| The earliest events in embryonic development are driven and regulated by maternal products already present in the unfertilized egg. In zebrafish, Danio rerio, such maternally-driven processes include cortical granule exocytosis, cytokinesis and germ plasm segregation. A recessive maternal-effect mutation that affects these three processes, in the gene aura, was identified in a zebrafish gynogenesis-based screen. To identify and better understand normal aura function, I have characterized the aura mutant phenotype and determined the molecular identity of this gene. aura affects several events during early development that may be dependent on cytoskeletal rearrangements and it encodes MID1ip1. Cell biology, genetic, and other experimental approaches were used to characterize the aura/MID1ip1 gene function. Together, these studies will contribute to understanding the function and regulation of aura/MID1ip1 during cortical granule exocytosis, cytokinesis and germ plasm segregation.;In this study, I have contributed to the lab's investigation in the relation between the invariant cleavage pattern of the early zebrafish embryo and cortical cues by determining the localization of dynein and dynactin with respect to the centrosome and the spindle. Additionally, I have tested for defects in spindle alignment in several maternal-effect mutants that affect cell shape. These observations, together with experiments by others in the laboratory, reinforce previous findings in other organisms, that cortical cues directing spindle orientation are transduced by dynein and dynactin to position the spindle and, consequently, determine the plane of cell cleavage. |
