IGFBP evolution: An interesting case of gene family expansion and retention

Or: How I really should have come up with a better title.

A small announcement: I have an article out as a first author in this month's issue of the journal Endocrinology. It's a nice journal and we spent a long time working on the manuscript so I'm very pleased that it's out. Here's a Worlde word cloud of the whole article... pretty interesting. It sums everything up pretty well actually. It's all about the evolution of the Insulin-like Growth Factor Binding Protein family of genes, or IGFBPs.


Click to see larger.

Why is it worth studying the evolutionary history of this particular gene family you might ask? It's not very well known, generally, and I bet very few know about its functions or that some members seem to be involved in certain types of cancer, for instance. Many times these gene families disappear behind esoteric acronyms and convoluted webs of functional interactions that only the initiated understand, and it's difficult to generate some sort of general interest in them. It all becomes a bit dry. But when you look a bit closer, many "obscure" (at least to the general audience) genes and proteins have a really interesting evolutionary story to tell, something that goes beyond the mere evolution of their gene sequences.

Turn off the lights and let melatonin run free

>> I started the following post about melatonin sometime in March to coincide with my lecture on biological rhythms on our undergrad neurobiology course. But I got really busy and then really sick so I never actually finished it. Here it is then at last.


An all too common sight, at least at my place. This is my Mac glaring. But how is our exposure to low-intensity artificial light before bedtime affecting our sleep cycle?

Twice every year I lecture to undergraduate students in biology and biomedicine about biological rhythms, specifically about circadian rhythms - how the brain regulates your daily cycle of sleep and wakefulness. In this process the small suprachiasmatic nuclei (SCN henceforth) in your hypothalamus and the hormone melatonin, secreted from your pineal gland, play very important roles. The SCN is the "internal clock" of your brain and receives light input from the eyes in order to "reset the clock" every morning, signaling that a new day has started. So daylight itself serves as a signal for the brain that it's daytime and we need to be awake and alert, as far as possible.

One of the things I tell my students that usually raises some eyebrows is that even quite low-intensity light, comparable to the illuminance from a computer or television screen, as seen above, can affect the brain and shift the circadian rhythm significantly. This knowledge goes back to experiments carried out in the mid 90's and raises questions as to how artificial light, such an obvious and constant component of our environment, is affecting our day-night cycle.

In a recently published article in the Journal of Clinical Endocrinology (reference 1 below) a team of researchers has shown indirectly that it's the interplay between the SCN and melatonin secretion, so essential to the regulation of nighttime behaviors, that is affected by the artificial light in our environment.

Oxytocin, ethnocentrism and evolution (pt. 2)

>> Go here for part 1.

I didn't want to risk making my previous post too long, and I wanted to keep it focused on "hormonal determinism", so I set aside a whole branch of my commentary on the link between the hormone oxytocin and ethnocentrism for another post. The findings I comment on were presented by De Dreu and co-workers in the latest edition of PNAS (see reference below).

So, today I want to talk briefly about bad evolutionary arguments.

Oxytocin, ethnocentrism and "hormonal determinism"

>> Go here for part 2.

There is an inordinate readiness, both within scientific circles and in popular scientific understanding, to ascribe direct causation to the actions of hormones, especially when it comes to moods and behaviors. For example, consider how you’d usually interpret the common expression “being hormonal”. I consider the thought that hormones somehow “control” our moods and behaviors a falsehood; a popular misunderstanding or oversimplification that hinders the understanding of what’s actually going on. There is just as little motivation to call a hormone the “love hormone”, the “stress hormone” or the “sleep hormone” as there is calling a gene the “gay gene” or the “god gene” et c. The idea that in fact there is no one gene for property X, Y or Z has become pretty pervasive now, and I think it’s time the same thing happened for the actions of hormones.

Within this context, I want to use as an example a newly published study in PNAS that links the actions of the neurotransmitter and hormone oxytocin to ethnocentrism – the tendency to view one’s own group, the in-group, as more important or superior to other groups.


Molecular structure of human placental mammal, some marsupial, platypus, ratfish and elephant shark oxytocin.

Perhaps more than any other hormone, oxytocin has become the perfect example of the kind of “hormonal determinism” that I mention above: no doubt because the study of oxytocin is a very active field and because it’s been linked to some very fascinating behaviors.

Is there anything fish don't do!? Mucus-feeding and prolactin

Much of my work involves studying fish genomes. Over time I've gotten to know them pretty well and I can only conclude that fish are incredible and inordinately interesting creatures. Unfortunately fish have an undeservedly low standing in the eyes of the general public, as well as many researchers in more mammal-oriented fields, often being referred to as "lower vertebrates" in the great evolutionary story that led to "higher vertebrates" like mammals. In fact, more than half of all vertebrate species are fish, not "higher vertebrates", and fish encompass the great majority of all vertebrate diversity. In most senses fish are the "typical" vertebrates. Their origin set the whole stage for vertebrate development, anatomy and physiology and the fair view of vertebrate evolution should be that reptiles, birds and mammals, basically everything that lives on land, are a subgroup of highly specialized fish, an interesting "side-step" rather than the "crown" of evolution.

So why this preface in defense of fish? I have found a little story that more than anything I've read lately highlights the deep connection between fish and mammals and does a very good job at blurring the distinction between what's considered typically mammal and what fish are capable of. Plus, it relates to my own research.



Discus fish (Symphysodon aequifasciatus). Ref: Flickr.

Behold the discus fish.