Class 3 semaphorins in the developing and injured rat visual system

[Truncated abstract] This dissertation details changes in expression of the Class 3 Semaphorins (Sema3s) and their receptors in the developing and injured rat visual system. Due to a lack of verified antibodies against the great majority of Sema3 ligands and their receptor components, changes in gene expression were primarily analysed by quantitative reverse transcriptase polymerase chain reaction (qPCR), and in situ hybridisation of mRNA transcripts. Transcripts analysed were Sema3a, Sema3b, Sema3c, Sema3e, Sema3f, Nrp1, Nrp2, Plxna1, Plxna2, Plxna3, Plxna4, and L1cam. Data from the Allen Brain Atlas, and Gensat atlas were also examined and related to the new developmental qPCR data. To investigate cellular responses to the Sema3s, immunopurified retinal ganglion cells, the only efferent neurons of the retina, were tested in vitro for their response to exogenous recombinant Sema3 ligands in a growth cone collapse assay. During development, it was found that several Sema3 ligands and receptors changed transcript expression in both the retina and superior colliculus. In the retina, Sema3a, Sema3b, Sema3c, Sema3e, Sema3f, Nrp1, Plxna2, Plxna3, and Plxna4 had statistically significant changes in mRNA expression during development. During development of the superior colliculus, all genes of interest, bar L1cam, had statistically significant changes in transcript expression. The nature and timing of these changes suggested a range of possible roles in guidance, apoptosis, and synaptogenesis, in the retina and superior colliculus. After unilateral optic nerve transection, there are delayed and late changes in Sema3 ligand and receptor mRNA expression in both the retina and superior colliculus.