Friday, October 21, 2011

A gene regulates coordinated embryo development

A single gene seems to play a major role in how our body develops all the different parts during the embryonic stage. While there are a lot of genes responsible for the development of an organism, there is one that rules them all, scientists have shown. Zelda (not the character from the videogame) turns groups of genes on during development, and does that at just the right moment, thereby controlling and coordinating the development of the embryo in time. The discovery adds to earlier findings, that showed that a group of genes called Hox get activated by a precisely timed, but unknown, mechanism to start development of the different body parts. Discovering the function of Zelda is a new step in unravelling the precise mechanisms of one of the most wondrous creations of nature: life.

Zelda's functions were demonstrated in fruit flies. It is not uncommon that these small creatures are choosen for developmental and genetic research: while they do not look like us, they do share genetic and developmental characteristics that are comparable to humans. Because they are easy to breed, and develop rapidly, they are very popular in research.

The function of many genes has been discovered by shutting them off in fruit flies, as has been done with Zelda: when it is absent, the genes required for proper body development are not switched on in time, resulting in a severe malformation in development, and in some cases, the body ceased to develop. This highlights the importance of Zelda in embryonic development. The question remains whether it works the same in humans, something which is harder to unravel, as experimenting on human embryos and inducing malformation is obviously not allowed. However, this gives an important new insight in embryonic development, which expands what we know about one of the most amazing natural phenomena: the development of life from one single fertilized egg cell.

The Zelda gene codes for a transcription factor, that is able to bind to DNA, and consequently switch on a set of genes. It was found that Zelda binds specifically to one piece of code in the DNA, which is found in several places in the genome. Interestingly, Zelda knows which genes should be turned on first, and seems to possess a sense of timing in which the next set has to be turned on.

Earlier, a study was published showing that development of different body parts is controlled by the Hox gene group, where each individual gene is responsible for initiating development of a body part, or segment. The segments were developed in a time-dependent manner, which corresponded to the activation of Hox genes in time. Every 90 minutes, a Hox gene was activated, and every 90 minutes, another body segment was added. This shows that a clock mechanism underlies the initial development of the body. Because Zelda seems to play a role in the coordination of body development, it could be part of the embryonic clock, however no research has been done yet to confirm this.

It is peculiar how fruit fly researchers keep giving weird names to genes that are involved with development. Next to Zelda, there are genes called Sonic Hedgehog, Cleopatra, Dreadlocks and Frizzled, which describe the appearance of the fruit flies after that particular gene is mutated. The researchers that discovered the genes must have had fun while doing it, looking at other peculiar gene names such as 'Scott Of The Antarctic' and 'Glass-Bottom Boat'.

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