Our laboratory is interested in the molecular and genetic bases of complex brain disorders, including genetic predisposition for alcoholism and drug abuse, and molecular mechanisms underlie such neuro-sensory processes as stress, neuropathic pain, and pain-relief analgesia.
Regarding genetic predisposition for alcoholism and drug abuse, we have carried out human genetic studies with a focus on genetic variations in human populations, especially those with potential impact on physiological function and behavior. This is based on the belief that human genetics is for the most part about small, subtle functional polymorphisms that underlie individual differences in physiology and disease vulnerability. One example is a prevalent genetic variation in the mu opioid receptor that we have studied. This small genetic polymorphism only changes one base pair in the gene, thus is a SNP (single nucleotide polymorphism), giving rise to the subtle variation of a single amino acid. Recent studies from other investigators have shown that this SNP is associated with functional consequences in humans, including predisposition to opioid dependence, differential stress hormone response to opioid antagonist challenge, and potential impact on treatment outcome for alcoholism, nicotine dependence, and Parkinson disease pharmacotherapy.
A related direction we are undertaking is to investigate genetic mediators of complex brain disorders, utilizing SNP and other genetic variations as informative markers, to track gene-behavior correlations. As an example, we are conducting a SNP genotyping project using a well-characterized sample set that has been collected and subjects followed over twenty years, to determine potential association between relevant genetic factors and cellular functions on one hand, and alcohol usage and risk behaviors on the other. By systematically examining the genetic pathways that subserve the neurobiological mechanisms, we hope to advance our knowledge in the genetic factors contributing to disease process, so as to provide useful information for developing effective therapeutic interventions.
Chronic pain from nerve injury is rather common, and represents a major public health problem. For people who suffer neuropathic pain, current treatment options are woefully inadequate. To develop more effective therapeutic approaches, it is important to understand the mechanistic basis for neuropathic pain, so that molecular targets can be identified for exploring medication development and/or other types of interventions. Using a molecular genetic strategy, we have identified a number of genes that participate in neuropathic pain. When we inhibited the activity of these genes, the pain from nerve damage is alleviated. We also discovered that it is possible to completely block the chronic pain from developing in the rodent models by inhibiting nerve transduction during a specific time window. We are conducting further research to advance our knowledge on how genes are involved in chronic pain, as well as the mechanisms of analgesia from drugs such as opioids.
In recent years, epidemiology studies indicate that there are genetic factors common to a variety of compulsive behaviors, including alcoholism, compulsive video gaming, pathological gambling, and other forms of impulsivity/compulsivity display. To better understand the molecular basis for such diverse behaviors with a common theme of compulsive nature, we are beginning an effort to bridge several rodent models of compulsive behaviors, and to look for shared molecular components that may underlie these behaviors. One example is a mouse model of alcohol consumption. Given the opportunity, some mice drink more alcohol than other mice, just like individual differences in human when alcohol is concerned. Interestingly, when the availability of alcohol is restricted, some mice exhibit a compulsive tendency to drink more alcohol whenever they can, suggesting an innate drive toward excessive alcohol consumption. What might the biological, or molecular, basis be for these mice to drink more alcohol than other mice? We have began comparing genetic differences among these mice, in an effort to put together pieces of the genetic puzzle that may lead to revelation of the root cause in molecular level regulation of behavioral impulse. Currently, two approaches are underway: gene activity profiling to determine what genes more actively contributing to excessive alcohol drinking behavior, and micro-RNA profiling to examine specific micro-RNA as 'master regulators' for concerted gene expression regulation. Our objective is to unearth candidate genes with a high likelihood of playing 'master switch' for behavior pattern, and to conduct in vivo interference studies for pinpointing the specific role of key genes.