Kindred of IgLON (Kilon; also neuronal growth regulator 1 (NEGR1) and neurotractin) is a 46 kDa member of the IgLON family of molecules. This cell adhesion family includes the proteins LAMP, OBCAM, neurotrimin, CEPU-1, AvGP50, and GP55. Human Kilon shares 97% aa sequence identity with mouse and rat Kilon.
Expression of Kilon is restricted to the brain, specifically in the cerebrum, brain stem, and hippocampus, with much less expression in the cerebellum. In the rat, it was shown that Kilon is already expressed in E16 stage, and its level gradually increases during development. In the cerebral cortex, numerous puncta of Kilon immunoreactivity were visible in all regions, and most were densely distributed in large neurons of layer V. These Kilon positive neurons were identified as pyramidal neurons because of their soma location in layer V, large soma size, and extension of their apical dendrite to layer I. Kilon may be involved in cell-adhesion and may function as a trans-neural growth-promoting factor in regenerative axon sprouting in the mammalian brain.