Cancer can be viewed as a genetic disorder, with tumor suppressor genes acting recessively and oncogenes acting dominantly. In order to understand the contribution of genes to the progression of cancer, the genome of cell lines or animal models can be genetically engineered to alter the phenotype. Traditionally, with oncogenes, they are overexpressed in gain-of-function studies, while tumor suppressor genes are eliminated in loss-of-function studies.
Knockout animals have a global deletion of the gene of interest in all cells. However, in about 15% of gene knockouts, this gives rise to a lethal phenotype where the animal dies during gestation. In this case, it is warranted to perform a tissue-specific knockout in the tissue or organ of interest in order to avoid the lethal phenotype.
If you are studying the effects of the loss of a tumor suppressor gene in the brain, which of the following techniques would you use?