Genes Must Be Expressed in the Right Order
A team of scientists in Switzerland made neural cells switch on a transcription factor earlier during the embryo’s development. The result? Axons (long branches of nerve cells) refused to grow to the spinal cord and to the peripheral target. To the mice, this meant they couldn’t feel things on the skin due to stunted nerves. The paper is published in PLOS Biology. A synopsis of this paper in the same issue (published April 26) explains why the order of expression is important:
Building an embryo is like building a house: everything has to be done at the right time and the right place if the plans are to be translated faithfully. On the building site, if the roofer comes along before the bricklayer has finished, the result may be a bungalow instead of a two-story residence. In the embryo, if the neurons, for example, start to make connections prematurely, the resultant animal may lack feeling in its skin.
On the building site, the project manager passes messages to the subcontractors, and they tell the laborers what to do and where. In the embryo, the expression of specific transcription factors (molecules that tell the cell which DNA sequences to convert into proteins) at different stages of development and in different places controls the orderly construction of the body. (Emphasis added in all quotes.)
1 Hippenmeyer, Arber et al., “A Developmental Switch in the Response of DRG Neurons to ETS Transcription Factor Signaling,”, Public Library of Science Biology Volume 3 | Issue 5 | MAY 2005, DOI: 10.1371/journal.pbio.0030159.
This sounds remarkably like the illustration made in the film Unlocking the Mystery of Life as an argument for intelligent design. It’s not just the molecular machines themselves that are irreducibly complex; the ways they are constructed – the assembly instructions and developmental processes – are themselves irreducibly complex. Like Jonathan Wells quips, “what you have is irreducible complexity all the way down.” Undoubtedly the journal didn’t mean to make a case for intelligent design, but it sure didn’t make a case for naturalism; neither the authors of the paper nor the synopsis mentioned evolution once.