Identification And Characterization Of The MiRNA Transcriptome Of Ovis Aries

microRNAs (miRNAs) are a class of endogenously small noncoding RNAs that are about22nucleotides (nt) in length. miRNAs are extensively present in various kinds of animals, plants, andviruses; they mainly cause specific genes to become silent through complementary base pairing with thetarget gene’s3’-untranslation regions (3’-UTR) of mRNAs.Ovis aries (sheep) is of both Biological value and Economic value, but Ovis aries miRNA researchis seriously lagging behind. Texel sheep are typically “double-muscled” sheep, while Ujumqin sheep arethe native fleshy-fat sheep. The two sheep breeds represent phenotypic extremes and are thereforeappropriate animal models for the research of Ovis aries growth and development.This study collected eight developmental stages samples: the longissimus dorsi muscles of Texeland Ujumqin fetuses at70,85,100,120, and135days, and the longissimus dorsi muscles of Ujumqinlambs at0(birth),35, and70d. Texel and Ujumqin libraries were separately subjected to Solexa deepsequencing. We used the ACGT101-miR v4.2and bioinformatics to analyze the sequence data. The mainresults are as follows:(1)35,700,772raw reads were obtained overall from the two miRNA sequencing libraries,corresponding34,964,457mappable reads.(2) The length distribution of miRNAs was mainly20~24nt, and peaked at22nt. miRNAs weremainly present as isomiRNAs.(3) Seven kinds of miRNAs were identified. The list of miRNAs was extended to2,319. Themammalian conserved, Ovis aries known, and predictied candidate miRNAs were1,103,96, and1,216,respectively.(4) Eight kinds of let-7miRNAs were identified, and had the same seed sequences (5’-GAGGTA-3’)with other12mammalian let-7miRNAs.(5) Other researchs discovered181Ovis aries miRNAs, among them,100miRNAs (55.25%) wereidentical to our sequenced miRNAs.(6) This study constructed the Ovis aries miRNAs genome map firstly.1,879miRNAs were mappedto2,436genome locations, and141miRNAs were mapped to150locations on the X chromosome.(7) The Texel and Ujumqin miRNA libraries were obtained16,532,850and19,167,922raw reads,then identified1,601and1,694miRNAs, respectively. Among those,89miRNAs were differentiallyexpressed, and10miRNAs were significant differentially expressed.(8) The TargetScan software predicted8,737target genes of those89miRNAs.(9) The quantitative real time PCR (qPCR) experiments verified those significant differentiallyexpressed10miRNAs in the two sheep breeds.The discovery and identification of Ovis aries miRNAs will further promote the study of miRNAfunctions and gene regulatory mechanisms.