Abstract：microRNA (miRNA) is a class of endogenous and noncoding RNA, which involves in many physiological processes including cell growth, development, differentiation, proliferation and apoptosis. In order to study the regulation effect of miR-let-7a on growth and development in thyroid, we identified the thyroid tissue and culuture cells in vitro of Yorkshire pig(Sus scrofa) by immunofluorescence technique and detected the expression of miR-let-7a in various growth stages in thyroid of Yorkshire pig by quantitative Real-time PCR(qRT-PCR). To study the effect of miR-let-7a on apoptosis of thyroid cells, miR-let-7a transfected mimics cells were detected to determine the differences of thyroid cell apoptosis rates between the experimental and control groups with Flow Cytometry, and predicted that the target genes of miR-let-7a were related to cell apoptosis. The results showed that thyroglobulin (TG) in thyroid tissue and cells glowed green fluorescence after identification which proved thyroid cells in vitro normal function. In the embryonic period , the expression of miR-let-7a increased gradually with the rise of embryo age. In the growth period, the expression reached the minimum at the 60th day and then increased, but after the 90th day it decreased again and lasted to the 120th day and then increased slowly. Compared with control group, the apoptosis rate of transfected group significantly increased (P＜0.05). In conclusion, suggested that the changes in miR-let-7a expression might affect the regulation on thyroid cell apoptosis directly or indirectly. The study provides useful clues for further research on the functional mechanism of miR-let-7a in pigs.
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