Apart from other applications, the hypomorphic sxcH537A mutant is a tool that can be used to investigate the role of dHcf O-GlcNAc, potentially developed as a model to investigate the role of OGT in XLID and investigate O-GlcNAc occupancy in the Ph Ser/Thr-rich stretch. The gene discussed is OGT; the disease is cask-related x-linked intellectual disability.