NAD ⁺ Metabolism Licenses Zygotic Genome Activation via PARP7‐Mediated ADP‐Ribosylation of UHRF1 in Mouse Early Embryos

ABSTRACT Zygotic genome activation (ZGA) is a critical developmental milestone whose metabolic regulation remains unclear. This study identifies a pivotal role for Nicotinamide adenine dinucleotide (NAD ⁺ ) metabolism in regulating ZGA through poly(ADP‑ribose) polymerase 7(PARP7)‐mediated ADP‐ribosylation. Using ultra‐low input embryo metabolomics, we profiled metabolism from zygote to blastocyst, revealing a significant NAD ⁺ decline at the 2‐cell stage. This shift coincided with specific upregulation of the mono‐ADP‐ribosyltransferase PARP7, confirmed by transcriptomics, quantitative RT‐PCR, western blot, and immunofluorescence. Genetic knockdown via trim‐away technology or pharmacological inhibition with RBN‐2397 caused developmental delay/arrest at the 2‐cell stage, impaired blastocyst formation, and defective ZGA. Mechanistically, PARP7 deficiency reduced chromatin accessibility (ATAC‐seq), diminished H3K4ac and H3K27ac marks, and impaired RNA polymerase II transcription. Integrated proteomics and ADP‐ribosylome analysis of late 2‐cell embryos identified UHRF1 as a key PARP7 target, mono‐ADP‐ribosylated at lysines K30 and K31. This modification stabilized UHRF1 protein (cycloheximide chase), and UHRF1 overexpression partially rescued the transcriptional defects associated with ZGA from PARP7 inhibition. Our findings establish a metabolic‐epigenetic axis wherein NAD ⁺ metabolism, via PARP7‐mediated ADP‐ribosylation of UHRF1, regulates chromatin remodeling and transcriptional activation during ZGA, offering fundamental insights into early development.