Screening And Functional Identification Of Sexual Dimorphism In Amphioxus Branchiostoma Japonicum

Amphioxus, a cephalochordate, is traditionally considered as the closestrelative to the ancestor of ancient vertebrates．For the unique evolutionary position,simple morphology structure and essential features of vertebrate，amphioxus has beenregarded as excellent model to study the origin of evolution and gonad development inhigher vertebrates．MicroRNAs (miRNAs),~22nucleotides (nt) in length, are a new class ofnon-coding small RNAs in genomes, which play a key role by regulating protein-codinggene expression in a sequence-specific manner for cleavage or translational repression.Studying of sexual dimorphism miRNAs to lower and simpler Cepholochordata such asamphioxus, will contribute to a better study of molecular mechanism of higherorganisms’gonad development.In this study, we used amphioxus Branchiostoma japonicum organizations andzebrafish as materials and amphioxus testis and ovary miRNA array as base to studyexpression and function of miRNA. From microarray results, miR-01，miR-02，miR-03and miR-04were screened,which were abundantly expressed in testis.The expression levels of4miRNAs were analyzed by real time quantitativeRT-PCR at amphioxus gonads to verify the result of array hybridization. The resultindicated that these miRNAs were consistent with array analyzed.In this study, the using of kop-GFN transgenic fish system, fluorescentlylabeled germ cells of zebrafish. Then, the lower expression levels of miRNA to analyzethe impact of zebrafish germ cells by injecting antisense-miRNA. The result displayedthat loss of miR-04leaded to mislocalized PGCs. In addition, lower expression ofmiR-04delayed the zebrafish gonad development, but other miRNA had no effect ongonadal development of the zebrafish.Amphioxus was the ideal model of the vertebrate evolutionary biology anddevelopmental biology study, and miRNA played an important role in evolutionarydevelopment as an important class of gene regulatory factors. Screening and functionstudying of miRNA in lower amphioxus will contribute to a better understanding of the molecular mechanism of sex determination, germ cell tumors, fertility disorders andother diseases in the higher vertebrates. Moreover, a number of drugs will be inventedto improve the quality of human life, and ultimately bring about huge economic andsocial benefits.