This family represents the C-terminal region of repulsive guidance molecule (RGM), although in some sequences it represents the full protein. RGM is a GPI-linked axon guidance molecule of the retinotectal system, and controls cell motility, adhesion, immune cell regulation and systemic iron metabolism [2,3]. RGM is repulsive for a subset of axons, those from the temporal half of the retina. Temporal retinal axons invade the anterior optic tectum in a superficial layer, and encounter RGM expressed in a gradient with increasing concentration along the anterior-posterior axis. Temporal axons are able to receive posterior-dependent information by sensing gradients or concentrations of guidance cues. Thus, RGM is likely to provide positional information for temporal axons invading the optic tectum in the stratum opticum [1]. This domain is responsible for neogenin (NEO1) binding [2,3].

1: RGM is a repulsive guidance molecule for retinal axons. Monnier PP, Sierra A, Macchi P, Deitinghoff L, Andersen JS, Mann M, Flad M, Hornberger MR, Stahl B, Bonhoeffer F, Mueller BK; Nature 2002;419:392-395. PMID:12353034

2: Repulsive guidance molecule is a structural bridge between neogenin and bone morphogenetic protein. Healey EG, Bishop B, Elegheert J, Bell CH, Padilla-Parra S, Siebold C; Nat Struct Mol Biol. 2015;22:458-465. PMID:25938661

3: Simultaneous binding of Guidance Cues NET1 and RGM blocks extracellular NEO1 signaling. Robinson RA, Griffiths SC, van de Haar LL, Malinauskas T, van Battum EY, Zelina P, Schwab RA, Karia D, Malinauskaite L, Brignani S, van den Munkhof MH, Dudukcu O, De Ruiter AA, Van den Heuvel DMA, Bishop B, Elegheert J, Aricescu AR, Pasterkamp RJ, Siebold C; Cell. 2021;184:2103-2120. PMID:33740419