Abstract
Recently, we reported that purpurin is a retina-specific secretory protein and acts as a trigger molecule for axonal outgrowth during fish optic nerve regeneration. In zebrafish retinal development, although there was the highly expression of purpurin, the function of purpurin is not so clear. Here, we investigated the role of purpurin revealed by loss of function of purpurin gene using morpholino antisence oligonucleotides. During retinal development, cell cycle and neurogenesis is stringently controlled by several cues, and six types of neurons and one type of Muller glial cells were organized into distinct layers at 3 days post fertilization (dpf). However retinal lamination was not detected in purpurin morphant at 3 dpf. Muller cells were confined only inner retina and differentiation of photoreceptor and bipolar cells were not observed. Additionally, almost all retinal progenitor cells continued dividing even at 3 dpf. However, the inhibitory effect of morpholino was strictly transient, and purpurin mRNA and protein were normally detected at 5-7 dpf. At 7 dpf, we observed differentiated photoreceptor cells and bipolar cells. The visual function revealed by optomotor response was significantly retarded in purpurin morphant at 5 dpf. At 10 dpf, optomotor response was not changed between control and purpurin morphant. These results strongly indicate that purpurin is a key molecule for retinal neurogenesis in developing zebrafish. [J Physiol Sci. 2008;58 Suppl:S113]
