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[P247]: Modulation of growth cone repellent responses
Author(s) -
Sanford S.,
Pfenninger K.
Publication year - 2006
Publication title -
international journal of developmental neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.761
H-Index - 88
eISSN - 1873-474X
pISSN - 0736-5748
DOI - 10.1016/j.ijdevneu.2006.09.305
Subject(s) - library science , citation , center (category theory) , health science , research center , sociology , psychology , political science , computer science , medicine , medical education , law , chemistry , crystallography
migration, RGC axons need to cross the midline, travel dorsalwards through the diencephalon, and recognize the midbrain target, the optic tectum. The growing axons find their way by interpreting guidance cues presented to the growth cones. Using the optic pathway of zebrafish, we are investigating the role of semaphorins (Semas) in patterning. Semaphorins make up a large family of mainly repulsive guidance cues that signal through plexin receptors. Class three Semas (Sema3s) are secreted and play a role in patterning the developing nervous system. Sema3s are unique in that they require neuropilin as a coreceptor with plexin. It has recently been shown that neuropilin mRNA is expressed in zebrafish RGCs at a time when their axons are extending (Liu et al., 2004). The presence of Sema3-selective receptors in RGCs suggests that Sema3s may be actively directing the development of the optic pathway. As a first step to identifying Sema3s important in RGC axon guidance we performed in situ hybridization with digoxygenin-labeled antisense mRNA probes for several sema3 genes (sema3aa, sema3fa, sema3fb, sema3ga, sema3gb) over the time when zebrafish RGCs first leave the eye (34 h post fertilization (hpf)), and reach and fully innervate the optic tectum (48–60 hpf). In the differentiating retina, sema3fa is expressed at early stages (30 hpf) in the RGC layer. Sema3aa is expressed in the telencephalon, apparently just anterior to the route RGC axons take through the diencephalon. Several sema3s were expressed either in broad (sema3aa, sema3ga, sema3fa) or highly restricted expression (sema3fb, sema3gb) patterns in the optic tectum at the time of RGC axon entry. These data suggest that several different sema3s are expressed in or near the optic pathway and could guide RGC axons. We are currently testing this idea by loss-offunction approaches.