Behavior genes

Earlier this month, Hopi Hoekstra gave a seminar on the genetics of behavior, a field she is expanding with her research on burrowing patterns in deer mice. In her talk, Hoekstra suggested that behaviors are heritable and, in the case of burrowing patterns, dependent on only a few key genes. Her research is considered revolutionary by many as it may help illuminate mysteries surrounding the origin of behaviors, and even personalities. The idea that certain behaviors could be linked to a few key genes has got me thinking about what these genes are and whether the inheritance of behavior is all that different from the inheritance of any trait. Are the genes actually coding for “behavior” or is the behavior an artifact of an inherited morphology or other trait?

Hoekstra suggested genes for dopamine receptors as being potential candidate genes that affect the burrowing behaviors she observed. But could there be morphological differences such as leg length, or musculature which also may contribute to a mouse’s burrowing ability? Could those few genes that appear highly correlated with burrow length actually be coding for physical traits which would then give rise to behavioral “artifacts?” This leads to the question of what is behavior and whether it is distinct from the physical traits we possess. I hesitate to agree with the idea that there are “behavior genes.” Rather, I wonder if we are confusing certain traits that are heritable with the behaviors that they may give rise to.

In 1958, Erwin Schrodinger wrote a book called Mind and Matter, which discusses the role that human consciousness plays in evolution (I put it on the list of “life-changing” reads). One topic he addresses, of particular interest in light of listening to Hoekstra’s talk, is the “genetic fixation of habits and skills.” Schrodinger’s perspective from half-a-century ago is not all that different from what we are potentially finding today in the field of behavioral genetics: behavior is heritable.  But Schrodinger says something more: behavior and physique cannot be separated. “You simply cannot possess clever hands without using them for obtaining your aims … You cannot have efficient wings without attempting to fly. You cannot have a modulated organ of speech without trying to imitate the noises you hear around you. To distinguish between the possession of an organ and the urge to use it …. would be an artificial distinction,” (p.121). Is behavioral genetics making a field out of this “artificial distinction?” In our own lives we could think of the behaviors we have and ask whether these behaviors are more likely to be a consequence of “behavior genes” or genes for traits that make us more likely to have certain behaviors. I enjoy running. Did I inherit a “running enjoyment” gene or is it more likely that I inherited genes for a certain leg-type? or certain endorphin-craving brain receptors?

Because most things make more sense with analogies (at least to me), I like to think of it this way: Let’s say we have a ball of play-do. It is spherical, smooth and malleable as a consequence of its structural makeup. We place the ball of play-do on an incline slope and it rolls. Is the rolling behavior independent of being round? Would we still see rolling behavior in a flat or frictious environment? Probably not. In my opinion, the quest for “behavior genes” is not different than the same quest we’ve been on for the last century: understanding the distinction and interplay between all genes, their expression and the influence of environment.

 

New serotype of dengue

Dengue fever is caused by a virus primarily transmitted by the mosquito Aedes aegypti. The disease is not associated with a particularly high amount of mortality, but its symptoms are particularly unpleasant. The common name of the disease is “break bone fever” and it gets this moniker from the severe joint pain that often accompanies infection.  There is currently no vaccine for dengue and there is no specific treatment option.  If you contract dengue, you are given supportive care (fluids, ect.).

Envelope protien of dengue virus (Purdue University computer illustration)

Up until recently it was thought there were four distinct serotypes (differentiated by host response to challenge) of dengue circulating. Last week researchers announced that
for the first time in 50 years a new serotype of dengue has been detected.

This is bad news.  It makes vaccine development even more complex.  Any new vaccine will have to protect against 5 serotypes simultaneously.  If it does not there is a risk for cross reactivity in vaccinated patients when they encounter new serotypes. This cross reactivity is thought to be a contributing factor to the emergence of dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS), more severe forms of the disease that include internal bleeding. It also introduces additional complexity into an already complex public health problem.

However, it also represents an amazing opportunity.  The new serotype has only recently emerged and for the first time researchers might be also to trace back this emergence to determine what factors contribute to the making of a new serotype. How did this new serotype interact with mosquito hosts, wild monkey populations, and humans along its way?

Open data (2)

I started a reply to Andrews post on open data which turned more into a blog post in it´s own right. I am a firm believer in open data. That is, after you are done using it. I´ve never been a hoarder, and if I can make someone happy with something I don´t use anymore, great. With data it is even better, as it is more like sharing. It doesn´t mean you will not be able to use it yourself anymore either; I think the chance that someone else will do exactly that with the data as you were planning on doing is rather slim. The chance is greater that someone will do something with it that you either (i) would have never thought of, or (ii) don´t have the right toolset to do so. The net result is likely that you will learn new things.

