As promised, today there will be no paper of the day. Instead, I will first write something about the amazing pattern&development workshop, I attended last week. When you read my profile, you know that I work on temperature effect on neural systems. Unfortunately, many people are not aware, that temperature is a strong and general parameter in nearly any biological process. Temperature is defined as the kinetic energy of molecules. So if you heat up your apartment (at the moment it is so freezing cold in Berlin!), you actually make the molecules in the air (oxygen and Co) speed up. The same happens if you heat up a biological cell. All molecules get higher kinetic energy. That results for example in changes of ion channel gating and metabolism rates. So the question is: if everything is changing with temperature, how can it be that "living" works at different temperatures? One organism which experiences quite large temperature changes is the fruit fly (Drosophila). It has a small body size and is cold-blooded. Therefore, it is crucial for the fruit fly to find mechanisms to deal with different temperatures. This temperature adaptation starts already in the development. It is known that environmental temperature during development affects, for example, body size, pigmentation, immunology, behavior, and fecundity of the fly. Nevertheless, I was quite amazed when Christian Schlötterer told us, that when they analyzed gene expression at different temperatures, only 53% of the genes were expressed at all different temperatures, and only 16 of them showed no temperature dependence of their expression level. So the first message of the day: the fruit fly which developed in my cold kitchen, has a different gene expression as the fruit fly in my warm living room. Temperature changes (nearly) everything! But is that true? Maybe gene expression patterns changes and the two flies differ in body size and pigmentation, but you will nevertheless identify both as fruit flies. Both have the same amount of legs for example. That means, that there are steps in development, which are independent of the environmental temperature. One example for that is the body segmentation. Alexander Aulehla gave a great talk about the stability of the body segmentation process with the focus on the development of the somite segments (somite = a division of the embryo in different parts) in mice. Independent of the embryo size and the environmental temperature, there is always the same number of somites, and in the embryo, all somites have a regular shape with a fixed width. How can that happen? Alulehla told us, that this regular segmentation is the result of the oscillatory activity of different signaling pathways in segment precursor cells. All cells in a certain region, produce that oscillatory signal: synchronous with their neighbors but phase shifted. That results in a wave pattern in the segment creation zone. The phase span between "begin and end" of the segment creation zone, is the base for the regular segmentation. Therefore, temperature changes, which affect the wave velocity but not the phase range, has no effect on the size and number of segments. Just the segment creation time changes. So one could say: even if temperature changes everything, for some processes/outcomes it changes nothing at all. Interested, or my description was too confusing? Please read for example:
"Temperature-related reaction norms of gene expression: Regulatory architecture and functional implications." Jun Chen, Viola Nolte, and Christian Schlötterer. Molecular biology and evolution 32.9 (2015): 2393-2402. "Scaling of embryonic patterning based on phase-gradient encoding." Volker M. Lauschke, et al. Nature 493.7430 (2013): 101.
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IdeaI love to increase my general science knowledge by reading papers from different fields of science. Here I share some of them. Archiv
März 2018
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