MedicalResearch.com Interview with: Hyun Ji Noh PhD Computational Scientist, Medical and Population Genetics Broad Institute of MIT and Harvard MedicalResearch.com: What is the background for this study? What are the main findings? Response: Obsessive-compulsive disorder (OCD) is a debilitating neuropsychiatric disorder, characterized by intrusive thoughts and repetitive behaviors. OCD is estimated to affect roughly 80 million people worldwide, but its neurobiology remains poorly understood. To understand the disorder’s underpinnings, we searched for genetic mutations that are associated with OCD. For this, we first identified 608 genes that were most likely to be important  in OCD - some that have previously been identified in OCD-like behaviors in dogs and mice, and others in human autism, which also involves repetitive behaviors. We compared these genes in 592 people with OCD and 560 people without OCD, and found that 4 of these genes were significantly different between people with and without OCD: NRXN1, HTR2A, CTTNBP2 and REEP3. All of these four genes have important functions in the brain. Specifically, we found that the variants in NRXN1 are likely to change its ability to bind other synaptic proteins. Synaptic proteins link neurons together, and are critical for transmitting signals through the brain. We also found that the variants in CTTNBP2 and REEP3 don’t actually change the proteins made by these genes, but instead probably affect gene regulation (for example, how much of the protein is made). These ‘regulatory’ variants disrupt the binding of transcription factors (proteins that regulate expression of genes in the body) near the gene. (more…)