Parental Effects on Epigenetic Programming in Gametes and Embryos of Dairy Cows

Abstract

The bovine represents an important agriculture species and dairy breeds have experienced intense genetic selection over the last decades. The selection of breeders focused initially on milk production, but now includes feed efficiency, health, and fertility, although these traits show lower heritability. The non-genetic paternal and maternal effects on the next generation represent a new research topic that is part of epigenetics. The evidence for embryo programming from both parents is increasing. Both oocytes and spermatozoa carry methylation marks, histones modifications, small RNAs, and chromatin state variations. These epigenetic modifications may remain active in the early zygote and influence the embryonic period and beyond. In this paper, we review parental non-genetic effects retained in gametes on early embryo development of dairy cows, with emphasis on parental age (around puberty), the metabolism of the mother at the time of conception and in vitro culture (IVC) conditions. In our recent findings, transcriptomic signatures and DNA methylation patterns of blastocysts and gametes originating from various parental and IVC conditions revealed surprisingly similar results. Embryos from all these experiments displayed a metabolic signature that could be described as an “economy” mode where protein synthesis is reduced, mitochondria are considered less functional. In the absence of any significant phenotype, these results indicated a possible similar adaptation of the embryo to younger parental age, post-partum metabolic status and IVC conditions mediated by epigenetic factors.

The epigenome of male germ cells and the programming of phenotypes in cattle

“…Another example is provided by the epigenetic alterations that have been observed in semen collected at a peripubertal age. Embryos produced using such peripubertal semen display subtle modifications to the DNA methylome and transcriptome that particularly affect the genes involved in metabolic functions and protein synthesis ( Wu and Sirard, 2020 ). It is noteworthy that only morphologically normal embryos, which would likely have implanted and given birth to progeny, were considered during this study.…”

“…The selection of AI bulls relies on their genetic merit, and they are usually obtained from the breeding of high breeding value sires and high-producing dairy cows. These cows are more likely to experience a negative energy balance in the event of concurrent lactation and gestation, which may lead to an unfavorable in utero environment for the developing fetus ( Wu and Sirard, 2020 ). Otherwise, practices to reduce the generation interval and accelerate genetic gain, such as hormonal treatments of the mothers, embryo technologies, or the hastened growth and puberty of male calves, may have a long-term impact on the sperm epigenome ( Rivera, 2019 ).…”

Epigenetic inheritance of acquired traits through DNA methylation

“…Environmental factors may induce inheritable phenotypes in a nongenetic way in dairy cattle ( Wu & Sirard, 2020 ). A study published by our team showed that specific DNA methylation changes in sperm DNA were associated with bull age (early-, peri- and post-puberty) ( Lambert et al, 2018 ).…”

“…A study published by our team showed that specific DNA methylation changes in sperm DNA were associated with bull age (early-, peri- and post-puberty) ( Lambert et al, 2018 ). A subsequent study showed that the age of the bull correlated with DNA methylation and transcriptome alterations in blastocysts, indicating a potential effect of age on offspring development ( Wu et al, 2020 ). Additionally, metabolic stress in cows resulted in alterations of the DNA methylation profile of embryos.…”

EMBRYO SURVIVAL TO ACCELERATE GENETIC PROGRESS IN DAIRY HERDS (review)

“…Э п и г е н е т и ч е с к и й а с п е к т в ы ж и в а е м о с т и э м б р и о н а. В живых организмах широко распространена эпигенетическая регуляция активности генов, которая не связана с изменением первичной структуры ДНК, но модифицирует работу генома в зависимости от внутренних и внешних факторов (110). Показано, что эпигенетическая регуляция осуществляется через химическую модификацию структуры ДНК (метилирование ДНК, модификации гистонов, некодирующие RNAs) или хроматина (111). Метилирование ДНК в бластоцистах -обратимый и динамический эпигенетический механизм, участвующий в ремоделировании структуры хроматина, в том числе в критических регуляторных областях генома, и тем самым влияющий на экспрессию генов (112).…”