May function as a homophilic adhesion molecule. Expressed in the dorsal region of the neural keel as somatogenesis proceeds before 25 hpf. At 25 hpf, expression is highest in the neural plate, in the brain including telencephalon, diencephalon, tectum and the rhombomere boundary. Highly expressed in lens, germinal ganglion, otic capsule and rhombomeres 2-7. Weakly expressed in trunk and tail. Expression is particularly high in otic capsule at 48 hpf. Belongs to the CD99 family.