The identification and validation of disease-causing target genes is an essential first step in drug discovery and development.
            Genomics and proteomics technologies have already begun to uncover novel functional pathways and therapeutic targets in several
            human diseases such as cancers and autoimmunity. Also, bioinformatics approaches have highlighted several key targets and
            functional networks. In contrast to gene-profiling approaches, phenotype-oriented target identification allows direct link
            between the genetic alterations and a disease phenotype. Therefore, identified genes are more likely to be a cause rather
            than a consequence of the disease. Once a gene target or a mechanistic pathway is identified, the next step is to demonstrate
            that it does play a critical role in disease initiation, perpetuation, or both. A range of strategies exists for modulating
            gene expression in vitro and in vivo. These strategies include the use of antibodies, negative dominant controls, antisense
            oligonucleotides, ribozymes, and small-interfering RNAs. In contrast to in vitro assays, mouse reverse genetics such as knockout
            phenotypes has become a powerful approach for deciphering gene function and target validation in the context of mammalian
            physiology. In addition to disease-causing genes, the identification of antigens that stimulate both arms of the immune system
            is the major goal for effective vaccine development. The hope is that target discovery and validation processes will concurrently
            identify and validate therapeutic targets for drug intervention in human diseases.