Abstract
Abstract: :
Purpose: The vertebrate retina develops from proliferating neuroepithelial cells. During the process of retinal lamination, correct cell fate and position (migration) decisions are essential. The zebrafish heart and soul (has) mutation shows disrupted retinal lamination. Mutations in the signaling molecule atypical Protien Kinase C λ (PKCλ) are responsible for the has phenotype [Peterson Curr Biol. 11:1481 (2001); Horne–Badovinac Curr Biol. 11:1492 (2001)]. In neuroepithelia and photoreceptors, PKCλ is a component of an apically localized multi–protein complex which is an essential regulator of cell polarity. To better understand PKCλ in retinal development, we have investigated zebrafish with a null mutation in has/PKCλ. Methods: Retinal cell type positioning was analyzed by immunofluorescence in wild type and has mutant zebrafish. Brdu labeling followed by immunostaining with ganglion cell makers was conducted to further investigate positioning defects of the first differentiated cell type in retinal development. Finally, genetic mosaic experiments were conducted to assess the cell autonomy of PKCλ signaling during cell type positioning and photoreceptor development. Results: Cell type maker analysis revealed positioning defects for multiple cell types including early and late born cells. Brdu labeling revealed that mis–positioned ganglion cells were born at the appropriate time in development, suggesting post–mitotic cell migration, but not cell fate decisions are altered in has mutants. Surprisingly, genetic mosaic analysis showed cell type positioning defects are non–cell–autonomous for has mutants. Conversely, has functions cell–autonomously during photoreceptor development. Conclusions: PKCλ signaling regulates multiple steps during retinal development. PKCλ signaling is required for overall retinal patterning as has mutants show cell positioning defects. Positioning defects of ganglion cells are due to altered post–mitotic cell migration and not cell fate errors. Cell type positioning is non–cell–autonomous for has mutants suggesting PKCλ signaling regulates additional secreted factor(s) essential for proper retinal migration. Subsequent analysis, however, revealed a cell–autonomous requirement for PKCλ during photoreceptor development.
Keywords: retinal development • signal transduction • cell–cell communication