PT - JOURNAL ARTICLE AU - Toru Matsukawa AU - Kayo Sugitani AU - Kazuhiro Mawatari AU - Yoshiki Koriyama AU - Zhongwu Liu AU - Masayuki Tanaka AU - Satoru Kato TI - Role of Purpurin as a Retinol-Binding Protein in Goldfish Retina during the Early Stage of Optic Nerve Regeneration: Its Priming Action on Neurite Outgrowth AID - 10.1523/JNEUROSCI.1809-04.2004 DP - 2004 Sep 22 TA - The Journal of Neuroscience PG - 8346--8353 VI - 24 IP - 38 4099 - http://www.jneurosci.org/content/24/38/8346.short 4100 - http://www.jneurosci.org/content/24/38/8346.full SO - J. Neurosci.2004 Sep 22; 24 AB - Unlike mammals, the fish optic nerve can regenerate after injury. So far, many growth or trophic factors have been shown as an axon-regenerating molecule. However, it is totally unknown what substance regulates or triggers the activity of these factors on axonal elongation. Therefore, we constructed a goldfish retina cDNA library prepared from the retina treated with optic nerve transection 5 d previously, when it was just before regrowing optic axons after injury. A cDNA clone for goldfish purpurin for which expression was upregulated during the early stage of optic nerve regeneration was isolated from the retina cDNA library. Purpurin was discovered as a secretory retinol-binding protein in developing chicken retinas. Levels of purpurin mRNA and protein transiently increased and rapidly decreased 2–5 d and 10 d after axotomy, respectively. Purpurin mRNA was localized to the photoreceptor cells, whereas the protein was diffusely found in all of the retinal layers. A recombinant purpurin alone did not affect any change of neurite outgrowth in explant culture of the control retina, whereas a concomitant addition of the recombinant purpurin and retinol first induced a drastic enhancement of neurite outgrowth. Furthermore, the action of retinol-bound purpurin was effective only in the control (untreated) retinas but not in those primed (treated) with a previous optic nerve transection. Thus, purpurin with retinol is the first candidate molecule of priming neurite outgrowth in the early stage of optic nerve regeneration in fish.