Anorexia Nervosa: Genome-wide Analysis Implicates Chromosome 12

The first genetic location for anorexia nervosa has been identified in a landmark study led by UNC School of Medicine researchers. They also report there may also be metabolic underpinnings to this potentially deadly illness.

The study, conducted by the Psychiatric Genetics Consortium Eating Disorders Working Group, is the strongest genetic study of anorexia nervosa conducted to date. It included genome-wide analysis of DNA from 3,495 individuals with anorexia nervosa and 10,982 unaffected individuals.

If particular genetic variations are significantly more frequent in people with a disorder compared to unaffected people, the variations are said to be “associated” with the disorder. Associated genetic variations can serve as powerful pointers to regions of the human genome where disorder-causing problems reside, according to the National Human Genome Research Institute.

Chromosome 12

Lead investigator, Cynthia Bulik, PhD, FAED, founding director of the UNC Center of Excellence for Eating Disorders and a professor at Karolinska Institutet in Stockholm, Sweden, said:

“We identified one genome-wide significant locus for anorexia nervosa on chromosome 12, in a region previously shown to be associated with type 1 diabetes and autoimmune disorders. We also calculated genetic correlations—the extent to which various traits and disorders are caused by the same genes. Anorexia nervosa was significantly genetically correlated with neuroticism and schizophrenia, supporting the idea that anorexia is indeed a psychiatric illness.

But, unexpectedly, we also found strong genetic correlations with various metabolic features including body composition (BMI) and insulin-glucose metabolism. This finding encourages us to look more deeply at how metabolic factors increase the risk for anorexia nervosa.”

Chromosome 12 spans almost 134 million DNA building blocks (base pairs) and represents between 4 and 4.5 percent of the total DNA in cells.

Identifying genes on each chromosome is an active area of genetic research. Because researchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies. Chromosome 12 likely contains 1,100 to 1,200 genes that provide instructions for making proteins. These proteins perform a variety of different roles in the body.

The researchers are continuing to increase sample sizes and see this as the beginning of genomic discovery in anorexia nervosa. Viewing anorexia nervosa as both a psychiatric and metabolic condition could ignite interest in developing or re-purposing medications for its treatment where currently none exist.

Cynthia M. Bulik et al.
Significant Locus and Metabolic Genetic Correlations Revealed in Genome-Wide Association Study of Anorexia Nervosa
American Journal of Psychiatry, 2017; appi.ajp.2017.1 DOI: 10.1176/appi.ajp.2017.16121402

Image: Thomas Ried, NCI Center for Cancer Research, National Cancer Institute, National Institutes of Health

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