Identification And Differential Expression Analysis Of MicroRNAs In Heart And Lung Tissues Between Yak And Cattle

Yak is a unique livestock living in the Qinghai-Tibet Plateau and adjacent areas,with altitude of 2500 m?6000 m.Yak have evolved some unequal anatomical and physiological traits to equip the extreme circumstances at high altitude,including larger lungs and hearts,blunted hypoxic pulmonary vasoconstriction,strong environmental sense and high energy metabolism.MicroRNA(miRNA)is a class of endogenous short non-coding RNA that post-transcriptionally modulate gene expression through either translational repression or mRNA degradation.Recent studies identified a large amount of hypoxia-induced miRNAs have widely participate in some biological process,including cell apoptosis and regulation of metabolism.Extensive and in-depth investigations of high altitude adaptation have been carried out at the level of morphology,anatomy,hemodynamics,physiology and genomics,few investigation focused on the role of epigenetics in high altitude adaptation.In this study,we constructed 11 small RNA cDNA libraries of heart and lung tissues in 3 female yaks and 3 female cattle,and performed small RNA sequencing.This study was aimed to investigate whether miRNA was involved in the mechanism of high altitude adaptation,the kind of high altitude-adaptation miRNAs,and the function of these high altitude-adaptation miRNAs.All results are as follows:1 A total of 96.19M(million)raw data was generated from 11 sequencing libraries;with an average of 8.74 M(8.74 ± 3.37 M)in each library.After a series of rigorous filters,total of 84.57 M(88.86 ± 4.87%)clean reads was remained for further analysis,with an average of 7.69 ± 2.68 M in each library.Clean reads comprised most of raw data in each library,with an average percentage of 88.8%.2 Totally,808 unique mature miRNAs were identified in 11 sequencing libraries,generating from 715 pre-miRNAs.Total of 769 mature miRNAs and 660 pre-miRNAs were identified in cattle,in comparison 757 mature miRNAs and 649 pre-miRNAs were identified in yak.Biological replicate showed high consistency with each other,with an average positive correlation up to 0.99.3 In average,top 10 miRNAs occupied the 62%of total miRNA expression.All of top 10 expressed miRNAs in heart tissue were all the same between yak and cattle,and 5 of top 10 expressed miRNAs in lung tissue were shared between yak and cattle,indicating the important roles and strong conservation of highly expressed miRNAs in a particular tissue.4 The differential expression analysi's have identified 90 differentially expressed miRNA in heart tissue between yak and cattle,of which 21 were differentially and highly expressed.The target prediction and functional analysis revealed that target genes of differentially and highly expressed miRNAs are enriched in 19 terms,including insulin signaling pathway,regulation of glucose metabolic process,response to hypoxia,regulation of cellular response to stress,positive regulation of fatty acid oxidation.5 The differential expression analysis have also identified 63 differentially expressed miRNA in lung tissue between yak and cattle,of which 56 were differentially and highly expressed.The target prediction and functional analysis revealed that target genes of differentially and highly expressed miRNA are enriched in 16 terms,including insulin signaling pathway,regulation of glucose metabolic process,response to hypoxia,regulation of cellular response to stress,positive regulation of fatty acid oxidation et al.