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| Heidelberg, 25 August 2006 |
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| A wandering eye
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| The development of the eyes in Medaka fish over time seen through a confocal microscope. Eye cells are labelled in green, brain cells in red. |
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| The researchers: Jochen Wittbrodt, Martina Rembold and Felix Loosli [from
left to right] |
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Single cells come running to form an eye
Press
Release 25 August 2006 [PDF]
Deutsch
Movies:
Cell tracking [.mov, 13 MB]
Eye development [.mov, 6 MB]
Eyes are among the earliest recognisable
structures in an embryo; they start off as bulges on the
sides of tube-shaped tissue that will eventually become the brain.
Researchers from the European Molecular Biology Laboratory
[EMBL] in Heidelberg have now discovered that cells are programmed
to make eyes early in development and individually
migrate to the right place to do so. The study, published in this
week's issue of the journal Science, overturns the textbook model
of the process and suggests that also other organs might be
formed by the movement of single cells rather than sheets of
entire tissues.
Jochen Wittbrodt and his lab at EMBL made the discovery using
advanced microscope techniques to track individual cells in the
transparent embryos of a small fish called Medaka.
"You can think of the tube as a deflated balloon shaped like a
Mickey Mouse," Wittbrodt says. "As the fish grows, the eyes gradually
bulge out from the tube, the way Mickey Mouse ears expand
as a balloon is filled with air. Most scientists have thought that
cells in the neighbouring regions grow to make the bulges. What
we've seen is that individual cells migrate to this area from the
central region of the tube – as if to make ears, tiny rubber particles
had to fly out from the air inside the balloon."
In 2001, Felix Loosli from Wittbrodt's laboratory discovered a
protein called Rx3 that is required for eye formation. Only cells
that will become the eye begin producing this molecule early on
in development. Martina Rembold, also from Wittbrodt's group,
labeled these cells with a fluorescent marker and tracked them
using advanced software developed by Richard Adams at the
University of Cambridge. Following the cells required recognizing
them under the microscope and assembling tens of thousands
of images into 3D movies.
"Rx3 plays a crucial role in giving the cells their identity and
telling them where to go," says Rembold. "Normally, single cells
migrate actively and one-by-one from the centre of the brain to
form eyes. But in strains of fish that have no Rx3, no eyes develop
and the cells remain inside the brain, because nothing tells
them to migrate to the right place."
In the embryo the paths for cell movements are signposted by
cues that by attracting or repelling different types of cells guide
them into the right direction. Thanks to Rx3 eye cells prefer the
cues guiding the way to the eye field. Following them the cells
migrate individually against the stream of brain cells that are
repelled by the same signal. Without Rx3 eye cells lose their preference
and follow the bulk of brain cells into the other direction.
Many other organs are thought to form when sheets of nearby
cells expand to form new shapes. The current study suggests that
individual cell migration might be a more common phenomenon
than scientists have suspected.
"We know that cell migration is important in the formation of
many other organs, such as the heart," Wittbrodt says. "We'd like
to understand how tissues originate and how cells move in the
early embryo and to decipher the cues that tell them where to go.
This approach of tracking individual cells will help us to understand
these processes better."
Source Article
M. Rembold, F. Loosli, R.J. Adams & J. Wittbrodt. Individual cell migration as the driving force for optic vesicle evagination, Science,
25 August 2006
Press Contact
Anna-Lynn Wegener
Press Officer
EMBL Heidelberg
Tel: +49 +6221 387-8452
Email: wegener@embl.de |
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