Expression of multiple class three semaphorins in the retina and along the path of zebrafish retinal axons

Abstract

Retinal ganglion cells (RGCs) extend axons that exit the eye, cross the midline at the optic chiasm, and synapse on target cells in the optic tectum. Class three semaphorins (Sema3s) are a family of molecules known to direct axon growth. We undertook an expression screen to identify sema3s expressed in the retina and/or brain close to in-growing RGC axons, which might therefore influence retinal-tectal pathfinding. We find that sema3Aa, 3Fa, 3Ga, and 3Gb are expressed in the retina, although only sema3Fa is present during the time window when the axons extend. Also, we show that sema3Aa and sema3E are present near or at the optic chiasm. Furthermore, sema3C, 3Fa, 3Ga, and 3Gb are expressed in regions of the diencephalon near the path taken by RGC axons. Finally, the optic tectum expresses sema3Aa, 3Fa, 3Fb, and 3Gb. Thus, sema3s are spatiotemporally placed to influence RGC axon growth. Developmental Dynamics 236:2918 -2924, 2007.

Ipsilateral and Contralateral Retinal Ganglion Cells Express Distinct Genes during Decussation at the Optic Chiasm

“…Tbx20 functions in heart development (Plageman and Yutzey, 2005) and cranial motor neuron migration (Song et al, 2006). The expression and guidance roles of semaphorin family members have been demonstrated at multiple points along the path of retinal axons (Callander et al, 2007; Kuwajima et al, 2012). Sema3e is known to be expressed at the optic chiasm (Sakai and Halloran, 2006), where it influences midline crossing decisions in the fish optic chiasm.…”

“…Here, we show that it is also expressed in a subset of contralateral RGCs, raising the question of why this repulsive guidance cue is also expressed by RGCs. One possible explanation is the demonstration that RGC-secreted Sema3e regulates retinal angiogenesis through interactions with Plexin-D1 expressed on endothelial cells of sprouting blood vessels (Callander et al, 2007). However, whether Sema3e has a further function in regulating contralateral RGC axon growth and guidance has not been explored.…”

Expression of pro‐ and anti‐angiogenic factors during the formation of the periocular vasculature and development of the avian cornea

“…Semaphorins are a group of secreted and membrane-associated proteins that play important roles during embryonic development and adulthood. All vertebrate semaphorins (semaphorins 3-7) signal by directly binding plexins (plexinA-D) or through tyrosine kinase receptors Npn1 and Npn2 with plexin co-receptors (Callander et al, 2007;Bagri et al, 2009). In this group, the secreted Sema3A, Sema3E, and Sema3G have been associated with vascular development and patterning (Bates et al, 2003;Serini et al, 2003;Gitler et al, 2004;Gu, 2005;Kutschera et al, 2011).…”

Neuropilin-1 biases dendrite polarization in the retina

“…It is at this point that Xenopus RGCs initiate expression of Nrp1 and Plxna1, equipping their axons with the ability to respond to Sema3a as a repellent both in vitro and in vivo (AtkinsonLeadbeater et al, 2010;Campbell et al, 2001). Intriguingly, a number of Sema3 genes are expressed in the retina after the majority of RGC axons have left the eye and the dendrites start to emerge (Callander et al, 2007;Koestner et al, 2008). As such, we investigated whether Nrp and PlxnA receptors regulate the growth of RGC dendrites in vivo.…”