Mutant gene linked to obsessive compulsive disorder

October 23, 2003

Analysis of DNA samples from patients with obsessive compulsive disorder (OCD) and related illnesses suggests that these neuropsychiatric disorders affecting mood and behavior are associated with an uncommon mutant, malfunctioning gene that leads to faulty transporter function and regulation. Norio Ozaki, M.D., Ph.D., and colleagues in the collaborative study explain their findings in the October 23 Molecular Psychiatry.

Researchers funded by the National Institutes of Health have found a mutation in the human serotonin transporter gene, hSERT, in unrelated families with OCD. A second variant in the same gene of some patients with this mutation suggests a genetic "double hit," resulting in greater biochemical effects and more severe symptoms. Among the 10 leading causes of disability worldwide, OCD is a mental illness characterized by repetitive unwanted thoughts and behaviors that impair daily life.

"In all of molecular medicine, there are few known instances where two variants within one gene have been found to alter the expression and regulation of the gene in a way that appears associated with symptoms of a disorder," said co-author Dennis Murphy, M.D., National Institute of Mental Health (NIMH) Laboratory of Clinical Science. "This step forward gives us a glimpse of the complications ahead in studying the genetic complexity of neuropsychiatric disorders."

Psychiatric interviews of the patients' families revealed that 6 of the 7 individuals with the mutation had OCD or OC personality disorder and some also had anorexia nervosa (AN), Asperger's syndrome (AS), social phobia, tic disorder, and alcohol or other substance abuse/dependence. Researchers found an unusual cluster of OCD, AN, and AS/autism, disorders together with the mutation in approximately one percent of individuals with OCD.

The scientists analyzed DNA from 170 unrelated individuals, including 30 patients each with OCD, eating disorders, and seasonal affective disorder, plus 80 healthy control subjects. They detected gene variants by scanning the hSERT gene's coding sequence. A substitution of Val425 for Ile425 in the sequence occurred in two patients with OCD and their families, but not in additional patients or controls. Although rare, with the I425V mutation found in two unrelated families, the researchers propose it is likely to exist in other families with OCD and related disorders.

In addition to the I425V mutation, the two original subjects and their two siblings had a particular form of another hSERT variant, two long alleles of the 5-HTTLPR polymorphism. This variant, associated with increased expression and function of the serotonin transporter, suggests a "double hit," or two changes within the same gene. The combination of these changes, both of which increase serotonin transport by themselves, may explain the unusual severity and treatment resistence of the illnesses in the subjects and their siblings.

"This is a new model for neuropsychiatric genetics, the concept of two or maybe more within-gene modifications being important in each affected individual. This is also probably the first report of a modification in a transporter gene resulting in a gain rather than a decrease in function," said NIMH Director Thomas Insel, M.D.

SERT allows neurons, platelets, and other cells to accumulate the chemical neurotransmitter serotonin, which affects emotions and drives. Neurons communicate by using chemical messages like serotonin between cells. The transporter protein, by recycling serotonin, regulates its concentration in a gap, or synapse, and thus its effects on a receiving neuron's receptor.

Transporters are important sites for agents that treat psychiatric disorders. Drugs that reduce the binding of serotonin to transporters (selective serotonin reuptake inhibitors, or SSRIs) treat mental disorders effectively. About half of patients with OCD are treated with SSRIs, but those with the hSERT gene defect do not seem to respond to them, according to the study.

Any vulnerability to OCD from gene effects most likely interacts with events in the environment like stresses, other factors like gender, and treatments, Murphy said. By examining the serotonin transporter gene's mutation and flawed regulation in individuals with OCD, the new research provides insights on transporter function and on the consequences of the variant, which may lead to tests to identify and treat mental illness.

A related study in the August 2003 Molecular Pharmacology tested consequences of the hSERT variant. The report is considered the first to identify a coding mutation in a transporter linked to a psychiatric condition. Researchers found that the I425V mutation of hSERT increased the transport activity of this protein, capturing more serotonin and most likely reducing effects at the receiving neuron's receptors, outperforming the common transporter. The mutant molecule was not regulated normally and did not respond to cell signals that activate the common form of the transporter. Gary Rudnick and Fusun Kilic, Yale University School of Medicine, with Murphy at NIMH, conducted this research, which was funded by the Rockefeller Brothers Fund, the National Alliance for Research on Schizophrenia and Depression, and the National Institute on Drug Abuse (NIDA).

Participants in the study published in Molecular Psychiatry were: Norio Ozaki, Fujita Health University School of Medicine, Toyoake, Aichi, Japan, whose early work on the project was supported by awards from the NIMH Intramural Programs of the National Institute of Alcohol Abuse and Alcoholism (NIAAA) and the NIMH; David Goldman, NIAAA; Walter Kaye and Katherine Plotnicov, University of Pittsburgh Medical Center and Western Psychiatric Institute and Clinic; Benjamin Greenberg, Butler Hospital and Brown University School of Medicine; Jaakko Lappalainen, Yale University School of Medicine; and Gary Rudnick, Department of Pharmacology, Yale University School of Medicine; Dennis Murphy, NIMH Laboratory of Clinical Science.
-end-
NIMH, NIDA, and NIAAA are part of the National Institutes of Health (NIH), the Federal Government's primary agency for biomedical and behavioral research. NIH is a component of the U.S. Department of Health and Human Services.

NIH/National Institute of Mental Health

Related Mental Health Articles from Brightsurf:

Mental health strained by disaster
A new study found that suicide rates increase during all types of disasters -- including severe storms, floods, hurricanes and ice storms -- with the largest overall increase occurring two years after a disaster.

The mental health impact of pandemics for front line health care staff
New research shows the impact that pandemics have on the mental health of front-line health care staff.

World Mental Health Day -- CACTUS releases report of largest researcher mental health survey
On the occasion of 'World Mental Health Day' 2020, CACTUS, a global scientific communications company, has released a global survey on mental health, wellbeing and fulfilment in academia.

Mental illness, mental health care use among police officers
A survey study of Texas police officers examines how common mental illness and mental health care use are in a large urban department.

COVID-19 outbreak and mental health
The use of online platforms to guide effective consumption of information, facilitate social support and continue mental health care delivery during the COVID-19 pandemic is discussed in this Viewpoint.

COVID-19 may have consequences for mental health
The COVID-19 pandemic appears to be adversely affecting mental health among hospitalised patients, the healthcare professionals treating them and the general population.

Mental health outcomes among health care workers during COVID-19 pandemic in Italy
Symptoms of posttraumatic stress disorder, depression, anxiety and insomnia among health care workers in Italy during the COVID-19 pandemic are reported in this observational study.

Mental ill health 'substantial health concern' among police, finds international study
Mental health issues among police officers are a 'substantial health concern,' with around 1 in 4 potentially drinking at hazardous levels and around 1 in 7 meeting the criteria for post traumatic stress disorder and depression, finds a pooled data analysis of the available international evidence, published online in Occupational & Environmental Medicine.

Examining health insurance nondiscrimination policies with mental health among gender minority individuals
A large private health insurance database was used to examine the association between between health insurance nondiscrimination policies and mental health outcomes for gender minority individuals.

Mental health care for adolescents
Researchers examined changes over time in the kinds of mental health problems for which adolescents in the United States received care and where they got that care in this survey study with findings that should be interpreted within the context of several limitations including self-reported information.

Read More: Mental Health News and Mental Health Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.