Glycosyltransferase that initiates the elongation of O-linked fucose residues attached to EGF-like repeats in the extracellular domain of Notch molecules (By similarity). Plays an important role in limb outgrowth, it directs the formation and positioning of the apical ectodermal ridge (AER), one of the key organizer centers of vertebrate limb development (PubMed:9121551, PubMed:9121552). 3-O-(alpha-L-fucosyl)-L-threonyl-[EGF-like domain protein] + UDP-N-acetyl-alpha-D-glucosamine = 3-O-(N-acetyl-beta-D-glucosaminyl-(1->3)-alpha-L-fucosyl)-L-threonyl-[EGF-like domain protein] + H(+) + UDP 3-O-(alpha-L-fucosyl)-L-seryl-[EGF-like domain protein] + UDP-N-acetyl-alpha-D-glucosamine = 3-O-(N-acetyl-beta-D-glucosaminyl-(1->3)-alpha-L-fucosyl)-L-seryl-[EGF-like domain protein] + H(+) + UDP Detected at stage 15 in the presumptive dorsal-limb ectoderm. At stages 16-18 expression is restricted to the dorsal side with higher concentration at the dorsoventral boundary and later in the AER. Expression remains restricted to the dorsal ectoderm and the AER until stages 22-24 when it starts to fade in the dorsal ectoderm, but remains in the AER until the last stage examined (27). Belongs to the glycosyltransferase 31 family.