THE same pair of proteins choreographs the development of bristles on flies
and hairs in the human inner ear. This finding could eventually lead to
treatments for hearing loss, say biologists.
Fruit flies do not have ears, but detect sound vibrations using stiff
bristles that cover most of their bodies. Two proteins, called notch and jagged,
help arrange the bristles on the developing fly into a fixed pattern. Matthew
Kelley of Georgetown University in Washington DC suspected the same protein duo
might be at work in the cochlea鈥攖he mammalian inner ear鈥攚hich also
has a regular arrangement of sensory hairs. 鈥淭his is one of the few examples of
a precise pattern in mammals,鈥� he says.
Kelley and his colleagues stained cochleae from mice at different stages of
development to reveal which cells had the genes for notch and jagged turned on.
In the early stages, when all cochlea cells were identical, all expressed notch.
Later jagged appeared, but only in cells destined to become hair cells (
Nature Genetics, vol 21, p 289).
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Work on flies had already shown that notch is a cell surface receptor to
which jagged can bind. Kelley believes that hair cells probably secrete jagged
to tell their neighbours to become support cells instead. This keeps the pattern
in the cochlea regular. 鈥淲hen you need to make a precise cellular pattern in any
animal, you鈥檙e going to use this system,鈥� he says.
Most hearing loss is caused by hair cells dying as a result of ageing or
exposure to loud noise. Kelley hopes that understanding how hair cells are born
will lead to treatments for this kind of deafness. 鈥淲e might be able to tweak
the system to regrow the dead hair cells.鈥