Project description:Low fertility remains a leading cause of poor productivity in dairy cattle. In this context, there is significant interest in developing novel tools for accurate early diagnosis of pregnancy. MicroRNAs (miRNAs) are short RNA molecules which are critically involved in regulating gene expression during both health and disease. MiRNAs have been shown to regulate ovarian function, uterine receptivity, embryonic development and placental function. Circulating miRNAs can provide useful biomarkers of tissue function and disease; importantly, differential miRNA profiles have been linked to pregnancy and preeclampsia in humans. This study sought to establish the potential of circulating miRNAs as biomarkers of early pregnancy in cattle. We applied Illumina small-RNA sequencing to profile miRNAs in plasma samples collected from eight non-pregnant heifers on Days 0, 8 and 16 of the oestrous cycle and 11 heifers on Days 16 and 24 of pregnancy. We sequenced a total of 46 samples and generated 9.2 million miRNA reads per sample. There were no differences in miRNA read abundance between any of the pregnant and non-pregnant time-points (FDRâ>â0.1). As a complementary approach, we analysed sample pools (3-4 samples/pool) corresponding to Days 0, 8 and 16 of the oestrous cycle and Day 24 of pregnancy (nâ=â3 pools/group) using Qiagen PCR arrays. A total of 16 miRNAs were differentially expressed (FDRâ<â0.1) in plasma between pregnant and non-pregnant animals. RT-qPCR validation using the same plasma samples confirmed that miR-26a was differentially upregulated on Day 16 pregnant relative to non-pregnant heifers (1.7-fold; Pâ=â0.043), whereas miR-1249 tended to be upregulated in Day 16 pregnant heifers (1.6-fold; Pâ=â0.081). Further validation in an independent group of heifers confirmed an increase in plasma miR-26a levels during early pregnancy, which was significant only on Day 24 (2.0-fold; Pâ=â0.027). Through genome-wide analyses we have successfully profiled plasma miRNA populations associated with early pregnancy in cattle. We have identified miR-26a as a potential circulating biomarker of early pregnancy. Sequencing of three sequencial samples from each of eight cycling animals (Days 0, 8 and 16, total 24 samples) and two samples from each of 11 pregnant animals (Days 16 and 24, total 22 samples). Main comparisons were between non-pregnant and pregnant groups

Project description:An increase in circulating progesterone (P4) concentrations is associated with increased pregnancy success in beef and dairy cattle. Our objective was to ascertain differential effects of elevated P4 concentrations following conception on endometrial gene expression in beef heifers on Days 5, 7, 13 and 16 of pregnancy, corresponding to the morula, blastocyst, elongation and maternal recognition of pregnancy stages, respectively. Estrus was synchronized in beef heifers (N=263). Two-thirds (N=140) were inseminated (Day 0), and all animals were randomly assigned to one of the following treatments: (i) pregnant, high P4; (ii) pregnant, normal P4; (iii) cycling, high P4; (iv) and cycling, normal P4. All high P4 groups received a P4 release intravaginal device (PRID) on Day 3 post-estrus/mating. Tissue was collected on Days 5, 7, 13 or 16 of the cycle or pregnancy, and pregnancy was confirmed by the presence of an appropriately developed embryo/conceptus. PRID insertion elevated (P<0.05) P4 concentrations from Day 3.5 to 8 compared with untreated animals and conceptus size was larger (P<0.05) in animals with elevated P4 on Days 13 and 16 compared with normal P4. Total RNA was extracted from predominantly intercaruncular endometria from the ipsilateral uterine horn. Samples from individual heifers were selected on the basis of their P4 profiles and gene expression was analyzed using bovine Affymetrix microarrays (N=5 per treatment per time point). Microarray data from analyses using Bioconductor GCRMA and Limma packages were subjected to a modified t-test and P-values were adjusted for multiple testing using the Benjamin and Hochberg false discovery rate method. Differentially expressed genes were selected on the basis of an adjusted P-value of <0.01. There were no detectable differences in gene expression in endometria from pregnant and cyclic heifers on Days 5, 7 and 13 post-estrus, but, the expression of 764 genes was altered due to the presence of the conceptus at maternal recognition of pregnancy (Day 16). On Days 5 and 7, elevated P4 in pregnant heifers, altered the expression of 36 and 124 genes respectively but on Days 13 and 16 there were relatively few DEG between high and normal P4 heifers (15 and 25). Of the genes that were differentially regulated by P4, the majority were unique to a specific day of the estrous cycle/early pregnancy. In conclusion, gene expression in endometria did not differ between pregnant and cycling heifers until Day 16 of pregnancy (i.e. the time of maternal recognition of pregnancy and production of interferon tau by conceptus trophectoderm); however, elevating P4 in early pregnancy programmed changes in gene expression in endometria that are hypothesized to impact early conceptus growth and development. Thus, on Days 5, 7 and 13 differential gene expression was affected by P4, but on Day 16 the conceptus primarily influenced gene expression in uterine endometria of heifers. Endometiral samples were taken from estrous synchronized beef heifers that were either cyclic or confirmed pregnant with either normal or high concentrations of progesterone on Day 5, 7, 13 and 16 of the estrous cycle/early pregnancy.

