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

The cytoskeleton of the mammalian egg and early embryo is highly unique when compared to the cytoskeleton of their somatic cell brethren. Although all three cytoskeletal systems, actin filaments, microtubules, and intermediate 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 demands of the developmental process. The major demands placed upon eggs and embryos are developmental transitions (i.e., fertilization, compaction, blastocyst formation, germ layer formation and gastrulation), each of which must be traversed in order for the embryo to form a new individual. To successfully complete all of the necessary processes during early development, eggs and embryos must call upon many signal transduction mechanisms, cytoskeletal components, and genes that are both unique to embryogenesis and ubiquitous among many types of somatic cells. It is the goal of this review to provide some current details into the mechanisms that drive early development primarily focusing on the cytoskeletal components eggs and embryos have adapted to promote embryogenesis.