Function: Glycosyltransferase that initiates the elongation of O-linked fucose residues attached to EGF-like repeats in the extracellular domain of Notch molecules. Decreases the binding of JAGGED1 to NOTCH2 but not that of DELTA1. Essential mediator of somite segmentation and patterning. Disease: Defects in LFNG are the cause of spondylocostal dysostosis type 3 (SCDO3) [MIM:609813]. An autosomal recessive condition of variable severity associated with vertebral and rib segmentation defects. The main skeletal malformations include fusion of vertebrae, hemivertebrae, fusion of certain ribs, and other rib malformations. Deformity of the chest and spine (severe scoliosis, kyphoscoliosis and lordosis) is a natural consequence of the malformation and leads to a dwarf-like appearance. As the thorax is small, infants frequently have respiratory insufficiency and repeated respiratory infections resulting in life-threatening complications in the first year of life. Similarity: Belongs to the glycosyltransferase 31 family. PTM: A soluble form may be derived from the membrane form by proteolytic processing.