Project description:An increase in circulating progesterone (P4) concentrations is associated with increased pregnancy success in beef and dairy cattle. Our objective was to ascertain differential effects of elevated P4 concentrations following conception on endometrial gene expression in beef heifers on Days 5, 7, 13 and 16 of pregnancy, corresponding to the morula, blastocyst, elongation and maternal recognition of pregnancy stages, respectively. Estrus was synchronized in beef heifers (N=263). Two-thirds (N=140) were inseminated (Day 0), and all animals were randomly assigned to one of the following treatments: (i) pregnant, high P4; (ii) pregnant, normal P4; (iii) cycling, high P4; (iv) and cycling, normal P4. All high P4 groups received a P4 release intravaginal device (PRID) on Day 3 post-estrus/mating. Tissue was collected on Days 5, 7, 13 or 16 of the cycle or pregnancy, and pregnancy was confirmed by the presence of an appropriately developed embryo/conceptus. PRID insertion elevated (P<0.05) P4 concentrations from Day 3.5 to 8 compared with untreated animals and conceptus size was larger (P<0.05) in animals with elevated P4 on Days 13 and 16 compared with normal P4. Total RNA was extracted from predominantly intercaruncular endometria from the ipsilateral uterine horn. Samples from individual heifers were selected on the basis of their P4 profiles and gene expression was analyzed using bovine Affymetrix microarrays (N=5 per treatment per time point). Microarray data from analyses using Bioconductor GCRMA and Limma packages were subjected to a modified t-test and P-values were adjusted for multiple testing using the Benjamin and Hochberg false discovery rate method. Differentially expressed genes were selected on the basis of an adjusted P-value of <0.01. There were no detectable differences in gene expression in endometria from pregnant and cyclic heifers on Days 5, 7 and 13 post-estrus, but, the expression of 764 genes was altered due to the presence of the conceptus at maternal recognition of pregnancy (Day 16). On Days 5 and 7, elevated P4 in pregnant heifers, altered the expression of 36 and 124 genes respectively but on Days 13 and 16 there were relatively few DEG between high and normal P4 heifers (15 and 25). Of the genes that were differentially regulated by P4, the majority were unique to a specific day of the estrous cycle/early pregnancy. In conclusion, gene expression in endometria did not differ between pregnant and cycling heifers until Day 16 of pregnancy (i.e. the time of maternal recognition of pregnancy and production of interferon tau by conceptus trophectoderm); however, elevating P4 in early pregnancy programmed changes in gene expression in endometria that are hypothesized to impact early conceptus growth and development. Thus, on Days 5, 7 and 13 differential gene expression was affected by P4, but on Day 16 the conceptus primarily influenced gene expression in uterine endometria of heifers.

