A GENE TRAP STRATEGY FOR IDENTIFYING THE GENE EXPRESSED IN THE EMBRYONIC NERVOUS-SYSTEM

An efficient gene trap strategy was devised for identifying the genes that are expressed in the mouse developing nervous system. Mouse embry onic stem (ES) cell lines that carried independent integrations of a g ene trap vector, pSneolNlacZA, were allowed to differentiate in a susp ension culture system. To select cells containing neurons, astrocytes or neuron-glia precursors, cell lines were immunohistochemically exami ned with antibodies against neuron-specific proteins (neurofilament pr otein 150 kD and microtubule associated protein 2), glial fibrillary a cidic protein or nestin. Three cell clones (GT3-8, 11 and 12) were imm unoreactive to either of the antibodies employed and at the same time positive for beta-galactosidase activity. When chimeric embryos were g enerated by the use of the above 3 cell lines, some cells in their ner vous system showed X-gal staining. Thus the major advantage of the pre sent gene trap method lies in its prescreening step of manipulated ES cells prior to generation of chimeric animals. This method holds promi se as a useful tool for investigating the genes involved in the develo pment of the nervous system.