Abstract：To study the expression of microRNA (miRNA) during the early stages of sex differentiation in chicken embryo, and investigate the effect of miRNA on the early development of chicken gonad, six miRNAs (including two chicken novel miRNAs, miR-551b and miR-612) with sexual differential expression were selected based on the results of miRNA chips of chicken (Gallus gallus) embryonic gonads at 3.5~6.5 d and studied by semiquantitative RT-PCR through RNA tailing and primer extension, following validating stem-loop precursor structures of new miRNAs. The results of RNA folding showed that predictive chicken miR-612 and miR-551b possessed stem-loop precursor structures. Semiquantitative results showed the expression of all of the six miRNAs appeared sexual different with varying degrees. Except for 4.5 d, the expression of gga-miR-612 and gga-miR-1456 were higher in females than that in males at other tested stages. The level of gga-miR-551b expression was significantly higher than that in male chicken embryo at 4.5~6.5 d (P<0.05). gga-miR-126 expressed at lower level in female gonads than that in male at 3.5 and 6.5 d, and reversed at 4.5 and 5.5 d. The expression level of gga-miR-1599 was higher in males at all tested stages with significant level at 4.5 d (P<0.01), which was opposite with the expression of gga-miR-10b. Based on the expression results, it is speculated that gga-miR-551b and gga-miR-1599 should have effected on the early process of goand development in chicken embryo.
