Searching for Genetic Link to Anorexia nervosa
Is there an answer yet?

Introduction:
Anorexia nervosa is an eating disorder that mostly affects young women.
Patients with Anorexia show excessive restriction on eating,
see themselves as fat when actually underweight
and damage their heart muscles and bones by starvation.
Anorexia is extremely difficult to treat, kills up to 20% of the affected (Roan, 2003).
Another eating disorder often associated with Anorexia is Bulimia nervosa,
which causes affected individuals to go through cycles of binge-eating and compensatory behaviors,
such as starvation, self-induced vomitting and laxative abuse.
We are surrounded by popular media that glamourizes the Hollywood life style,
and by the ideal body image portrayed on magazine covers and television shows.
So, why do some girls take the subliminal message more seriously than others?
Can there be a genetic cause to a socio-cultural disease, Anorexia nervosa?
I have found that some popular press did a better job than others
at reporting what the scientists have found concerning the above questions.
I have also investigated on how the scientists did the research,
and what the most current biological databases say about the genetic link to Anorexia.

Popular Press:
Los Angeles Times
Seeking a genetic link to anorexia nervosa;
U.S. launches study of families with two or more sufferers of the mysterious and sometimes deadly eating disorder
This article gives a nice account of what Anorexia nervosa is, and emphasizes that
not just one gene causes this disease, but there may be some common genes that
Anorexia sufferers share. It does not jump to any conclusions, but only mentions that chromosome 1
seems to be a key player in this disease. I was pleased to note that the article did not
give speculations for cures or hopeful promises of genetic treatment for Anorexia nervosa.

CNN
Research could shed light on eating disorders
This article suggests that eating disorders such as Anorexia and Bulimia
may be caused by an autoimmune disorder, that some proteins that usually help the body
fight foreign invaders might be attacking normal body processes such as
maintaining body weight. This article claims that a group of scientists studied 57 women
who had eating disorders, and that they found antibodies in their blood
that disrupted their normal food intake. It also suggested that drugs that treat
the regulation of the antibodies might cure Anorexia and Bulimia.
This article helps people understand that a psychiatric disorder such as Anorexia
could have a significant biological cause in addition to strenuous environmental factors.
However, the conversation shown in this article seems to oversimplify the disease,
and might mislead the readers to think that the cure for Anorexia is in near future.


Scientific Publication:
American Journal of Human Genetics
Evidence for a susceptibility gene for Anorexia Nervosa on Chromosome 1
Dr. Grice and his colleagues first investigated 192 families who included
at least one case of Anorexia or Bulimia nervosa, but found only a weak linkage on chromosome 4.
However, when they narrowed the genomewide search to the subset of 37 families
who included at least two cases of strictly Anorexic patients without the self-vomitting symptoms of Bulimia,
they found a statistically significant location on chromosome 1p that might indicate
individuals who are susceptible to Anorexia nervosa (Grice et al., 2002).

Human Molecular Genetics
Linkage analysis of anorexia nervosa incorporating behavioral covariates
Dr. Devlin and his colleagues explored linkage between behavioral traits and gene loci.
They had two behavioral covariates that accompanied the individuals diagnosed with Anorexia:
drive-for-thinness and obsessionality. They studied 196 families that included affected sibling
or relative pairs, and searched the genome with 387 short tandem repeat markers.
They found three different loci that gave statistically significant results: one on chromosome 1,
another on chromosome 2, and the last on chromoseom 13 (Devlin et al. 2002).

National Center for Biotechnology Information (NCBI) says that
the official gene symbol and name have not yet been determined,
and the interim name used for this locus is ANON: susceptibility to Anorexia nervosa.
The locus ID used in NCBI is 171514, and the marker used
to identify this region of chromosome 1 is called D1S3721.
The working draft nucleic acid sequence information can be found here.
No functional protein for this gene could yet be found on PDB.
Gene Map locus: Susceptibility to Anorexia Nervosa
Online Mendelian Inheritance in Man: Information on AN gene


Figure 1. Illustration of chromosome 1 and the location of susceptibility to Anorexia Nervosa gene.
Image taken from NCBI human map viewer.

Is there an answer yet?
Considering the fact that the researchers do not even have an official name
for the "Anorexia" gene on chomosome 1, I know that more news will follow from current research.
LA Times has been cautious in announcing what the researchers have found so far,
but CNN seems to have oversimplified the complexity involved in eating disorders.
But the idea that genetic factors could play significant roles in a socio-cultural disorder
is definitely worth the investigation, and will provide footsteps to more effective treatment in the future.


References:
Devlin, B.; Bacanu, S.-A.; Klump, K. L.; Bulik, C. M.; Fichter, M. M.; Halmi, K. A.; Kaplan, A. S.; Strober, M.; Treasure, J.; Woodside, D. B.; Berrettini, W. H.; Kaye, W. H. :
Linkage analysis of anorexia nervosa incorporating behavioral covariates. Hum. Molec. Genet. 11: 689-696, 2002.

Grice, D. E.; Halmi, K. A.; Fichter, M. M.; Strober, M.; Woodside, D. B.; Treasure, J. T.; Kaplan, A. S.; Magistretti, P. J.; Goldman, D.; Bulik, C. M.; Kaye, W. H.; Berrettini, W. H. :
Evidence for a susceptibility gene for anorexia nervosa on chromosome 1. Am. J. Hum. Genet. 70: 787-792, 2002.

Roan, S.: Seeking a genetic link to anorexia nervosa;
U.S. launches study of families with two or more sufferers of the mysterious and sometimes deadly eating disorder. Los Angeles Times: April 7, 2003. LexisNexis Academic Link to this article

"Research could shed light on eating disorders". CNN health. 10 December 2002.
http://www.cnn.com/2002/HEALTH/conditions/12/10/otsc.anorexia.antibodies/index.html

This web page was produced as an assignment for an undergraduate course at Davidson College.