Background - The molecular- and cellular-based mechanisms that contribute to the initiation and development of addiction remain to be elucidated. Estimates have suggested that 40-60 percent of the vulnerability to addiction may be attributable to genetic aberrations. Multiple chromosomal regions have been linked to addiction including those containing the dopamine transporter (DAT) and vesicular monoamine transporter (VMAT2) genes. Current efforts to understand how polymorphisms in these monoamine transporters contribute to the molecular mechanisms of addiction are severely hindered by the inability to directly interrogate neural cell types from the patients. There is great potential for patient-specific iPS cell technology to profoundly impact our understanding of human development and disease by providing genetically distinct, functional sources of human cells.
Objective - The objective of the research is to develop a cell-based system whereby neural cells from afflicted individuals can be functionally assayed to interrogate the molecular mechanisms underlying addiction.
Study population Controls (non-drug users) and opioid dependent adults receiving opioid agonist therapy aged 21- 65 will be enrolled.
Design Participants demographic characteristics, psychosocial evaluation, and psychiatric, medical, and drug use histories will be characterized. DNA will be collected via cheek swabs of up to 30 potential participants for determination of dopamine transporter (DAT) and vesicular monoamine transporter (VMAT2) gene polymorphisms. Participants (N=16) with suitable polymorphisms will be asked to under go skin biopsies; 2 individuals for each of two genotypes for each gene (DAT or VMAT), i.e., 8 samples from addicts and 8 samples for control subjects. Collaborators at Case Western Reserve University will use the skin cells to derive and characterize patient-specific, induced pluripotent stem (iPS) cells that carry monoamine transporter polymorphisms for the hDAT1 and hVMAT2 genes. They will differentiate patient-specific iPS cells line into dopaminergic neurons and carry out a detailed and functional characterization of these cells to identify their molecular characteristics.
Outcome measures - Biological specimens from the addiction patients and controls will be used to derive and characterize patient-specific, induced pluripotent stem (iPS) cells that carry monoamine transporter polymorphisms. Patient-specific iPS cells lines will be differentiated into dopaminergic neurons. In follow up studies, we will characterize, compare, and functionally assay these patient-specific, iPS cell-derived dopaminergic neurons from control and addiction patients that carry polymorphisms for hDAT1 and hVMAT2 gene to investigate any possible association with dopamine neurotransmission variations and vulnerability to addiction.