The downside that I see is that numbers in an excel file alone may be insufficient to fully understand the data. I know this data. They are my babies. I spend numerous hours with these mice and parasites to generate the data. I´ve pipetted more tubes and plates than I can count. I know the peculiarities and sensitivities of the different PCR assays, the history of the parasites, the behavior of the mice and the mornings when Derek was sampling hungover. Moreover, I have thought about this data a lot, under the shower, during a run, in my sleep and during romantic date nights. That is not to say that other people won´t be able to make sense of it. It does mean that I believe I might be able to add useful insight in any observations that anyone has.

So, if anyone ever wants to use my data, please, be my guest! It is satisfying to know that my hard work is still useful for someone else. However, I would be happy, and encourage everyone, to start the dialog too. What is your interest in the data, what are your observations? Let´s have a discussion and together increase our understanding of these infection dynamics, which is, after all, every one´s aim.

Open data

I am a firm believer in open access. It is why I violate all copyright issues and post a pdf of every paper we publish on this site. Damn backward publishers who make that illegal.

But open data…? That makes me a bit tense. It takes years to raise the money, recruit the people, deal with the animal paperwork, the health and safety paperwork, the HR paperwork, the grant administration paperwork….all just to enable folks in the lab to generate novel data. We then have to sweat together during the arduous process of figuring out what to do, and then doing it, and then making sense of the outcomes. Where’s the justice if we just put the raw data out there, for free, for any passing dilettante who can’t be bothered to get their hands dirty…?

It is what it is. For two of Silvie’s papers (2010, 2011), the data are freely available in Dryad (2010, 2011), and we are in the process of posting the raw data for a third (2013). The 2010 data have been available for a few days and have already been downloaded 5 times. The 2011 data came available awhile back; they have been downloaded 51 times.

Fifty one times. Who is that? What are they doing with it? What have they learned? All very intriguing.

Science & science fiction

In the spirit of appreciating good science journalism (and not just complaining about the bad), I found this neat article about science inspired by science fiction. Apparently folks have gotten surprising close to telekinesis via helmet, the repelling gun favored by Batman, and getting photons to interact in ways that might lead to the development of light sabers (practical applications to follow–I can’t imagine people really using it to mow the lawn). All science must be preceded by science fiction, even if people don’t bother to write down their complete chain of what-ifs. My favorite papers are simply well-reasoned sci-fi.

It’s hardest to see the pieces that are missing, and I particularly appreciate papers that examine the life strategies we don’t see. For example, Hurst’s “Why are there only two sexes?” gave us solid expectations about the number of sexes we should expect on this and other life-bearing planets (spoiler alert–it’s two). The downside is that now I can’t help but complain of a lack of realism in any sci-fi that describes aliens requiring more than two sexes to get offspring (lots of Star Trek, Alien Nation, and so on). Now we have a nice mathematical model to show that requiring three or more players is just silly. More relevant to life on this planet is Day, Mideo & Alizon’s “Why is HIV not vector-borne?”–asking what constraints keep HIV from doing everything well. I feel that if I knew just a little more about the evolution of immunity with respect to body size, I could write similar paper about why we don’t see true parasitoids of large animals. There are blowflies, yes, but while they lay eggs in human flesh, they do not burst out of a person’s chest Alien-style. Not to sound ungrateful, but why not?

Blowflies aren't nice, but it could be much, much worse.

Might be a good question to ponder as the space-tourism industry starts to get a foothold…

 

The peacock’s tail

The other day I was watching television and during one of the commercial breaks there was an advertisement for a new cologne, but no attempt was made to explain how it smelled.  So what I’m left wondering is whether I am expected to buy the cologne because I recognize the name or whether I am expected to buy it because a company executive had enough faith in the product to invest advertising dollars into selling it.

I think it’s the latter.  Companies have a limited amount of resources to invest in advertisements for various products, and so they have to prioritize advertising the products that they think can be successful.  Does this make tv ads a form of honest signaling?

Turning the lights on

Penn State is to be congratulated. No, I’m not talking about football (though I hear they’re doing ok), but for the scientific seminar series put on this year. (The organizers of these also deserve major kudos! They have been busy.) Here’s a taste. Speakers this fall have been amazing. I’ve been lucky enough to talk about science with some very accomplished guests, and that’s my favorite part.

credit to http://crimson-shine.deviantart.com/art/Kaleidoscope-148463172

So many talks could cause seminar fatigue, but the recent talks I’ve seen had exactly the opposite effect. Talking science has been like turning on the lights in a dim room, and discovering that the lights are filtered through a spectacular kaleidoscope – in analogy for the way these talks have colored my thinking about research and lit up new areas.

Blinded by vision?

