Retinal cell axons find the right path

 (A. C. Philipsborn)

A team of neuroscientists, led by Friedrich Bonhoeffer of the Max-Planck Institute for Developmental Biology in Tubingen, in collaboration with Swiss nanoscientists, have developed microscopic chips to investigate axon guidance.

A technique called microcontact printing was used to produce a pattern of the Ephrin A5 guidance molecule on the chip. (Ephrin A5 is known to be involved in guiding axons during development of the retinotectal pathway.)

The image above shows a chick retinal neuron growing on the chip. The lines of blue rectangles are EphrinA5 molecules arranged in a concentration gradient. The experiments showed that the total concentration of guidance molecule encountered, together with the steepness of the gradient, provided a stop signal for the growth cone.