Olfactomedin-2 mediates development of the anterior central nervous system and head structures in zebrafish

Olfactomedins comprise a diverse family of secreted glycoproteins, which includes noelin, tiarin, pancortin and gliomedin, implicated in development of the nervous system, and the glaucoma-associated protein myocilin. Here we show in zebrafish that olfactomedin-2 (OM2) is a developmentally regulated gene, and that knockdown of protein expression by morpholino antisense oligonucleotides leads to perturbations of nervous system development. Interference with OM2 expression results in impaired development of branchiomotor neurons, specific disruption of the late phase branchiomotor axon guidance, and affects development of the caudal pharyngeal arches, olfactory pits, eyes and optic tectum. Effects of OM2 knockdown on eye development are likely associated with Pax6 signaling in developing eyes, as Pax6.1 and Pax6.2 mRNA expression patterns are altered in the eyes of OM2 morphants. The specific absence of most cartilaginous structures in the pharyngeal arches indicates that the observed craniofacial phenotypes may be due to perturbed differentiation of cranial neural crest cells. Our studies show that this member of the olfactomedin protein family is an important regulator of development of the anterior nervous system.