title: Changes in circulating microRNA levels can be identified as early as day 8 of pregnancy in cattle.
abstract: Poor reproductive performance remains a major issue in the dairy industry, with low conception rates having a significant impact on milk production through extended calving intervals. A major limiting factor is the lack of reliable methods for early pregnancy diagnosis. Identification of animals within a herd that fail to conceive within 3 weeks after insemination would allow early re-insemination and shorten calving intervals. In a previous study, we found an increase in plasma miR-26a levels in Day 16-pregnant relative to non-pregnant heifers, however changes in miRNA levels that early during pregnancy were very small which likely prevented the identification of robust biomarkers. In this study, we extended our analyses to a wider interval during pregnancy (Days 8 to 60, n = 11 heifers) with the rationale that this may facilitate the identification of additional early pregnancy miRNA biomarkers. Using small RNA sequencing we identified a total of 77 miRNAs that were differentially expressed on Day 60 relative to Day 0 of pregnancy. We selected 14 miRNAs for validation by RT-qPCR and confirmed significant differences in the expression of let-7f, let-7c, miR-30c, miR-101, miR-26a, miR-205 and miR-143 between Days 0 and 60. RT-qPCR profiling throughout Days 0, 8, 16 and 60 of pregnancy showed a distinct increase in circulating levels of miR-26a (3.1-fold, P = 0.046) as early as Day 8 of pregnancy. In summary, in contrast to earlier stages of pregnancy (≤ Day 24), marked differences in the levels of multiple miRNAs can be detected in circulation by Day 60 in cattle. Retrospective analyses showed miR-26a levels to be increased in circulation as early as Day 8, sooner than previously reported in any species, suggesting a biological role for this miRNA in the very early events of pregnancy.
authors.affiliation: The Roslin Institute and R(D)SVS, University of Edinburgh, Roslin, United Kingdom.
authors.forename: Jason
authors.initials: J
authors.lastname: Ioannidis
authors.affiliation: The Roslin Institute and R(D)SVS, University of Edinburgh, Roslin, United Kingdom.
authors.forename: F Xavier
authors.identifier: http://orcid.org/0000-0002-0331-2996
authors.initials: FX
authors.lastname: Donadeu
mesh_terms: D000818:Animals; D002417:Cattle / Q000097:blood* / Q000235:genetics; D005260:Female; D035683:MicroRNAs / Q000097:blood* / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011247:Pregnancy; D011258:Pregnancy Tests / Q000662:veterinary; D011270:Pregnancy, Animal / Q000097:blood*
chemical_list: D035683:MicroRNAs