Role Of Inwardly Rectifying Potassium Channel Kir4.1 In Oligodendrocyte Development And Myelin Formation

Oligodendrocyte(OL) are the myelin forming cells of the central nervous system(CNS). It has a very important role in the formation of the myelin sheath and the transmission of the nerve information. Long term studies clearly show that oligodendrocyte dysplasia, demyelination and disorder of the myelin sheath regeneration involved in many central nervous system diseases' pathophysiological process, such as multiple sclerosis(MS), optic neuritis, amyotrophic lateral sclerosis, schizophrenia and depression. New research shows that inwardly rectifying potassium channel 4.1(Kir4.1) have an abnormal expression in the lesion area of MS patients. Kir4.1 channels are widely distributed in a variety of organizations and it was given the name because the relationship between the voltage and current of the channel has the characteristics of inward rectifier. Kir4.1 channel plays a very important role in regulating the excitability of nerve, electrolyte balance and normal nerve function, but it is still not clear whether it is involved in the abnormal of myelination and disease of demyelination or not. OL is derived from oligodendrocyte precursor cell(OPC). At present, there is no report about the role of Kir4.1 in the development of OL and the formation of myelin sheath.Our research aims at whether Kir4.1 is involved in the development of central nervous system myelin sheath. Our experimental data show that Kir4.1 was expressed in both OPC and OL and the level of its expression was significantly increased when OPC was induced into OL. When applicating the Kir4.1 specific blocking agent desipramine(DES), The fluorescence signal of myelin basic protein(MBP) significantly decreased and the quantity of MBP positive cells became less than control. It suggested that blockage of Kir4.1 will hinder the differentiation of OPCs. In addition, development of optic nerve myelin sheath abnormalities was found in the mice with oligodendrocyte lineage specific knockdown of Kir4.1 channels. It indicate that knockdown of Kir4.1 in the oligodendrocyte lineage leads to myelin defects. These data suggest that Kir4.1 is an important role in the development of oligodendrocyte and the formation of myelin. Objective:To determine whether Kir4.1 plays an important role in the development of oligodendrocyte and formation of the myelin sheath. Methods:1.Using Western blot and immunohistochemistry to detect the expression of Kir4.1 and MBP in different stages of OPC differentiation.2.The expression of MBP was detected by Western blot after blocking Kir4.1 channel 96 h at different stages of OPC differentiation using Kir4.1 specific blockage desipramine.3.Using Kir4.1 knock out mice hybrid with oligodendrocyte lineage Cre mice to build genetic modification of mouse strain Olig1-Cre with specific knock out of Kir4.1 channel in the oligodendrocyte lineage. According to the morphological changes by chromium cyanide R staining and electron microscope technique to detect myelin. To observe the effect of Kir4.1 knockout on the development of OL cells by Confocal microscopy. Using Western blot to detect Kir4.1 knockout mice hippocampus, cerebral cortex and spinal MBP expression status. Results:1. The expression of Kir4.1 channel protein and mRNA was increased in OL cells cultured in vitro, and the expression of MBP protein and mRNA in OLs was significantly increased than that in OPCs.2.After desipramine was applicated with OPCs, the expression of MBP was significantly decreased, and the expression of Ki67 and PDGFR were significantly increased.3.Erichrome cyanide R staining and electron microscopy showed that Kir4.1 knockout mice optic nerve myelin dysplasia. Immunofluorescence staining showed that the expression of Olig2 and CC1 decreased in Kir4.1 knockout mice. Blot Western showed that the expression of MBP in hippocampus and cerebral cortex of Kir4.1 knockout mice decreased obviously, and there was no significant change in the expression of MBP in spinal cord. Conclusion :1.The Kir4.1 plays an important role in the development of OL.2.Blocking Kir4.1 can inhibit the differentiation of OPC.3.Dysfunction of Kir4.1 affects the myelin formation in the CNS.