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Starfish help solve evolutionary puzzle

Starfish help solve evolutionary puzzle

Biologists from Queen Mary University of London (QMUL) have discovered that the history of a hormone responsible for sexual maturity in humans can be traced to genes of starfish.

Puberty and sexual development in humans is triggered by the release of the brain hormone gonadotropin-releasing hormone or GnRH. It was already known that fruit flies (Drosophila) have two GnRH-like hormones – one that mobilises stored fats to power flight (adipokinetic hormone or AKH) and another that makes insect hearts beat faster (corazonin).

What was missing was information from other invertebrate animals that are more closely related to humans than insects. Scientists at QMUL’s School of Biological and Chemical Sciences, working in collaboration with the University of Warwick and KU Leuven in Belgium, discovered that starfish have two GnRH-like hormones, just like in fruit flies.

Professor Maurice Elphick, who led the research team, said: “About half a billion years ago there were animals swimming in the oceans that would have had just one gene that coded for a GnRH-type hormone.

“But then this gene duplicated and the two copies ultimately gave rise to the two GnRH-like hormones that we find in fruit flies and starfish. But somewhere along the evolutionary lineage that gave rise to humans, the corazonin-type hormone was lost.”

What is not clear yet is how it is that the ancestors of humans were able to get by with just one GnRH-type hormone. First author and PhD student Shi Tian, said: “We are investigating where the genes encoding the two GnRH-like hormones are expressed in the strange five-sided bodies of starfish. With this information it may then be possible to find out what these hormones do in starfish.”

The work was supported by the Chinese Scholarship Council and grants from the Biotechnology and Biological Sciences Research Council and the Leverhulme Trust.

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