KEY POINTS:
NZ scientists have discovered why our nipples are in the front of the body and shoulder blades in the back.
The unexpected discovery by University of Auckland researchers of the long-sought genetic switch that instructs a developing embryo to form a different front and back has caused a stir in biomedical circles internationally.
The gene, Runx2, has been widely known as the master regulator of bone development, but Dr Maria Flores, senior research fellow of the university's school of medical sciences, has identified it as the central regulator of what develops in the front and at the back of the body.
Dr Flores had been looking at genes that control the development of the gut immune system of zebrafish, which has similar genetic pathways to humans, in a bid to identify genes important in human ailments, such as Crohn's disease.
She identified the genetic switch involved for the front-back axis while studying this specific group of genes, the runx genes.
Her supervisor, molecular medicine specialist Associate Professor Phil Crosier, said it was a role not previously thought to have been associated with this gene.
"When an egg is fertilised and the embryo starts to develop, these axes are genetically determined in the fertilised egg. What happens is that each of these axes tell the embryo what's going to be head and tail, left or right, or front or back.
"It turns out that Runx2 is an absolutely central gene in telling the embryo what's front and what's back."
Axis formation has been much studied, as it governs the biological shape of organisms. "Here supposedly a symmetrically shaped egg gets fertilised, gets turned into this multicellular incredibly complex organism, and so you have to set up these ground rules - in essence, the rules of the game in genetic terms," said Professor Crosier.
Their main interest in the gene was stem cell development, but its role in cancer development is also being researched.
Dr Flores said the three runx genes have all been linked with cancers; the Runx1 in acute myeloid leukaemia, Runx2 in cancer's metastasis or spread and Runx3 in gastric cancer.
Professor Crosier said understanding the genes' role in embryonic development could mean better knowledge of how cancer develops.
"Many of these genes that are important in early embryonic development also turn out to be targets of disease processes like cancer, and that's a recurring theme now in biomedical research."
The results of the Foundation of Research, Science and Technology-funded work are published this week in the advance online publication of Nature Cell Biology.
* RIGHT WAY ROUND
How nature ensures our nipples are in front:
As an embryo develops, genes are switched on to prompt the formation of different axes.
These are essentially the ground rules for the forming of parts of the body - what is left and right, top and bottom, and front and back.
Researchers have identified the Runx2 gene as the long-sought genetic switch that tells the embryo to develop a different front and back, ensuring each part of the body develops as it should.
