This family consists of the N-terminal region of several mammalian and one bird sequence from Gallus gallus (Chicken). All of the mammalian proteins are hypothetical and have no known function but RGMA from chicken is annotated as being a repulsive guidance molecule (RGM). RGM is a GPI-linked axon guidance molecule of the retinotectal system. 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.