Our colleague Rick Sternberg used to say to me, half-jokingly (or, frankly, not really joking at all), “Paul — in animals, every gene ultimately affects everything, one way or another. Pleiotropy as far as the eye can see.”
A new multi-author article, from many leading investigators, open access at Genetics, makes the same point, vividly. From, “Beyond Mendel: a call to revisit the genotype–phenotype map through new experimental paradigms” (emphasis added):
It is thus noteworthy that when one searches for the function of a given gene based on publications on the gene, one will almost always find multiple answers, where researchers have studied the same gene under different experimental conditions, in the context of different cell types or developmental stages or within different regulatory networks. In fact, most genes, in particular those encoding transcription factors and signaling pathways, are active in multiple developmental stages and tissues, allowing them to perform many functions.
Abundant and Telling
This is top-down causation, friends, where the higher-level context determines the function(s) of its lower-level elements. The parallels to natural language are abundant and telling. Take the English word “house,” for instance. The same character string h-o-u-s-e can mean
- a physical residence (a noun)
- to contain something (a verb)
- a particular five card hand in poker (another noun, when preceded by the adjective “full”)
And so on. Function depends on context (the higher level).
Top-down causation makes a lot more sense from a design perspective than from any reductionist, lower-levels-first approach (and the authors of this new article go after the failures of reductionism in their argument, albeit without embracing design). The system tells its parts what to do.
The following, however, sure sounds like design intuitions at work (emphasis added):
…what are the challenges? Consider, for example, from a polygenic perspective, the immensely intricate problem to understanding how the shape and function of the vertebrate skull is generated. A functional skull is the end result of remarkably precise coordination of sensory organ development in which the eyes, ears, and nose are seamlessly incorporated into co-functioning units, and where the feeding apparatus is fine-tuned for optimal processing of the available food, all the while also supporting vocalization.
Those are some sweet design riffs. Where did you get that new guitar? 😉