Parental Epigenetic Asymmetry in Mammals - Current Topics in Developmental Biology - page 288

CHAPTER NINE

Parental Epigenetic Asymmetry
in Mammals

Rachel Duffié, Déborah Bourc'his 1
Unit´ G´n´tique Biologie du D´veloppement, Institut Curie, UMR3215/INSERMU394, Paris, France
1 Corresponding author: e-mail address: [e-mail]

Contents
1. Introduction 294

1.1 Flexibility of histone-associated information 294

1.2 Long-term potential of DNA methylation-associated information 295

1.3 Forces exerted to reduce parental epigenetic inheritance 296

2. Generating Asymmetric Nuclear-Based Information in Parental Gametes 297

2.1 Sex-specific chromatin organization and histone modifications 298

2.2 Sex-specific DNA methylation patterns 300

3. Immediate Inheritance and Reinforcement of Parental Asymmetry in the One-Cell

Zygote 307

3.1 Reshuffling of histone variants and modifications 309

3.2 Parent-specific DNA methylation fates 310

4. Global Loss and Specific Retention of Parental Asymmetries During
Preimplantation Development

312

4.1 Selective protection of parent-specific DNA methylation patterns 312

4.2 Imprinted X-chromosome inactivation 314

5. Scarce Maintenance of Parental Epigenetic Asymmetry After Embryo Implantation
and Throughout Adulthood

316

5.1 Reduction of germline DMRs 317

5.2 Emergence of somatic DMRs 319

5.3 Parent-specific histone modifications at imprinted loci 319

6. Conclusions 320

Acknowledgments 321

References 321

Abstract
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,