We report that the morphogen Hedgehog (Hh) is an axonal chemoattractant in the midline of Drosophila melanogaster embryos. Hh is present in the ventral nerve cord during axonal guidance and overexpression of hh in the midline causes ectopic midline crossing of FasII-positive axonal tracts. In addition, we show that Hh influences axonal guidance via a non-canonical signalling pathway dependent o...

The mouse optic chiasm is a model for axon guidance at the midline and for analyzing how binocular vision is patterned. Recent work has identified several molecular players that influence the binary decision that retinal ganglion cells make at the optic chiasm, to either cross or avoid the midline. An ephrin-B localized to the midline, together with an EphB receptor and a zinc-finger transcript...

Ventral midline cells at different rostrocaudal levels of the central nervous system exhibit distinct properties but share the ability to pattern the dorsoventral axis of the neural tube. We show here that ventral midline cells acquire distinct identities in response to the different signaling activities of underlying mesoderm. Signals from prechordal mesoderm control the differentiation of ros...

Three major axon pathways cross the midline of the vertebrate forebrain early in embryonic development: the postoptic commissure (POC), the anterior commissure (AC) and the optic nerve. We show that a small population of Gfap+ astroglia spans the midline of the zebrafish forebrain in the position of, and prior to, commissural and retinal axon crossing. These glial ;bridges' form in regions devo...