Location: Reproduction ResearchTitle: Genes associated with chromatin modification within the swine placenta are differentially expressed due to factors associated with season
Submitted to: Frontiers in Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2020
Publication Date: 9/23/2020
Citation: Rempel, L.A., Parrish, J.J., Miles, J.R. 2020. Genes associated with chromatin modification within the swine placenta are differentially expressed due to factors associated with season. Frontiers in Genetics. 11:1019. https://doi.org/10.3389/fgene.2020.01019.
Interpretive Summary: Epigenetics is the result of environmental factors altering the DNA output, without altering the DNA sequence. Environmental factors, such as season, have been shown to impact reproductive performance in swine. ARS scientists along with the University of Wisconsin, evaluated the difference in known epigenetic-associated genes in placenta that were derived from semen collected during warm or cool periods, semen that was stored as cooled-extended or cryopreserved, and breeding females in summer or winter. The season in which the females were bred, summer or winter, elicited the greatest number of genes that were different within the placenta. Three genes were influenced by the interaction of semen collection season, semen storage, and breeding season. Although the swine industry regulates environmental influence of summer by using climate-controlled housing, these data suggest season, or time of the year, can still influence placental development. These subtle changes likely occur to improve survivability of the developing fetuses under different environmental conditions. These data are novel findings and support future studies investigating the influences season has on placental development.
Technical Abstract: Seasonal reproductive inefficiency is still observed in modern swine facilities. We previously reported global placental methylation activity was reduced from summer breedings and tended to be less from semen collected during cooler periods. The objective of the current study was to evaluate chromatin modification marks within swine placenta in relationship to breeding season, semen collection season, and semen storage. White composite gilts were artificially inseminated in August or January using single-sire semen that was collected during warm or cool periods and stored as either cryopreserved or cooled-extended. Gilts were harvested 45 days post-breeding, and placental samples from the smallest, average, and largest fetus in each litter were collected and stored at -80°C until RNA extraction. An RT2 Profiler assay featuring 84 known chromatin modification enzyme targets was performed using placental RNA pooled by litter. Real-time quantitative polymerase chain reaction results were analyzed using the MIXED procedure, and P-values were Hochberg corrected using the MULTTEST procedure in SAS. The complete model included the fixed effects of breeding season (winter or summer), semen collection season (cool or warm), semen storage (cooled-extended or cryopreserved), interactions; boar as repeated effect; and plate as random effect. If interactions were not significant, only the main effects were tested. The genes, ATF2, AURKA, and KDM5B, were different (P < 0.05) by interaction of breeding season, semen collection season, and semen storage. In general, the greatest (P < 0.05) expression was in placentas derived from summer breedings. Expression of AURKA was also influenced by semen collection and storage. Expression of placental KDM5B from winter breedings was also greater (P < 0.05) from semen collected during cool periods. Placental expressions of ASH2L, DNMT3B, ESCO1, HDAC2, ING3, KDM6B, MYSM1, and SMYD3 were greater (P < 0.05) from summer breedings. Increased expressions of known chromatin modification genes, from placentas derived from summer breedings, are likely responsible for differences in gene transcription between summer- or winter-derived placentas.