Project description:The aims of this study were to 1) identify the earliest transcriptional response of the bovine endometrium to the presence of the conceptus (using RNAseq), 2) investigate if these genes are regulated by interferon tau (IFNT) in vivo, and 3) determine if they are predictive of the pregnancy status of postpartum dairy cows. RNAseq identified 459 differentially expressed genes (DEGs) between pregnant and cyclic endometria on day 16. Quantitative real-time PCR analysis of selected genes revealed PARP12, ZNFX1, HERC6, IFI16, RNF213, and DDX58 expression increased in pregnant compared with cyclic endo- metria on day 16 and were directly upregulated by intrauterine infusion of IFNT in vivo for 2 h (P < 0.05). On day 13 following estrous endometrial expression of nine genes increased [ARHGAP1, MGC127874, LIMS2, TBC1D1, FBXL7, C25H16orf71, LOC507810, ZSWIM4, and one novel gene (ENSBTAT00000050193)] and seven genes decreased (SERBP1, SRGAP2, AL7A1, TBK1, F2RL2, MGC128929, and WBSCR17; P < 0.05) in pregnant compared with cyclic heifers. Of these DEGs, significant differences in expression between pregnant and cyclic endometria were maintained on day 16 for F2RL2, LIMS2, LOC507810, MGC127874, TBC1D1, WBSCR17, and ZSWIM4 (P < 0.05) both their expression was not directly regulated by IFNT in vivo. Analysis of the expression of selected interferon-stimulated genes in blood samples from postpartum dairy cows revealed a significant increase (P < 0.05) in expression of ZXFX1, PARP12, SAMD9, and HERC6 on day 18 following artificial insemination in cows subsequently confirmed pregnant compared with cyclic controls. In conclusion, RNAseq identified a number of novel pregnancy-associated genes in the endometrium of cattle during early pregnancy that are not regulated by IFNT in vivo. In addition, a number of genes that are directly regulated by short term exposure to IFNT in vivo are differentially expressed on day 18 following estrus detection in the blood of postpartum dairy cows depending on their pregnancy status. mRNA profiles of pregnant vs not pregnant cross-bred beef heifers at days 13 and 16 (n=5 per group)

Project description:Background: Infertility is a longstanding limitation in livestock production with important economic impact for the cattle industry. Female reproductive traits are polygenic and lowly heritable in nature, thus selection for fertility is challenging. Beef cattle operations leverage estrous synchronization in combination with artificial insemination (AI) to breed heifers and benefit from an early and uniform calving season. A couple of weeks following AI, heifers are exposed to bulls for an opportunity to become pregnant by natural breeding (NB), but they may also not become pregnant during this time period. Focusing on beef heifers, in their first breeding season, we hypothesized that: a- at the time of AI, the transcriptome of peripheral white blood cells (PWBC) differs between heifers that become pregnant to AI and heifers that become pregnant late in the breeding season by NB or do not become pregnant during the breeding season; and b- the ratio of transcript abundance between genes in PWBC classifies heifers according to pregnancy by AI, NB, or failure to become pregnant. Results: We generated RNA-sequencing data from 23 heifers from two locations (A: six AI-pregnant and five NB-pregnant; and B: six AI-pregnant and six non-pregnant). After filtering out lowly expressed genes, we quantified transcript abundance for 12,538 genes. The comparison of gene expression levels between AI-pregnant and NB-pregnant heifers yielded 18 differentially expressed genes (DEGs) (ADAM20, ALDH5A1, ANG, BOLA-DQB, DMBT1, FCER1A, GSTM3, KIR3DL1, LOC107131247, LOC618633, LYZ, MNS1, P2RY12, PPP1R1B, SIGLEC14, TPPP, TTLL1, UGT8, eFDR≤0.02). The comparison of gene expression levels between AI-pregnant and non-pregnant heifers yielded six DEGs (ALAS2, CNKSR3, LOC522763, SAXO2, TAC3, TFF2, eFDR≤0.05). We calculated the ratio of expression levels between all gene pairs and assessed their potential to classify samples according to experimental groups. Considering all samples, relative expression from two gene pairs correctly classified 10 out of 12 AI-pregnant heifers (P=0.0028) separately from the other 11 heifers (NB-pregnant, or non-pregnant). Conclusion: The transcriptome profile in PWBC, at the time of AI, is associated with the fertility potential of beef heifers. Transcript levels of specific genes may be further explored as potential classifiers, and thus selection tools, of heifer fertility.

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Early pregnancy biomarkers

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