The Role And Mechanism Of MiR - 124 In Retinal Cell Differentiation Of Xenopus Laevis

The mechanisms of generation and differentiation of nerve cells are the basic scientific questions in developmental biology. What kind offate a cell will have depends on signals the cell received and specific genes expression induced. How to control the directed differentiation of stem cells in vivo is still a problem to be solved.MiRNA is about 22 nucleotides endogenous non-coding RNA small molecules. By degrading the target mRNA or restraining transcription process of mRNA on the basis of complementing with 3’untranslated region of target mRNA sequence miRNA could decrease expression of gene. MiRNAs regulate development of animal embryos. Approximate 50% of mammalian miRNA exist in the adult brain and the developing nervous system, adjusting the development and differentiation of embryos and adult neural stem cells. Research on the function of miRNA in neuron system could contribute to a comprehensive analysis of the net of neurodevelopmental molecular regulatory. And also provide important clues for miRNA-related applications in the treatment of neurological diseases.Mir-124 is a critical molecular for the development of brain and eye. And miR-124 is a loyal miRNA that expressing in the nervous system. Our previous article reported that mir-124 can regulate early neurogenesis. And a lack of miR-124 in Xenopus could lead to malformation of optic nerve and optic cup. However, whether miR-124 involved in the cell fate determination of retinal cell and the molecular mechanisms underlying are largely unknown.In this study, we have found that miR-124 could affect cell fate determination of retinal bipolar cells and horizontal cells, without significantly affecting on other cells in the retina. MiR-124 overexpression in the retina can lead to lower proportion of retinal bipolar cells and higher proportion of horizontal cells. We found that the expression of the OTX2 protein is reduced, and OTX2 is cell specific molecular markers for bipolar cell. Inhibiting the expression of miR-124 will lead to a increase of ratio of bipolar cell. And the expression of OTX2 is increased. This shows that miR-124 is a critical role on cell fate determination of bipolar cell.Then we found that OTX2 involved in the process of miR-124-mediated cell fate regulation. Our experiments show that miR-124 and Otx2 mRNA 3’non-coding sequence are complementary. This complementarity is conserved among the various vertebrate species. And Otx2 mRNA is capable of restore the effects that caused by miR-124 overexpression. In molecule aspect and organization aspect we have proved that OTX2 may be involved in the process of miR-124-mediated cell fate regulation.