The cytoskeleton and cytomusculature in embryogenesis--an overview.

The role of microfilaments and microtubules comprising the cytoskeleton and cytomusculature in embryonic development is discussed. The cytomusculature, as microfilaments, is evident in both the unfertilized and fertilized egg and probably plays a role in sperm incorporation, cortical contractions, and cytokinesis. The cytoskeleton, in the form of microtubules, appears after fertilization in the form of the sperm aster and the mitotic apparatus. The cytoskeleton and cytomusculature play a decisive role in shape changes of individual cells responsible for gastrulation, neurulation, and morphogenesis of other epithelial sheets. Several developmental defects, such as spina bifida, may be related to malfunctioning of the cytoskeleton or cytomusculature. The putative role of microfilaments and microtubules in cell shape changes during embryogenesis can best be, at least initially, inferred from careful ultrastructural observations.