Spatial orientation of the mitotic apparatus and its stability in a polarized epithelial cell. A computer-assisted morphometric analysis.

The spatial and temporal orientation of the mitotic apparatus in reference to the polarized structure of an epithelial cell, as well as the relationship between mitotic spindle positioning and the direction of epithelial cell migration, was investigated. As an experimental model the epithelium of the mouse small intestine was chosen. Computer-assisted morphometric analysis applied in this study disclosed that the position of the mitotic spindle axis is restricted to a plane which is perpendicular to the axis of cell polarity. On this plane the spindle axis may occupy a random position. The latter finding indicates that there exists no correlation between the orientation of the mitotic spindle and the direction of epithelial cell migration. The plane of the spindle axis is established at metaphase, and no repositioning at further stages of mitosis has been observed. It is suggested that cell polarity plays a role in determination and stabilization of the mitotic spindle orientation in epithelial cells.