There are two scientific studies about which I've been thinking lately, both in some way having to do with genes, behavior and the environment. Ironically, the public debate on this topic bores me, mostly because the most vocal participants in the debate over-generalize and tend to be completely ignorant on the topic of which they nevertheless speak. On the other hand, scientific studies that address specific questions on the topic interest me greatly.

In one study published in Nature (Manoli et al., Nature 2005 Jul 21;436(7049):395-400), the manipulation of a single gene in a subset of neurons in fruit flies dramatically changed mating behavior. The other study was published two years ago in Nature Neuroscience (Weaver et al., Nat Neurosci. 2004 Aug;7(8):847-54) and was closer to my field of thesis work. The authors found that differences in mothering styles in rats affected molecular modifications at a specific gene in the pups. The changes found at the molecular level lasted into adulthood and affected the responses of these rats (as adults) to stress.

The first study is exciting because a complex behavior is drastically altered by mutating only one gene. (Incidentally, this conclusion is where I fear the public debaters misconstrue and over-generalize. The study addresses the role of one particular gene in a single behavior. It does not mean the gene encodes the behavior; nor does it mean that each complex behavior correlates on a one-to-one basis with genes. Many gene products can be involved in the same process, and there is some redundancy in gene pathways that are used for multiple processes.)

The second study highlights the complexity of the relationships between genes, behavior and the environment. In this case, the authors demonstrated a beautiful example of a different kind of relationship: maternal behavior influencing the genomes of the pups being reared. The story doesn't end there, because the effects on the pups' genomes influence their owners’ behaviors.

Sometimes I imagine that I am someone else's lab rat. (I don't believe in aliens or in God, but I just like to think about this when I experiment with my own laboratory rodents.) I imagine that someone is trying to explain my behavior in terms of specific genes.

The problem with Suzanne [the researchers would report] is that her Xzyl gene is mutated such that she engages in self-destructive behavior. In an experiment consisting of ten trials, when faced with the choice of saving her pride or humiliating herself further, she consistently chose the self-humiliation route. Apparently she believes in this silly thing called 'openness' and 'honesty,' what members of her species often call 'wearing one's heart on one's sleeve.' This behavior results in much emotional pain, yet she consistently chooses the harmful option, also demonstrating an inability to learn.

To investigate further her cognitive defects, we also tested her ability to plan and execute simple tasks involving deadlines. Our subject appears to hate herself. In nine out of ten trials, she left things to the last minute, causing herself a very stressful pre-deadline period. We also tested her motor ability and found an increased tendency to bump into inanimate objects and bruise herself on these occasions.

Finally, we examined our subject's sleep patterns, and have concluded that she has none. We suggest that her emotional ineptitude and cognitive defects may be a symptom of the same deficiency that leads to her sleep problems. The Xzyl gene, first cloned in fruit flies, encodes a calcium-channel protein involved in the neuronal circuitry implicated in what humans call 'common sense.' Mutant alleles of xzyl in humans are associated with self-destructive behavior. Cruelly, the neuronal circuitry involved in awareness of the consequences of such behavior are intact. Further studies are needed to determine how the two neural systems (awareness and self-destructive behavior) interact, and what, if any, therapies may be available to encourage better communication between the two. This work is supported by the International Emotional Sadists Association.

You laugh, but I bet such a study has already been funded.

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A version of this piece originally appeared on the author's blog, which you are encouraged to visit.