Unité Génétique Biologie du Développement, Institut Curie, UMR3215/INSERM U394, Paris, France.
Curr Top Dev Biol. 2013;104:293-328. doi: 10.1016/B978-0-12-416027-9.00009-7.
The early mammalian embryo is marked by genome-wide parental epigenetic asymmetries, which are directly inherited from the sperm and the oocyte, but are also amplified a few hours after fertilization. The yin-yang of these complementary parental programs is essential for proper development, as uniparental embryos are not viable. The majority of these parental asymmetries are erased, as the embryonic genome assumes its own chromatin signature toward pluripotency and then differentiation, reducing the risk for haploinsufficiency. At a few loci, however, parent-of-origin information persists through development, via maintenance and protective complexes. In this review, we discuss the parental asymmetries that are inherited from the gametes, the forces involved in their elimination, reinforcement or protection, and how this influences the embryonic program. We highlight the gradual loss of all parental asymmetries occurring throughout development, except at imprinted loci, which maintain distinct parent-of-origin chromatin and transcriptional characteristics for life. A deeper understanding of the nongenetic contributions of each germline is important to provide insight into the origin of non-Mendelian inheritance of phenotypic traits, as well as the risk of incompatibilities between parental genomes.
早期哺乳动物胚胎具有全基因组的亲代表观遗传不对称性，这些不对称性直接来自精子和卵子，但在受精后几个小时也会被放大。这些互补的亲代程序的阴阳平衡对于正常发育至关重要，因为单倍体胚胎是不可存活的。这些亲代不对称性中的大多数都会被抹去，因为胚胎基因组朝着多能性和分化形成自己的染色质特征，从而降低了单倍体不足的风险。然而，在少数几个位点，通过维持和保护复合物，来自亲本的信息会通过发育持续存在。在这篇综述中，我们讨论了从配子中遗传的亲代不对称性、涉及它们消除、强化或保护的力量，以及这如何影响胚胎程序。我们强调了在整个发育过程中除印记基因座外，所有亲代不对称性逐渐丢失的现象，因为印记基因座会维持独特的亲本来源的染色质和转录特征。深入了解每个生殖系的非遗传贡献对于了解表型特征的非孟德尔遗传的起源以及亲本基因组之间不兼容的风险非常重要。
