* During O-Fuc modification of TSR1 (thrombospondin type 1) repeat, the first step involves the transfer of fuc by Pofut2 to Ser/Thr in this domain. The absence of Pofut2 in mice results in early embryonic lethality with defects in gastrulation. 
* The next step involves the transfers glucose to O-Fuc by a gene encoding the β3-glucosyltransferase, B3GLCT or B3GALTL. Mutations in B3GLCT in humans results in a multifaceted severe developmental disorder known as Peters-plus syndrome.
* Besides O-fuc, and C-mannosylation also occur on TSR1/thrombospondin-1 domains.