Meta-Biol

• Pathways

The Fringe family (CAZy family GT31) of glycosyltransferases in mammals includes LFNG (lunatic fringe; MIM:602576), MFNG (manic fringe; MIM:602577) and RFNG (radical fringe; MIM:602578). Fringe enzymes function in the Golgi apparatus where they initiate the elongation of O -inked fucose on fucosylated peptides by the addition of a beta-1,3-N-acetylglucosaminyl group (GlcNAc) (Moloney et al. 2000). Fringe enzymes elongate conserved O fucosyl residues conjugated to EGF repeats of NOTCH, modulating NOTCH activity (Cohen et al. 1997, Johnston et al. 1997) by decreasing the affinity of NOTCH extracellular domain for JAG ligands (Bruckner et al. 2000).

The spondylocostal dysostoses (SCDs) are a group of disorders that arise during embryonic development by a disruption of somitogenesis. The Notch signalling pathway is essential for somitogenesis, the precursors of vertebra and associated musculature. Defects in one of the Fringe enzymes, beta-1,3-N-acetylglucosaminyltransferase lunatic fringe (LFNG), can cause spondylocostal dysostosis, autosomal recessive 3 (SCDO3; MIM:609813), a condition of variable severity associated with vertebral and rib segmentation defects (Sparrow et al. 2006). The missense mutation F188L can result in SCDO3 by not being able to modulate Notch activity (Sparrow et al. 2006).