Glycosyltransferase that initiates the elongation of O-linked fucose residues attached to EGF-like repeats in the extracellular domain of Notch molecules (By similarity). Regulates neurogenesis in the hindbrain; involved in boundary cell specification via Notch-mediated activation of wnt1 expression (PubMed:15068793, PubMed:15659486). 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 Expressed both maternally and zygotically. At the tailbud stage, expressed weakly in the adaxial cells and the future brain. From the 3-somite stage, strong expression in the adaxial cells and weak expression in the somites and tailbud. During somitogenesis, expression in the brain is gradually restricted to and up-regulated in the tectum and rhombomere boundary cells. Belongs to the glycosyltransferase 31 family.