McAdams, Brian2018-11-282018-11-282018-08https://hdl.handle.net/11299/201142University of Minnesota Ph.D. dissertation. August 2018. Major: Neuroscience. Advisor: Steve McLoon. 1 computer file (PDF); ix, 209 pages.Axons of retinal ganglion cells grow from the eye to the visual centers of the brain during development. Evidence suggests that adhesive and anti-adhesive interactions between growing axons and the cells and extracellular matrix in their environment guide retinal axons to their central targets. Proteoglycans are a family of extracellular glycoproteins that could contribute to these interactions. The present study investigated the potential interaction and influence of glycosaminoglycans with retinal axons in situ and in vitro. Immunostaining showed both chondroitin sulfate and keratan sulfate proteoglycans throughout the retinotectal pathway during the period of axon growth. Retinal neurites extending from explants in culture were immunopositive for chondroitin sulfate indicating that retinal axons may contribute proteoglycans to the pathway. Retinal neurite behavior was examined in the presence of soluble glycosaminoglycans. High concentrations of chondroitin sulfate promoted retinal neurite growth on normally less adhesive substrates, which suggests that this glycosaminoglycan may promote neurite outgrowth in some conditions. Retinal axon growth was also examined in nanomelic chicks, mutants which do not secrete a large chondroitin sulfate proteoglycan, aggrecan. Aggrecan immunostaining was colocalized with retinal axons in normal embryos. For the parameters studied, retinal axon growth and guidance appeared unaffected in nanomelic mutants, which suggested that aggrecan was not essential for retinal axon growth or guidance. Its spatiotemporal distribution, however, suggests that aggrecan has other developmental roles in this system. Collectively, the data are ambiguous regarding the role of chondroitin sulfate and keratan sulfate proteoglycans relative to retinal axon growth during development. Proteoglycans are capable of influencing retinal axon growth in vitro, but whether they influence growth in vivo and the nature of this influence will require future investigations.enChondroitnDevelopmentGrowthGuidanceProteoglycanRetinotectalThesis or Dissertation