Micromanipulation of Chromosomes in Insect Spermatocytes

The micromanipulation of chromosomes has been an essential method for illuminating the mechanism for chromosome congression, the spindle checkpoint, and anaphase chromosome movements, and has been key to understanding what controls chromosome movements during a cell division. A skilled biologist can use a micromanipulator to detach chromosomes from the spindle, to reposition chromosomes within the cell, and to apply forces to chromosomes using a small glass needle with a very fine tip. While perturbations can be made to chromosomes using other methods such as optical trapping and other uses of a laser, to date, no other method allows the repositioning of cellular components on the scale of tens to hundreds of microns with little to no damage to the cell. The selection and preparation of appropriate cells for the micromanipulation of chromosomes, specifically describing the preparation of grasshopper and cricket spermatocyte primary cultures for the use in live-cell imaging and micromanipulation, are described here. In addition, we show the construction of a needle to be used for moving chromosomes within the cell, and the use of a joystick-controlled piezoelectric micromanipulator with a glass needle attached to it to reposition chromosomes within dividing cells. A sample result shows the use of a micromanipulator to detach a chromosome from a spindle in a primary spermatocyte and to reposition that chromosome within the cell.