Tuesday, March 29, 2011

Shot of life

I received a shot of life yesterday... well actually I'm living pretty well, it was more my science career that might have been heading for trouble.  Science accepted my paper!  Wohoo!!

Admittedly, I have joked with my colleagues about the science tabloids - Science, Nature and Cell - when another manuscript got flat out rejected.  But when it comes down to it, I read those journals as much and sometimes more than other specialty journals; the quality of the research is generally higher though the interpretations are sometimes more tenacious; and its really good for an early career researcher to have those names on your CV.  So the joking was out of envy.  I'm ecstatic that my paper got in!  Last night we broke open a bottle of wine that we've been saving for a special occasion to celebrate.

... now, waiting on Current Biology to hear about another submission and time to start working on a new manuscript.  It never ends.  Publish or perish - true at any stage of your career.  At least, now I'm enjoying writing and telling stories.

Friday, March 18, 2011

Flies in Heat Part 1: Hot vs Cold

One of the themes of my research interests is understanding how organisms sense and adaptively respond to their environment.  While I am mainly interested in marine larvae, because their responses can have effects on dispersal and thus population connectivity and dynamics, these are not model organisms where the bulk of the progress is occurring.  So it is useful to keep up with some of the fascinating research that is being done on animals like flies, plants (see previous post) and worms (sorry Palin).

Two recent articles uncover some of the secrets of how flies sense temperature.  I'll comment on one article in this post and the second article in Part 2.

Zuker and colleages show that flies have separate neurons in their antennae to sense hot or cold.  The hot neurons and cold neurons project onto distinct but neighboring regions in the fly 'brain' to process this information.  So while hot and cold sensation are related, both use TRP channel receptors and project onto the same part of the brain, they have dedicated machinery (neurons) and processing areas.

While this work on the adult flies is fascinating and provides new mechanistic insight into the neural processing of temperature, it also leaves room for thought on how changes in ambient temperature (e.g. climate change) affect thermosensation.  Before learning anything on the subject, I would have guessed that temperature was sensed as a continuous variable - one set of one neuron type that sensed all temperatures (from hot to cold).  With a division of the work between hot neurons and cold neurons, I can't help but to wonder how the two temperature regimes are divided.  One organism's hot could be another's cold.  Ambient or optimal temperature should lie, I would hope, between the two temperature regimes.

What happens when ambient temperature shifts?  How is ambient temperature sensed? (Part 2 may have some clues to this second question.) Logic would then assume that there are then three types of neurons for temperature sensation - Hot, Cold, and Ambient.  Hot and Cold may be detected like pain stimuli (TRP channels are also involved in pain sensation), whereas Ambient may be more similar to my naive idea of a detecting a continuous gradient.  This would mean that now THREE sensory pathways must be selected upon to adapt to new environmental temperature regimes (climate change).  A tall order indeed.

Gallio, M., T.A. Ofstad, L.J. Macpherson, J.W. Wang, and C.S. Zuker. (2011) The Coding of Temperature in the Drosophila Brain. Cell. 144(4): 614-624.DOI 10.1016/j.cell.2011.01.028

Friday, March 11, 2011

Power of the Ocean

Once again we're reminded of the dangers that lie beneath and the power of the ocean.  Our thoughts and prayers go out to all of our friends, colleagues, and everyone in Japan. 

Wednesday, March 2, 2011

Feeling the Heat - climate change and development

Climate change or no climate change, organisms respond to changes in temperature on a regular basis.  Heat shock proteins are notorious for being up-regulated during periods of temperature shock.  Plants and animals time their reproduction to seasonal variation in temperatures.  We determine our wardrobe choices (at least partially) based on the temperature outside.   Internal clocks are partially set by daily changes in temperature.  But how is temperature sensed?  There isn't a photon or chemical odor to be received. 

Kumar and Wigge have uncovered that chromatin changes mediated by the alternative histone H2A.Z are responsible for sensing temperature in Arabidopsis (a member of the cabbage or mustard family).  Plants without H2A.Z mimic plants grown in warm temperatures - e.g. faster development, fewer leaves and shorter time to flowering.  The idea is that H2A.Z histones are incorporated into the DNA in the promoters of temperature sensitive genes (such as heat shock proteins). The H2A.Z histones change the way the DNA is wrapped to prevent transcription or interfere with repressors.  As the temperature increases, H2A.Z releases the DNA allowing for activator or repressor transcription factors to bind and/or work to rapidly change gene expression. 

With the threat of global warming looming in the not so distant future, understanding the mechanisms by which organisms sense and respond to temperature is increasingly important.  Kumar and Wigge (2010) found that yeast also use H2A.Z to sense temperature.  It will be interesting to see if animals also use H2A.Z in this fashion.  H2A.Z is highly conserved across metazoa, however there could be small changes in the protein that shed light on differential responses to temperature.  When do H2A.Z leave the DNA? 1 degree change, 10 degree change?  Also, perturbation of H2A.Z would reveal the species-specific molecular consequences of increasing temperature.  How does this pathway feed into developmental gene regulatory networks?