The first step of the scientific method is to ask a question, a step which is prompted by observations. Observations depend on an organism’s limited senses, which in humans disproportionately emphasize detection of visual stimuli. When I think of the questions I ask myself before starting an experiment, they are usually prompted by things I see. A recent article in Nature Neuroscience suggests that when we devote our attention to visual perception, our brains selectively tune out other sensory input (we are not as good at multi-tasking as we think). By favoring visual phenomena, we necessarily start ignoring other senses. If science is prompted by the things we perceive, on a larger scale this has implications for what becomes the focus of our field, and, consequentially, what we may still be missing. What questions would we be asking if we were bats?

In 1989, Marion Isabel Newbigin wrote a short book, Color in Nature (the e-book is free to download) which discusses theories relating evolutionary biology to color and the impact abiotic sources of color (our blue sky, clear water, gray rocks etc.) have on the biological. I got stuck on the following quote: “[Colors] attract [the scientist’s] attention because of their frequently intrinsic beauty and their arrangement into patterns and markings which may exhibit extraordinary constancy,” (Newbigin, p.2). Colors certainly attract our attention but could they also distract our attention?

Newbigin provides three reasons why an understanding of colors in nature may be important: 1. The “conspicuousness of color in natural phenomena,” 2. potential links between color and evolution (as an important phenotypic trait), and 3. use in comparative physiology (e.g. are cantaloupes and pumpkins the same color for the same reason?). I agree that observations of color could spark interesting scientific studies, but it also seems to me that conspicuousness could be dependent on perspective. Colors that seem obvious, and a potentially strong selective trait, to highly vision-centric humans might not be selective for organisms interacting with less visually-minded community members. Do trees see their red fall leaves as conspicuous? WD Hamilton famously hypothesized that red fall leaves serve as a warning signal in defense against insects. But a 2007 review article in PLOS Biology suggests that that idea is dependent on the insects being able to detect color as a warning signal. Are the brilliant reds and yellows perceived by insects as a warning, or are they only wowing us humans? An interesting debate to have while the fall leaves outside MSC are in their explosion of color.

 

Your totally weird animal behavior moment of the week

Watch this (sorry I can’t pause it and talk you through it as Eleanore suggests, but I have great faith that you will pay attention)

The first time I heard about these little guys I was quite amazed, but this is not such an unusual plan. Even within the mosquito family there are a wide range of foraging life styles. Larvae of the Toxorhynchites mosquitoes eat other mosquito larvae so effectively that they are sometimes used in control. They are not a particularly sustainable control option because once they have finished eating other species they will turn on one another.  As a result of this life style they are both gigantic as adults and do not blood feed as adults.  Just to be extra interesting the females of this species never land to lay their eggs.  In fact they do a special “oviposition flight” in which they conduct 6-43 elliptical loops before dropping them off (Collins and Blackwell 2000).

male Toxo

To learn more about this interesting group of mosquitoes go here!

 

 

Ecological videos


“Hi, I’m Troy McClure. You may remember me from such nature films as Earwigs: Eww! and Man vs. Nature: The Road to Victory.”

I’m feeling desperately uninspired to blog this week so I’m going to show you a video instead. Actually, I’m going to show you a lot of videos, assembled in one blog post by Meghan Duffy.

Since it seems relevant, I’m also going to share a teaching tip that was given to me by one of my mentors at Emory. If you’re showing a long video clip in class, break it up by pausing and presenting data from the research being highlighted in the video. This helps reiterate the point(s) of the video, keeps the students from zoning out too much, and gets the students used to looking at – and hopefully interpreting – actual data.

 

When less is more

One of the questions that every theorist stresses over when constructing a model is how complicated the model should be.  The correct answer, of course, is that the model should be exactly as complicated as it needs to be, but no more.

Try this thought experiment.  Look at a glass of water sitting on a nearby table or desk.  Imagine pushing the glass over the edge, and try to follow the trajectory in your head.  My guess is that you can visualize this process fairly well.  You might even be able to picture the shards of glass scattering when it hits the floor, or the shape of the puddle that the liquid ends up making.

We can picture this process so clearly because in our lifetimes we have seen many things fall.  Sometimes the object was a glass of water from a table, sometimes it was a pencil from a desk, sometimes it was an apple from a tree.  And using these observations, we developed a model that allows us to predict how things will fall before they even begin to move.

In the thought experiment above, a glass of water was pushed from a table.  Does the trajectory of the fall change if the water was replaced with beer?  What if the liquid was dyed green?  What if the glass was dyed green?  If the goal is to predict the trajectory of the falling glass, these details don’t matter, and they can be left out of the model.  Interestingly, leaving these details out of the model makes the model more general, and in turn more useful.  I mean, how often do you push a glass of green water off of a table?  What good would that model be?