Exploration of microRNAs in porcine milk exosomes.
BACKGROUND
Breast milk contains complex nutrients and facilitates the maturation of various biological systems in infants. Exosomes, membranous vesicles of endocytic origin found in different body fluids such as milk, can mediate intercellular communication. We hypothesized that microRNAs (miRNAs), a class of non-coding small RNAs of 18-25 nt which are known to be packaged in exosomes of human, bovine and porcine milk, may play important roles in the development of piglets.


RESULTS
In this study, exosomes of approximately 100 nm in diameter were isolated from porcine milk through serial centrifugation and ultracentrifugation procedures. Total RNA was extracted from exosomes, and 5S ribosomal RNA was found to be the major RNA component. Solexa sequencing showed a total of 491 miRNAs, including 176 known miRNAs and 315 novel mature miRNAs (representing 366 pre-miRNAs), which were distributed among 30 clusters and 35 families, and two predicted novel miRNAs were verified targeting 3'UTR of IGF-1R by luciferase assay. Interestingly, we observed that three miRNAs (ssc-let-7e, ssc-miR-27a, and ssc-miR-30a) could be generated from miRNA-offset RNAs (moRNAs). The top 10 miRNAs accounted for 74.5% (67,154 counts) of total counts, which were predicted to target 2,333 genes by RNAhybrid software. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses using DAVID bioinformatics resources indicated that the identified miRNAs targeted genes enriched in transcription, immunity and metabolism processes, and 14 of the top 20 miRNAs possibly participate in regulation of the IgA immune network.


CONCLUSIONS
Our findings suggest that porcine milk exosomes contain a large number of miRNAs, which potentially play an important role in information transfer from sow milk to piglets. The predicted miRNAs of porcine milk exosomes in this study provide a basis for future biochemical and biophysical function studies.
Ting
T
Chen
Qian-Yun
QY
Xi
Rui-Song
RS
Ye
Xiao
X
Cheng
Qi-En
QE
Qi
Song-Bo
SB
Wang
Gang
G
Shu
Li-Na
LN
Wang
Xiao-Tong
XT
Zhu
Qing-Yan
QY
Jiang
Guandong Provincial Key Lab of Agro-Animal Genomics And Molecular Breeding, College of Animal Science, ALLTECH-SCAU Animal Nutrition Control Research Alliance, National Engineering Research Center For Breeding Swine Industry, South China Agricultural University, Guangzhou 510642, China. Zhangyl@scau.edu.cn.
Yong-Liang
YL
Zhang
D020413:3' Untranslated Regions; D000818:Animals; D001483:Base Sequence; D016000:Cluster Analysis; D019295:Computational Biology; D055354:Exosomes / Q000235:genetics* / Q000378:metabolism; D059014:High-Throughput Nucleotide Sequencing; D035683:MicroRNAs / Q000737:chemistry / Q000378:metabolism*; D008892:Milk / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017423:Sequence Analysis, RNA; D013552:Swine / Q000235:genetics
D020413:3' Untranslated Regions; D035683:MicroRNAs; D017526:Receptor, IGF Type 1