Composition, regulation, and function of the cytoskeleton in mammalian eggs and embryos

The cytoskeleton of the mammalian egg and early embryo is highly unique whe n compared to the cytoskeleton of their somatic cell brethren. Although all three cytoskeletal systems, actin filaments, microtubules, and intermediat e filaments, are present as early as the unfertilized egg; each system has adapted features that allow the egg and early embryo to meet the strict dem ands of the developmental process. The major demands placed upon eggs and e mbryos are developmental transitions (i.e., fertilization, compaction, blas tocyst formation, germ layer formation and gastrulation), each of which mus t be traversed in order for the embryo to form a new individual. To success fully complete all of the necessary processes during early development, egg s and embryos must call upon many signal transduction mechanisms, cytoskele tal components, and genes that are both unique to embryogenesis and ubiquit ous among many types of somatic cells. It is the goal of this review to pro vide some current details into the mechanisms that drive early development primarily focusing on the cytoskeletal components eggs and embryos have ada pted to promote embryogenesis.