Expression of class-3 semaphorins and their receptors in the neonatal and adult rat retina.
PURPOSE: Semaphorins comprise a family of molecules that influence the growth and guidance of neuronal processes. Class-3 semaphorins are secreted proteins, and their effects are mediated by neuropilin ( NP) and plexin (Plx) receptors. There is considerable information on mechanisms that influence axonal guidance and plasticity in the mammalian visual system, but a role for semaphorins has received less scrutiny. The purpose of the current study was to survey class-3 semaphorin and cognate receptor expression in young and adult rat retinas. METHOD: The mRNA expression of five class-3 semaphorins (3A, 3B, 3C, 3E, and 3F) and receptor subtypes NP-1 and -2 and plexins A1 and A2 was determined, by using riboprobes and in situ hybridization on cryosections of newborn (postnatal day [P]0), juvenile (P14), and adult rat retinas. Retinal ganglion cells (RGCs) were identified by retrograde labeling after injections of a fluorescent tracer (Fluorogold, FG) into the superior colliculus. Hybridized sections were also immunostained to identify specific retinal cell classes. RESULTS: mRNA expression for all five members of the class-3 semaphorin family was seen in adult FG-labeled RGCs. Qualitatively, expression was highest for semaphorins 3B and 3C, and lowest for 3A. Levels of mRNA expression in RGCs were lower in newborn retinas but were adult-like by P14. Expression by different cell types in the inner nuclear layer was also seen, especially at P14. Expression of NP-2 and PlxA2 mRNAs was evident in developing inner nuclear and ganglion cell layers at birth. Expression increased postnatally and was maintained into adulthood. NP-1 and PlxA1 expression was also present, but at comparatively lower levels. CONCLUSIONS: The presence of class-3 semaphorins and their receptors in neonatal and adult rat retina suggests a potential role for these proteins in retinal development and in the maturation, stabilization, and plasticity of mammalian primary visual pathways.[1]References
- Expression of class-3 semaphorins and their receptors in the neonatal and adult rat retina. de Winter, F., Cui, Q., Symons, N., Verhaagen, J., Harvey, A.R. Invest. Ophthalmol. Vis. Sci. (2004) [Pubmed]
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