June 30, 2011 | David F. Coppedge

Cells Have Dimmer Switches

A metaphor has been emerging among biophysicists: cells have rheostats or dimmer switches.  The metaphor implies that some cellular regulatory processes are not just on or off; they have continuous ranges of values that can be finely tuned for the need of the organism.  It's been years since our first report that gene expression is controlled by molecular rheostats (01/10/2003), but this week, the metaphor appeared twice: once for embryonic spinal development in tadpoles, and another for DNA repair response that is “a matter of life or death.”

In PNAS, the metaphor was right in the title: “Development of a spinal locomotor rheostat.”1  Scottish scientists studied Xenopus tadpole spinal cord development.  They found that the first pools of neurons are undifferentiated, but rapidly sort out into ventral and dorsal domains within a day.  As the tadpole encounters more and more need to swim with finesse, the neurons become more specialized.  “This unfolding developmental plan, which occurs in the absence of movement, probably equips the organism with the neuronal substrate to bend, pitch, roll, and accelerate during swimming in ways that will be important for survival during the period of free-swimming larval life that ensues.”  In other words, the developmental program has a kind of foresight into what the tadpole will need, and fine-tunes the “rheostat” of neural specialization to permit the tadpole to interact with its environment.

You have a rheostat in your own cells that is important for survival, too.  Medical Xpress headlined an entry, “The genome guardian's dimmer switch: Regulating p53 is a matter of life or death.”  The p53 protein is well known tumor suppressor.  It plays the role of a critical decision maker for situations where DNA has been damaged.  Should repairs proceed, or should the cell command the affected cell to commit suicide?  Findings at the Salk Institute “shows that a short segment on p53 is needed to fine-tune the protein’s activity in blood-forming stem cells and their progeny after they incur DNA damage.”  Geoffrey Wall at Salk commented,  “It's like a dimmer switch, or rheostat, that helps control the level of p53 activity in a critical stem cell population and the offspring they generate.”

That short segment is “an evolutionarily conserved regulatory segment of p53,” the article observed, but made this curious evolutionary claim: “One problem with p53 is that it apparently evolved to protect the integrity of the genome for future generations, rather than to prolong the lives of individual cells or animals.”  In the unguided, purposeless process of neo-Darwinian evolution, nothing evolves “to” do anything; that would imply teleology.  Salk’s claim that “p53 sometimes goes too far in killing cells or suppressing growth” is countered by what the team is trying to learn: “Scientists therefore are eager to find out how cells naturally regulate p53, so that they can target these mechanisms with drugs.”  Most of the time p53 does a pretty good job.  The authors’ claim about what it evolved to do appears to be an unwarranted anthropomorphism.

1. Zhang, Issberner and Sullar, “Development of a spinal locomotor rheostat,” PNAS June 27, 2011, published online before print June 27, 2011, doi: 10.1073/pnas.1018512108.

The evolutionary storytelling added nothing to scientific understanding.  The existence of molecular rheostats and dimmer switches that fine-tine processes says nothing about how they came into existence and became fine-tuned.  The only rheostats and dimmer switches we know about were intelligently designed.  Even a broken rheostat does not supply evidence for evolution.

Evolutionists preach to each other that they need to quit using teleonomic language, but like other sinners, they never seem to learn.  Press agents and reporters are willing accomplices.  If they were consistent evolutionists, all they could say is, “Stuff Happens.”

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