Kathleen R. Foltz
Research in our laboratory is focused on elucidating the molecular mechanisms of gamete recognition, binding and subsequent egg activation. After contact of the sperm with the proper egg, the two cells fuse, the fertilized egg is "activated’ and the developmental pathway is initiated. Both large-scale biochemical approaches as well as single cell (microinjection and imaging) experiments can be conducted easily using the eggs of marine invertebrate (especially echinoderm) species, which share the basic aspects of egg activation with other species, including mammals. Our current focus is on the molecular basis of egg activation and in particular, the elucidation of the signaling components that lead to the initiation of Ca2+ release at fertilization. We also have initiated an investigation of the downstream effectors that mediate entry into the first cell cycle, focusing primarily on entry into S-phase. In both starfish and sea urchin eggs, it appears that an egg tyrosine kinase, most-likely a member of the Src family, is activated at fertilization and subsequently activates PLC-g , generating IP3 and thus initiating Ca2+ release through IP3 receptors in the endoplasmic reticulum. Among other things, this Ca2+ release leads to inactivation of MAP kinase and initiation of DNA synthesis. We hope to be able to construct detailed signal transduction pathways that lead from the sperm binding and fusion at the egg plasma membrane to the various outputs of egg activation.