The Joy that follows Sex!

By Peter Dearden 31/08/2010 3

Peter K. Dearden. Laboratory for Evolution and Development, Genetics Otago and the National Research Centre for Growth and Development, University of Otago

Do you feel you have never done anything remarkable? Ever feel that you have never achieved the truly stunning? Well stop it! Everyone on earth has survived a process so complex, remarkable and mysterious that they should feel proud. What is it that we have all achieved? It is embryogenesis; the process of cell division, differentiation and growth that made your body from a single fertilized egg.

Embryogenesis is the most complex thing you will ever do, it is the most dangerous thing you will ever do- forget adrenalin sports- embryogenesis is more likely to kill you than anything else. It is a remarkable series of events that scientists have been struggling to understand for thousands of years. Ever since Aristotle described the growth of chicken embryos we have been astounded and intrigued by the process.

Embryogenesis begins with fertilization, with the sperm and egg merging to produce a new organism. Then the new cell begins the ancient chromosome square dance that produces two cells from one, then four from two and on and on. As the cells divide they begin to change, moving from cells that could become anything, to cells that have been sent along a pathway to eventually become liver cells, or brain cells, skin, bone or blood. Embryogenesis is self-organization, with the cells of the embryo programmed by its genes to become particular cell types, at particular times, in particular places. In the past, all we as scientists have been able to do is watch and wonder at this complexity.

But now the focus of research is changing. My PhD supervisor once said to me that scientists of his generation looked at embryos and said ’wow- isn’t that beautiful’, scientists of my generation say ’ wow- how does that work?’. In the past 20 years we have made huge strides in understanding how genes control embryogenesis, and what happens when it all goes wrong.

Why should we care? Well when things go wrong in embryogenesis the effects on a human, or an animal, are often devastating and life-long. One only has to think of the effects triggered by thalidomide to realize the scope of embryogenesis defects. In more severe cases genetic defects causing problems with embryogenesis are often diagnosed as infertility- a condition increasing in western society. It is also important to think of all the factors that might cause effects on embryogenesis- the mother’s nutrition, chemicals in the environment, starting life as an IVF embryo, these common factors may affect embryogenesis, and then later life, in ways we don’t yet understand. For example, children conceived via IVF are, on average, slightly taller than their non-IVF counterparts, who knows why?

For New Zealand, embryogenesis is even more important, with our economy linked heavily to the health of production animals like cows and sheep. Understanding how their health as embryos might affect their future value may be one way to boost our income from the farming sector.

So how do scientists study embryogenesis and the genes that control it? Well, not often in Human embryos, but more often using the embryos of mice, frogs, fish and flies. Indeed the humble fruit-fly has for the past 30 years been the best way to find and study the genes that control embryos. Most remarkably, many of the genes we have found in flies also control and build the embryos of mice and humans.

So, as you contemplate your new found respect for the earliest part of your life, also consider that knowledge that may make New Zealanders both healthier and wealthier is coming from studies of the real heroes of embryology science; flies, frogs and fish!

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