The Study On The Expression Pattern And Function Of Nrf2 In Early Embryonic Development Of Xenopus Tropical

Nrf2?nuclear factor erythrocyte 2 related factor 2?belongs to the CNC?Cap'-N'-Collar?transcription factor family,which binds to a specific cis-acting element ARE?antioxidant response elements?thus transactivating its downstream genes.It suggests that Nrf2transcriptionally regulates more than 600 genes that are largely of antioxidant enzymes,phase II detoxification enzymes and heat shock protein.Numerous studies have suggested Nrf2 as a key regulator in oxidative stress,which plays a crucial role in stress resistance,cellular protection and anti-aging.However,increasing studies have found that excessive activation of Nrf2 causes mice postnatal lethality,stem cell over-differentiation and exhaustion,and renal maldevelopment.It indicates that Nrf2 not only regulates cell protection-related genes to maintain homeostasis,but also participates in cell fate decision hence modulating growth and development.So far,it remains largely equivocal that the role of Nrf2 in early embryonic development and the underlying mechanisms as well.The Xenopus tropical was utilized as a model animal.Firstly,we used qPCR and whole embryo in situ hybridization to reveal the spatiotemporal expression patterns of the Nrf2 in the early embryonic developing process of Xenopus tropical.Secondly,we over-expressed the Nrf2 by microinjection of the Nrf2 mRNA to study the roles of the Nrf2on cell behavior,organ primordium determination and embryonic development.Finally,we explored the network of the Nrf2 that modulated the embryonic development through the RNA-Sequencing and bioinformatics analysis.The results showed that the expression of Nrf2 was throughout the whole development history of Xenopus tropicalis early embryos,mainly expressed in the animal poles during cleavage,mulberry and blastocyst stages,weakly expressed around the embryonic foramen in the gastrula,but the expression level droped to the lowest level;the expression level of Nrf2 began to rise in the neuroembryonic stage and significantly expressed around nerve notochord,and then expressed in nervous system regions head and spine in large quantities in the late caudate stage.More interestingly,we found that the expression of Nrf2 dropped sharply to the lowest level in the gastrula.But it is the key stage in the embryonic development process,where embryonic differentiation,Subsequently,we measured the antioxidant index of early embryos and found that the embryos were in the most sensitive state in the gastrula.So what role does Nrf2 plays at this stage?Overexpression of Nrf2 by microinjection revealed abnormal embryo development and specific phenotype.The main manifestations are:abnormal closure of the blastus in the gastrula,failure of the neural tube in the nerve stage,bending of the spine in the tail period,small eyes in the temporal stage,opacity of the lens and widening of the cloaca.Subsequently,transcriptome studies on gastrula and neuroblasts revealed that after overexpression of Nrf2,the genes involved in germ layer differentiation,body axis establishment and primordia formation were significantly down-regulated during the gut stage;while the embryonic stage,overexpressing Nrf2 It significantly inhibits genes related to neural tube and neural ridge development,and related genes such as cilia and cell movement.Further analysis of the KEGG signaling pathway revealed that Nrf2 in embryos affected many signaling pathways.It mainly includes cell adhesion,oxidative phosphorylation,Ca²⁺,Wnt and Hedgehog signaling pathways.Therefore,the developmental abnormalities caused by overexpression of Nrf2 in embryos may be due to down-regulation of these development-related signaling pathways.In summary,this study found that Nrf2 is a maternal gene that expresses throughout the entire embryonic developmental history and participates in the development of the nervous system.It plays a key role in embryonic early stage germ layer differentiation and cell fate determination.In this study,we have a preliminary view of the expression pattern and function of Nrf2 in embryonic development.Our results provide a new perspective for understanding the mechanism of action of redox signals in embryonic development.