Cortical Actin Organization in the Early Embryo Requires Folic Acid Metabolism

During early embryogenesis, nuclei divide within a syncytium without cytokinesis. However, actin-based furrows form during metaphase in order to separate neighboring nuclei. Regulation of these "metaphase furrows" has been shown to be similar to that of cytokinetic furrows. In order to find novel components or regulators of these structures, our lab has generated a class of temperature sensitive mutations that affect their formation and maintenance. One of the genes generated, ts161 (which we’ve named push pop), fails to form furrows during cycle 14  and therefore never cellularize. push pop is a homologue of the mammalian folypolyglutamate synthase (FPGS) which is an enzyme occurring early in the folate pathway. The folate pathway is required for purine synthesis and methylation of both DNA and proteins. Folate deficiencies have been shown to cause neural tube closure defects such as spina bifida. Our results indicate a possible role for folate derivatives in the organization of cytoskeletal elements. Furthermore, the folic acid pathway may in fact coordinate nuclear and cytoplasmic events during the cell cycle.