Developmentally programmed tankyrase activity upregulates ß-catenin and licenses progression of embryonic genome activation

Embryonic genome activation (EGA) is orchestrated by an intrinsic developmental program initiated during oocyte maturation with translation of stored maternal mRNAs. Here we show that tankyrase, a poly(ADP-ribosyl) polymerase that regulates ß-catenin levels, undergoes programmed translation during oocyte maturation and serves an essential role in mouse EGA. Newly translated TNKS triggers proteasomal degradation of axin, reducing targeted destruction of ß-catenin and promoting ß-catenin-mediated transcription of target genes, including Myc. MYC mediates ribosomal RNA transcription in 2-cell embryos, supporting global protein synthesis. Suppression of tankyrase activity using knockdown or chemical inhibition causes loss of nuclear ß-catenin and global reductions in transcription and histone H3 acetylation. Chromatin and transcriptional profiling indicate that development arrests prior to the mid-2-cell stage, mediated in part by reductions in ß-catenin and MYC. These findings indicate that post-transcriptional regulation of tankyrase serves as a ligand-independent developmental mechanism for post-translational ß-catenin activation and is required to complete EGA. Overall design: Examination of open chromatin regions and transcription in 2-cell embryos following inhibition of tankyrase activity relative to controls. Grant ID: 1ZIAES102985 Funding source: The Intramural Research Program of the NIH, National Institutes of Environmental Health Sciences Title: Environmental influence on gametes and embryos Recipient: Carmen J. Williams