Genome-based drug discovery: prioritizing disease-susceptibility/disease-associated genes as novel drug targets for schizophrenia.

The search for new classes of antipsychotics based on novel targets identified from linkage/linkage association in diseased cohorts and microarray approaches using tissue from affected individuals is a high priority in central nervous system research. Genes linked to schizophrenia, a disease affecting 1% of the population, have been identified on nearly every chromosome of the human genome leading to a diverse choice of targets for validation. Interestingly, while the majority of currently used antipsychotic medications act by blocking dopamine receptors, there have been few genetic studies implicating the dopamine receptor family in disease etiology. Recently, four genes have been identified that encode dysbindin, neuroregulin, D-amino acid oxidase and G72, respectively, that support previous studies suggesting that schizophrenia may result from a hypofunction of glutamatergic neurotransmission. Linkage and microarray studies have similarly supported studies implicating the alpha 7 neuronal nicotinic receptor in the etiology of schizophrenia. Microarray studies using brain tissue from schizophrenic patients have shown changes in gene expression that number in the thousands, involving a number of proteins related to synaptic structure and function (PSYN gene group) and cellular metabolism. The majority of these proteins are not traditional drug discovery targets, nor are their functional roles in schizophrenia obvious, providing a challenge to validate them from the drug target identification/drug discovery perspective. The current state-of-the-art in genome-based approaches to schizophrenia, target discovery highlights a need for a multidisciplinary, integrative, null hypothesis-based approach to sort through these novel genes as drug targets.