Early defects in photoreceptor outer segment morphogenesis in zebrafish ift57, ift88 and ift172 Intraflagellar Transport mutants

Intraflagellar Transport (IFT) refers to a highly conserved process occurring in eukaryotic ciliated structures. In vertebrate photoreceptors, IFT mediates protein trafficking to the outer segments. The IFT particle is a multi-subunit complex and mutations in many individual components causes photoreceptor defects. In zebrafish, mutations in the ift57, ift88, and ift172 genes result in retinal degeneration by 5 days post fertilization (dpf). Although the effects of these mutations on photoreceptor survival have been described, early developmental morphogenesis remains poorly understood. We used transmission electron microscopy and immunohistochemistry to examine these mutants at 60, 72, and 96 h post fertilization (hpf) and describe early photoreceptor morphogenesis defects.