Characterisation of endometrial gene expression and metabolic parameters in beef heifers yielding viable or non-viable embryos on Day 7 after insemination

Abstract

Abridged title: Endometrial gene expression and metabolic parameters in subfertile beef heifers. AbstractThe objective of this study was to compare the hormonal, metabolic characteristics and endometrial gene expression profiles in beef heifers yielding either a viable or a degenerate embryo on Day 7 after insemination as a means to explain differences in embryo survival.Oestrus was synchronised in cross bred beef heifers (n=145) using a CIDR-prostaglandin protocol and heifers (n=102) detected in standing oestrus (within 24-48 h post CIDR removal) were inseminated 12-18 h after detection of oestrus (Day 0) with frozen-thawed semen from a single ejaculate of a bull with proven fertility. Blood samples were collected from Day 4 to Day 7 post oestrus to measure progesterone (on Days 4, 5 and 7), insulin and IGF-I (on Days 4 and 6) and urea concentrations (on Day 7). All animals were slaughtered on Day 7. Uterine pH was also determined. Animals from which an embryo was recovered were classified as either having a viable embryo (morula/blastocyst stage); n=32, or a retarded embryo (arrested at 2-to 16-cell stage); n=19. The overall recovery rate was 64%. There was no significant difference in blood parameters measured or uterine pH at slaughter between the heifers with either a viable or retarded embryo. The relative abundance of 9 transcripts out of 53 tested from the endometrial tissue was different between heifers with a viable embryo or retarded embryo: MOGAT1, PFKB2, LYZ2, SVS8, UHRF1, PTGES, AGPAT4, DGKA and HGPD. Both LYZ2 and UHRF1 are associated with regulation of the immune system. PFKFB2 is a mediator in glycolysis and MOGAT, AGPAT4 and DGKA belong to the triglyceride synthesis pathway. PTGES and HGPD belong to the prostaglandin pathway.Both of these metabolic pathways are important for early embryonic development. In conclusion, retarded embryo development in this study was not related to serum progesterone, IGF-I, insulin or urea concentrations nor to uterine pH at slaughter. However, altered expression of genes involved in the prostaglandin and triglyceride pathways, as well as 2 genes that are closely associated with the regulation of immunity in the endometrium may indicate a uterine component to the retardation of the embryos in these beef heifers.

Lysophospholipid acyltransferases

“…The limited role of AGPAT4 was observed in endometrial tissues obtained from beef heifers showing its role in embryo survival. The rate of embryo survival correlated well with the abundant expression of AGPAT4 [25].…”

Discovery of single nucleotide polymorphisms in candidate genes associated with fertility and production traits in Holstein cattle

“…[37]), endometrium related to embryo survival ( DGKA, BSP3, etc. [26]), endometrium in lactating cows compared to non-lactating cows ( APBB1, ST13, etc. [38]) or pregnant cows compared to non-pregnant cows ( ASL, GPLD1, etc.…”

“…Recent studies have revealed genes whose expression in tissues or cells of importance to reproduction vary with reproductive status; these genes are candidates for containing SNPs that impact fertility. For example, genes were identified that were differentially regulated in the brain of cows displaying strong estrus compared to those displaying weak estrus [25], in the endometrium of heifers which produced viable embryos compared to those which produced non-viable embryos [26], and in biopsies from embryos that resulted in live calves as compared to embryos that died following embryo transfer [27]. Genetic variants in the genes differentially expressed in the aforementioned studies and others may be responsible for differences in fertility among animals.…”

Altered endometrial immune gene expression in beef heifers with retarded embryos

“…In order to characterise possible mechanisms leading to the up-or down-74 regulation of the initially identified genes, a further 8 genes were chosen in order to further 75 identify these. 76 Beltman et al (2010). 78…”

“…In a previous study (Beltman et al, 2010) The experimental design used for this study was as previously described (Beltman et al, 58 2010). Oestrus was synchronised in cross-bred beef heifers (n=157) using a Controlled 59…”