Distribution of myoplasmic cytoskeletal domains among egg fragments of the ascidian Ciona savignyi: The concentration of deep filamentous lattice in the fragment enriched with muscle determinants

Abstract

AbstractThe myoplasm of the ascidian egg contains muscle determinants and is composed of myoplasmic cytoskeletal domain (MCD). MCD consists of two interacting parts, a plasma membrane lamina (PML) and a deep filamentous lattice (DFL). We showed that, among the four types of egg fragments that are produced by centrifugation of unfertilized Ciona savignyi eggs, muscle determinants are concentrated in only one type (black fragment) and are virtually absent in the others (clear, brown and red fragments). In this study, to investigate the relationship between MCD and muscle determinants, we compared the distribution of PML and DFL among the egg fragments. Actin filament, which is a component of PML, was found in all fragments. In contrast, p58, which is a protein recognized by an anti‐intermediate filament antibody and is a component of DFL, was highly concentrated in black fragments and excluded from the other three. In addition, pigment granules and mitochondria, both of which are embedded in DFL, were also concentrated in black fragments. Thus, the distribution of muscle deteminants among the egg fragments coincided with that of DFL, supporting the possibility that muscle determinants may be associated with DFL rather than with PML. © 1995 Wiley‐Liss, Inc.