Thursday, May 08, 2008

Materialist Mythbusting: Genes 'R' NOT Us

"Score one for the nurture side of the nature vs. nurture debate, " says the ambitious press release from the North Carolina State University, following some of their researchers' discovery that
By studying gene expression of white blood cells in 46 Moroccan Amazighs, or Berbers – including desert nomads, mountain agrarians and coastal urban dwellers – the NC State researchers and collaborators in Morocco and the United States showed that up to one-third of genes are differentially expressed due to where and how the Moroccan Amazighs live.
The research team, which looked at the 23,000 human coding genes of members of three Amazigh groups, discovered that whether people followed urban, rural, or nomadic lifestyles significantly influenced which genes were expressed, even though members of the group had very few genetic differences. For example,
... they found respiratory genes were upregulated, or turned on, more frequently in the urban population than in the nomadic or agrarian populations. This makes sense, Idaghdour says, as urban dwellers deal with greater amounts of pollution in the city and encounter more difficulties with diseases like asthma and bronchitis. So it stands to reason that certain respiratory genes in city dwellers go into overdrive while staying quiet in rural and nomadic populations, he adds.
Anyone remember the 1997 film GATTACA? Produced in the looming shadow of the mapping of the human genome (2000), it captures the basic idea behind genetic determinism - Genes 'R' Us - and then subverts it.

In the words of David A. Kirby of Science Fiction studies at DePauw University in Indiana,

GATTACA depicts a future world in which parents are encouraged to decide the genetic makeup of their offspring before birth. In this world not everyone has access to the technology, and individuals who have not been genetically enhanced encounter severe discrimination. GATTACA’s narrative focuses on Vincent Freeman, a genetically unenhanced individual, and his interactions with three characters, Eugene, Irene, and Anton, who are genetically enhanced. During the course of the film, Vincent avoids genetic discrimination by passing off Eugene Morrow’s genetic makeup as his own. Because everyone believes that Vincent has Eugene’s genetic profile, he is able to obtain a job at the prestigious Gattaca corporation, which arranges offworld expeditions. ... Early in the film an executive is murdered at Gattaca, and the subsequent investigation is conducted by Vincent’s genetically augmented younger brother, Anton. A stray eyelash provides DNA evidence, making Vincent the prime suspect in the murder.
But GATTACA assumes that determination to succeed is the only thing that eventually enables Freeman to overcome his handicap ("There is no gene for the human spirit"). The handicap itself is viewed as fixed and irrevocable. In a scene near the movie's opening, a health technician informs Freeman's parents that, among other things, he will die in his late twenties, due to a heart defect. There it is, his whole fate, just like a sum drawn correctly on a chalkboard ...

That conventional view of the future of genetics has been widely disseminated in popular media, but recent research, like this North Carolina State study, has dealt some serious blows. As the study illustrates, genes must be expressed in order to be effective, and environment and lifestyle play a role in how they are expressed. Determination to succeed plays a key role in humans, to be sure, but the "Freemen" of the world will doubtless be glad to discover that they have other heavy hitters on their team as well.

Abstract, citation, paper, and other resources

Abstract: The different environments that humans experience are likely to impact physiology and disease susceptibility. In order to estimate the magnitude of the impact of environment on transcript abundance, we examined gene expression in peripheral blood leukocyte samples from 46 desert nomadic, mountain agrarian and coastal urban Moroccan Amazigh individuals. Despite great expression heterogeneity in humans, as much as one third of the leukocyte transcriptome was found to be associated with differences among regions. Genome-wide polymorphism analysis indicates that genetic differentiation in the total sample is limited and is unlikely to explain the expression divergence. Methylation profiling of 1,505 CpG sites suggests limited contribution of methylation to the observed differences in gene expression. Genetic network analysis further implies that specific aspects of immune function are strongly affected by regional factors and may influence susceptibility to respiratory and inflammatory disease. Our results show a strong genome-wide gene expression signature of regional population differences that pesumably include lifestyle, geography, and biotic factors, implying that these can play at least as great a role as genetic divergence in modulating gene expression variation in humans.

Citation: "A Genomewide Gene Expression Signature of Environmental Geography in Leukocytes of Moroccan Amazighs" by Youssef Idaghdour and Greg Gibson, North Carolina State University; John D. Storey, Princeton University; and Sami J. Jadallah, HRH Prince Sultan International Foundation for Conservation and Development of Wildlife, Agadir, Morocco was published April 11, 2008, in PloS Genetics.

The paper is here.

Other resources:

North Carolina State News Release

Note: Materialist myths about human origins and existence - like Genes 'R' Us - are busted weekly at Design of Life blog.


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