O-linked N-acetylglucosamine transferase (OGT) is an enzyme involved in the post-translational modification of proteins, performing O-GlcNAcylation by transferring N-acetylglucosamine (GlcNAc) to serine or threonine residues of proteins. OGT is primarily located in the cell nucleus and cytoplasm and is widely expressed in various tissues, particularly at higher levels in the heart, muscles, and brain. OGT participates in various biological processes and signaling pathways, such as gene expression regulation, cell cycle control, stress response, and metabolic regulation. The specific expression and mutations of the OGT gene are associated with various diseases, including cancer, diabetes, and neurodegenerative disorders.