myc was expressed in neural progenitor cells in cerebral cortex.When specific c-myc si RNA or c-myc plasmid was electroporated to the lateral ventricle walls of E14.5 ICR mouse,the expression level of c-myc in cerebral cortex was decreased or increased accordingly.2.Knocking down c-myc gene of cerebral cortex with si RNA,the percentage of Brd U+GFP+ and Tbr2+GFP+ cells were decreased,and the percentage of Cux1+GFP+ and ??-tubulin +GFP+ cells were increased inversely.3.Overexpressing c-myc with c-myc plasmid,the percentage of Brd U+GFP+and Tbr2+GFP+cells were increased,and the percentage of Cux1+GFP+ and ??-tubulin +GFP+ cells were decreased to the contrary.ConclusionC-myc gene was expressed in neural progenitor cells of cerebral cortex.Disturbing the expression of c-myc in cerebral cortex would impede the proliferation of NPCs in the VZ and the genesis of IPCs in the SVZ,but the differentiation of neural progenitor cell to neuron would be improved obviously.In contrast,improving the overexpression of c-myc in cerebral cortex could promote the proliferation of NPCs in the VZ and the genesis of IPCs in the SVZ,and the differentiation of neural progenitor cell to neuron would be decreased severely.In conclusion,these results conjunctively show that c-myc is crucial in the development of cerebral cortex neurons.