Expression of Vema in the developing mouse spinal cord and optic chiasm

Abstract

A critical phase of nervous system development is the formation of connections between axons and their synaptic targets. Intermediate targets play important roles in axon pathfinding by supplying growing axons with long‐ and short‐ range guidance cues at decision points along their trajectory. We recently identified Vema as a novel membrane‐associated protein that is expressed at the ventral midline of the developing vertebrate central nervous system (CNS). We report that Vema is expressed in the floor plate, an intermediate target for pathfinding commissural axons located at the ventral midline of the developing mouse spinal cord. Interestingly, Vema expression overlaps with the position of an unique population of neurons situated at the midline of the ventral diencephalon and that function as intermediate targets for pathfinding retinal ganglion cell axons. The distribution of Vema in the developing spinal cord and optic chiasm resembles the expression patterns of a variety of molecules known to play important roles in axon guidance, including Robo2, Neuropilin2, and SSEA. The expression of Vema at two key choice points for pathfinding axons suggests an important role for this protein in regulating axon guidance at the midline of the developing mouse central nervous system. J. Comp. Neurol. 451:289–299, 2002. © 2002 Wiley‐Liss, Inc.