NRP1-mediated Sema3A signals coordinate laminar formation in the developing chick optic tectum

• Published in: Development (Cambridge) Vol. 141; no. 18; pp. 3572 - 3582
• Main Authors: Watanabe, Yuji, Sakuma, Chie, Yaginuma, Hiroyuki
• Format: Journal Article
• Language: English
• Published: England 01.09.2014
• Subjects: Animals; Bromodeoxyuridine; Cell Movement - physiology; Chick Embryo; Electroporation; Fluorescence; In Situ Hybridization; Microscopy, Confocal; Microtubule-Associated Proteins - metabolism; Neuropilin-1 - metabolism; Organogenesis - physiology; Semaphorin-3A - metabolism; Signal Transduction - physiology; Superior Colliculi - embryology; Superior Colliculi - metabolism; Sema3A; NRP1; Optic tectum; Laminar formation; Chick; Cell migration
• ISSN: 0950-1991; 1477-9129
• DOI: 10.1242/dev.110205

The optic tectum comprises multiple layers, which are formed by radial and tangential migration during development. Here, we report that Neuropilin 1 (NRP1)-mediated Sema3A signals are involved in the process of tectal laminar formation, which is elaborated by tangential migration. In the developing chick tectum, NRP1, a receptor for Sema3A, is expressed in microtubule-associated protein 2 (MAP2)-positive intermediate layers IV and V. Sema3A itself is a diffusible guidance factor and is expressed in the overlying layer VI. Using stable fluorescent labeling of tectal cells, we show that MAP2-positive intermediate layers are formed by the neurons that have been dispersed by tangential migration along the tectal efferent axons. When Sema3A was mis-expressed during laminar formation, local Sema3A repelled the tangential migrants, thus eliminating MAP2-positive neurons that expressed NRP1. Furthermore, in the absence of the MAP2-positive neurons, tectal layers were disorganized into an undulated form, indicating that MAP2-positive intermediate layers are required for proper laminar formation. These results suggest that NRP1-mediated Sema3A signals provide repulsive signals for MAP2-positive neurons to segregate tectal layers, which is important in order to coordinate laminar organization of the optic tectum.