The Hedgehog protein plays an important role when proteins talk to one another, especially during the development of the embryo. If this communication is disturbed it can have serious consequences, such as child cancer and deformities. This finding by biologists at Linköping University casts new light on a complicated system.
Hedgehog is a protein that sends signals between cells by bonding to receptor molecules on the cell surface. The system was first discovered among fruit flies. If the protein mutated, the fly larvae would develop hairy backs, resembling hedgehogs.
In mammals and fishes they found a special hedgehog path, a sort of antenna that takes the signal substance into the cell. On the other hand, no such path has been seen among insects.
Such “lower” animals were thought not to need such a sophisticated system – a belief which is now being overturned by a research group at Linköping University. These unexpected results have now been published in the journal Cell Reports.
“We have shown something that people thought did not exist. The cilia on the fruit fly’s smell nerve cells are necessary for the functioning of the signalling,” says Mattias Alenius (pictured), senior lecturer in Developmental Biology.
His research group uses the fruit fly’s (Drosophila) sense of smell as a model system for the study of how nerve cells develop from embryo to complete fly. Now they have shown that the flies have two parallel signal paths and that defects in the Hedgehog system in flies destroy the sense of smell. Among humans, mutations can give rise to rare phenomena such as six-fingered hands, cognitive defects, and common forms of child cancer. The LiU researchers’ fly model may improve opportunities for closer study of cilia signalling in us humans and other vertebrates.
Their discovery also moves the boundaries for the evolution of the Hedgehog system. The signal path via cilia may have developed in primitive organisms far back in time and been preserved and passed down over hundreds of millions of years.
Article: Cilia-mediated Hedgehog signalling in Drosophila by A Kuzhandaivel, S W Schultz, L Alkhori and M Alenius. Cell Reports online, in print 8 May 2014. DOI: http://dx.doi.org/10.1016/j.celrep.2014.03.052
The artist Lennart Samor’s interpretation of the LiU researchers’ discovery is on cover of the current edition of the journal Cell Reports.