While many aspects of mitosis and cytokinesis have been elucidated, a vast amount of ongoing work focuses on these fundamental processes showing that much remains for discovery and resolution. Advances in microscopy and immunocytochemistry and techniques for the mechanical, optical and biochemical manipulation of cells and their components have traditionally led and continue to lead to substantial progress in this field. Valles and coworkers recently discovered that early cleavages (cell divisions) of embryos of the frog, Xenopus laevis, align with a large static magnetic field. The reorientation of cleavages depends systematically on field strength and orientation and does not depend on field gradients. This novel discovery presents opportunities for dissecting interactions between cells and magnetic fields and potentially developing a new tool for manipulating cells and studying cell division. The two specific objectives address these opportunities.
Specific Objective 1: Determine the cleavage plane reorientation mechanism- While some systematics of this effect have been established, the mechanism has not. To achieve this goal, they will subject sets of frog embryos to magnetic fields during different periods of their cell cycle to identify when the influence of the magnetic field is strongest. They will use immunocytochemistry and confocal microscopy techniques to image the orientation and morphology of the microtubules of embryos exposed to the magnetic field to determine the influence of the magnetic field.
Specific Objective 2: Determine whether microtubules in vivo align with a magnetic field -Cellular structures that are likely to be involved in the reorientation by magnetic field are those composed of microtubules. Microtubules comprise a major portion of the mitotic apparatus and recent measurements have shown that individual microtubules align in vitro in a magnetic field. Because of the importance of microtubules to the cleavage plane reorientation effect and to many other cell processes, the second goal is to image the microtubules in magnetic field exposed frog embryos to discern whether or not they are tending to align with the field direction. Immunocytochemistry and confocal microscopy techniques will be used to image the astral microtubules in field exposed, Xenopus embryos and compare the observed microtubule shapes to those calculated using the known properties of microtubules. If the microtubules do align then the possibility exists that other microtubule dependent cell processes can be manipulated with magnetic fields. If they do not, then the microtubules in living systems have properties that differ from their in vitro counterparts. Examining the source of such differences can provide insight into in vivo processes.
Together, these experiments should provide fundamentally new insight into the interactions between magnetic fields and matter that might lead to general rules about those interactions and the potential for "magneto-manipulation" as a viable research tool.
This project is jointly supported by the Cell Biology Program in the Division of Molecular Biosciences, Directorate for Biological Sciences (BIO) and the Office of Multidisciplinary Activities (OMA) in the Directorate for Mathematical and Physical Sciences (MPS).
