中文摘要：

microRNA（miRNA）是一类内源性的非编码RNA,广泛参与细胞的生长发育、分化、增殖和凋亡等生物学过程.为了研究miR-let-7a对猪（Susscrofa）甲状腺的生长发育及甲状腺细胞凋亡的调控作用,本研究利用免疫荧光技术鉴定了大白猪的甲状腺组织及体外培养的甲状腺细胞,利用实时荧光定量PCR（qRT-PCR）检测了miR-let-7a在不同生长阶段大白猪甲状腺组织中的表达量变化,通过转染miR-let-7a mimics并利用流式细胞术检测了转染组与未转染组的甲状腺细胞凋亡率的差异性,同时预测了miR-let-7a与细胞凋亡相关基因的靶向关系.结果发现,甲状腺组织和细胞中的甲状腺球蛋白（thyroglobulin,TG）发出绿色荧光,表明体外培养的甲状腺细胞功能正常.qRT-PCR结果显示,胚胎期随着胚龄的增加,miR-let-7a表达量逐渐增加.出生后miR-let-7a表达量下降,于60日龄达生长期最小值,之后有所上升,至90日龄后其表达量再次下降,120日龄后随日龄的增加let-7a表达量呈现逐渐增加的趋势.凋亡结果发现,和对照组相比,转染组细胞凋亡率明显升高（P＜0.05）.根据研究结果推测,miR-let-7a的表达直接或间接影响了甲状腺细胞凋亡的调控过程.研究结果为深入研究猪甲状腺miR-let-7a的功能机制提供了有益的线索.

英文摘要：

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-Ta 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-Ta 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 oeriod, 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.