Perturbing nuclear glycosylation in the mouse preimplantation embryo slows down embryonic growth

The only known form of intracellular protein glycosylation (O-GlcNAc) is reversible and has been mapped on thousands of cytoplasmic and nuclear proteins, including RNA polymerase II, transcription factors and chromatin modifiers. The O-GlcNAc modification is catalyzed by a single enzyme known as O-GlcNAc Transferase (OGT), that is required for mammalian early development. Remarkably, the regulatory function of protein O-GlcNAcylation in the embryo as well as the embryonic O-GlcNAc proteome remain unknown. Here, we devised a new method to enzymatically remove O-GlcNAc from preimplantation embryonic nuclei, where it accumulates coincidently with embryonic genome activation (EGA). Unexpectedly, the depletion of nuclear O-GlcNAc to undetectable levels has no impact on EGA, but dampens the transcriptional activation of the translational machinery, and triggers a spindle checkpoint response. These molecular alterations were phenotypically associated with a developmental delay starting from early cleavage stages and persisting after embryo implantation, establishing a novel link between nuclear glycosylation and embryonic growth.