Patterns of ciliary retraction in echinoid embryos.

Abstract

In this study sea urchin embryos were used to investigate how cilia are disassembled and to investigate the role that cilia play in cell division. A retraction mechanism was proposed in which the ciliary axoneme is entirely withdrawn into the cell cytoplasm before it is completely disassembled. This mechanism may be mediated by a cortically-localized, plus-end directed motor protein. To determine biochemical distributions of the axoneme and mitotic spindle, a ratiometric imaging technique was developed. Analysis of ratiometric images suggests that the axoneme is destabilized by a deacetylase enzyme which may function to regulate the levels of alpha-tubulin and acetylated tubulin present in the mitotic spindle. The use of ratiometric imaging will be useful for future experiments that investigate the role of other post-translational modifications to tubulin. This study reports the identification of two distinct retraction modes which appear to be independent of cilia subtype or length.