Identification of genetic variations associated with addictive behaviors provides a novel opportunity for using cell cultures to model molecular and cellular mechanisms that underlie addiction. The observed genetic variations have been mapped to amino acid changes in cell surface receptors, presumably affecting neuronal circuits involved in addiction behaviors. However, cellular context is likely to be important in determining the function of these genes. Construction of induced pluripotent stem cells (iPSC) from adult cells derived from drug abusing individuals carrying known genetic variants provides a means for developing physiologically relevant culture systems for understanding addiction. For the culture cell model to be useful it must not only express the affected gene but it must also provide an appropriate cellular context for studying pharmacology or cell signaling. There is no clear expectation about what type of iPSC-derived cultures would be useful in studying the cellular physiology altered by gene variants. Our hypothesis is that the altered physiology of genetic variants associated with addiction liability can be modeled in cultured neurons derived from iPSCs constructed from donor lymphocyte samples. We propose to construct several iPSC lines from donor lymphocyte samples, differentiate these iPSC into functional neurons, and then to develop methods to assay possible phenotypic differences between variant-derived cells and wild-type. These cells will be valuable for identifying cell and molecular responses to substances of abuse, to examine the effects of a known genotype on the cellular phenotype, as well as to develop novel approaches for pharmacologic intervention.
Drug abuse and addiction are a major burden to society, with the total cost of substance abuse in the U.S. exceeding $500 billion annually. Addiction is a chronic brain disease that leads to a compulsive desire for drugs despite significantly harmful consequences, including direct effects on health as well as detriments to society, including disintegration of families, child abuse, loss of employment, and a broad array of crimes. While addiction may be treatable, the discovery that some forms of addiction have an inherited component demonstrates that physiology contributes to addictive behaviors. To exploit new techniques of cellular reprogramming to prepare human neuronal cultures, we will establish induced pluripotent cell (iPSC) lines derived from donor blood samples carrying mutations in two genes known to be risk factors for addiction-an acetylcholine receptor and an opioid receptor. The blood lymphocyte samples already exist in the NIDA Center for Genomic Studies collection and will be used with permission from the collecting investigator. These iPSC will then be induced to differentiate into specific types of neurons for use in investigating the molecular bases of addiction and for screening new treatment therapies.
