Different expressing of microRNAs in mammary gland tissue of jinhua and yorkshire pig breeds on postpartum 21 days | 金华猪和大约克猪分娩后21 d乳腺microRNAs的预测和差异研究

Chinese. microRNAs(miRNAs)是一类单链小RNAs，是重要的基因表达调控因子，通过与靶基因的3'UTR序列互补来调控基因的表达。鉴定乳腺组织的miRNAs及其靶基因，对揭示miRNA在乳腺组织基因调控中的作用十分重要。本研究分别从分娩后21 d金华和大约克母猪的乳腺组织中提取小RNA并构建各自的cDNA文库，通过Illumina Genome Analyzer Ⅱx测序平台对它们进行高通量深度测序。将测序初始序列经过序列类型、长度、丰度的筛选得到比对序列，然后与已有的miRNA数据库、Genome和EST数据库进行比对。将两个猪种检测到的miRNA进行品种间差异性比较，并在差异性结果中选择相对丰度较高的前10个miRNA对其进行生物信息学分析。结果发现：金华猪乳腺组织的比对序列有9 672 024条，大约克猪6 946 905条；共检测到金华猪单一序列miRNA有848个，大约克猪683个；金华猪预测的新单一序列miRNA有369个，大约克猪231个；两个猪种间差异显著的miRNA有288个(P0.01)；相对丰度较高的前10个miRNA的靶基因有1 829个，这些靶基因主要参与了抗原加工和呈递、Ⅰ型糖尿病、缝隙连接与精氨酸和脯氨酸代谢、同种异体移植排斥等代谢途径。本研究充实了猪miRNA数据库，同时为研究猪乳腺中miRNA的功能和调控机制提供了依据。

English. microRNAs(miRNAs) is a class of single-strand small RNAs that regulate gene expression by binding to complementary sequences in the 3' untranslated region(3'UTR) of target mRNAs. In a sense, identification of miRNAs and their targets in mammary gland tissue is essential to proclaim the function of miRNAs on gene expression and regulation. In the present study, small RNAs were extracted from porcine mammary gland tissue of Jinhua and Yorkshire breed respectively and used to construct a cDNA library. Then it was sequenced by Illumina Genome AnalyzerⅡx. Mappable sequences were obtained from raw sequences which filtered junk, short, simple, low copy and certain known types of RNA sequences. BLASTNs were performed between miRNABase Genome, EST database and mappable sequences. Different miRNAs detected between two pig breeds were conducted, and top ten abundance of miRNAs were selected for further bioinformatics analysis. The results showed that the reads of mappable sequence was 9 672 024 in the mammary gland tissue of Jinhua pig and 6 946 905 in Yorkshire pig, while the number of unique miRNA detected in Jinhua pig was 848 and 683 in Yorkshire pig. Moreover, 369 and 231potential novel unique miRNAs in Jinhua and Yorkshire pigs were discovered, respectively. Totally 288 miRNAs had significant difference between Jinhua and Yorkshire pigs(P0.01), and 1 829 targets in accordance with top ten abundance of miRNAs were also revealed. These targets were primarily involved in many pathways such as antigen processing and presentation, typeⅠdiabetes mellitus, gap junction, allograft rejection and so on, suggest that these miRNAs have widely roles in physiological metabolism processing of mammary gland. Our study enriches the porcine miRNABase and provides a basis for researching the function and the regulated mechanism of miRNA in mammary gland tissue.