Correlative light and electron microscopy of early Caenorhabditis elegans embryos in mitosis

The early embryo of Caenorhabditis elegans is one of the most powerful model systems in which to study cell division. Here we have developed a correlative light and electron microscopic approach to stage early C elegans embryos prior to high-pressure freezing and electron tomography. We use cellulose microcapillaries to contain the embryos in short transparent tubes. These permit the viewing of early mitotic events under the light microscope. Using the newly developed rapid transfer system (RTS) of the Leica EMPACT2 high-pressure freezer, we have reduced the time between light microscopic observation and cryoimmobilization to about 5 sec. This correlative approach allows systematic structure-function studies in staged early wild-type embryos and those treated with RNA-mediated interference (RNAi) to reduce the level of specific gene products.