Dynamic Change of R-Loop Implicates in the Regulation of Zygotic Genome Activation in Mouse

• Published in: International journal of molecular sciences Vol. 23; no. 22; p. 14345
• Main Authors: Lee, Hyeonji, You, Seong-Yeob, Han, Dong Wook, La, Hyeonwoo, Park, Chanhyeok, Yoo, Seonho, Kang, Kiye, Kang, Min-Hee, Choi, Youngsok, Hong, Kwonho
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 18.11.2022; MDPI
• Subjects: Animals; Antibodies; Antigens; Biosynthesis; Cancer; Cell cycle; Chromatin; Chromatin - genetics; Cisplatin; Deoxyribonucleic acid; DNA; DNA biosynthesis; DNA damage; DNA replication; DNA structure; Doxorubicin; Embryonic Development - genetics; Embryos; Gametocytes; Gene Expression Regulation, Developmental; Gene regulation; Genomes; Homeostasis; In vitro fertilization; Metabolism; Metaphase; Mice; Mitochondrial DNA; Nucleic acids; Oocytes; Pronucleus; R-loop; R-Loop Structures; R-loops; Replication; RNA polymerase; Splicing; Transcription; Zygote; Zygotes; zygotic genome activation; DNA replication; transcription; R-loop; zygotic genome activation
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms232214345

In mice, zygotic genome activation (ZGA) occurs in two steps: minor ZGA at the one-cell stage and major ZGA at the two-cell stage. Regarding the regulation of gene transcription, minor ZGA is known to have unique features, including a transcriptionally permissive state of chromatin and insufficient splicing processes. The molecular characteristics may originate from extremely open chromatin states in the one-cell stage zygotes, yet the precise underlying mechanism has not been well studied. Recently, the R-loop, a triple-stranded nucleic acid structure of the DNA/RNA hybrid, has been implicated in gene transcription and DNA replication. Therefore, in the present study, we examined the changes in R-loop dynamics during mouse zygotic development, and its roles in zygotic transcription or DNA replication. Our analysis revealed that R-loops persist in the genome of metaphase II oocytes and preimplantation embryos from the zygote to the blastocyst stage. In particular, zygotic R-loop levels dynamically change as development proceeds, showing that R-loop levels decrease as pronucleus maturation occurs. Mechanistically, R-loop dynamics are likely linked to ZGA, as inhibition of either DNA replication or transcription at the time of minor ZGA decreases R-loop levels in the pronuclei of zygotes. However, the induction of DNA damage by treatment with anticancer agents, including cisplatin or doxorubicin, does not elicit genome-wide changes in zygotic R-loop levels. Therefore, our study suggests that R-loop formation is mechanistically associated with the regulation of mouse ZGA, especially minor ZGA, by modulating gene transcription and DNA replication.