Neurobiologists at University of California at San Diego have discovered new ways by which nerves are guided to grow in highly directed ways to wire the brain during embryonic development.
UC San Diego biologists discovered how growth cones at the tips of growing nerves are guided to wire the developing brain. Credit: Yimin Zou,
Their finding, detailed in a paper in the February 15 issue of the journal Developmental Cell, provides a critical piece of understanding to the longstanding puzzle of how the human brain wires itself into the complex networks that underlie our behavior.
The discovery concerns the movements of a highly sensitive and motile structure at the tips of growing nerves called a growth cone. For more than a century, biologists have known that growth cones find their targets by detecting chemical cues in the developing nervous system.
They do that by responding to gradients of chemical concentration and steering nerve cells either up or down the gradient to eventually find the right targets to make the proper nerve connections that then establish neuronal networks.
While many of these chemical guidance cues have been identified over the past decade, scientists still don't fully understand how the growth cone picks up small concentration differences in the developing embryo or how guidance cues enter the growth cone to regulate the cellular machinery to turn growth cones in one direction or another.
Yimin Zou, an associate professor of neurobiology at UC San Diego, and his colleagues had previously shown that a family of proteins known as ''Wnt morphogens'' provide the directional cues for the wiring of circuits in many parts of the developing brain.
''These morphogens are often strategically placed in important organizing centers of the developing nervous system and play a major role in sculpting brain connections,'' said Zou.
In their latest paper, Zou and his UCSD colleagues, Beth Shafer, Keisuke Onishi, Charles Lo and Gulsen Colakoglu, report their discovery that Wnt proteins steer the growth cone by stimulating planar cell polarity signaling.
''Planar cell polarity or PCP refers to the polarized structures and functions of a sheet of epithelial cells along the plane of the tissue,'' he said. ''The direction of our skin hair in our backs, for example, is polarized to point down from our head and a highly conserved genetic program, the PCP signaling system, ensures this type of tissue organization in our skin as well as many other parts of our body.''
The UCSD research team found that the growth cone is equipped with all the PCP components necessary to steer extensions of nerve cells, or axons, to their proper targets within the Wnt gradients.
''This study reveals a novel type of environmental signal which the growth cone responds Planets form in disks of dust and gas that surround young stars. A look at the birth places means a journey into the past of the earth and its siblings.
Now, astronomers have been able to obtain detailed images of the protoplanetary disks of two stars using the Subaru telescope in Hawaii.
This is the first time that disk structures comparable in size to our own solar system have been resolved this clearly, revealing features such as rings and gaps that are associated with the formation of giant planets.
The observations are part of a systematic survey to search for planets and disks around young stars using a state-of-the-art high-contrast camera designed specifically for this purpose.
UC San Diego biologists discovered how growth cones at the tips of growing nerves are guided to wire the developing brain. Credit: Yimin Zou,
Their finding, detailed in a paper in the February 15 issue of the journal Developmental Cell, provides a critical piece of understanding to the longstanding puzzle of how the human brain wires itself into the complex networks that underlie our behavior.
The discovery concerns the movements of a highly sensitive and motile structure at the tips of growing nerves called a growth cone. For more than a century, biologists have known that growth cones find their targets by detecting chemical cues in the developing nervous system.
They do that by responding to gradients of chemical concentration and steering nerve cells either up or down the gradient to eventually find the right targets to make the proper nerve connections that then establish neuronal networks.
While many of these chemical guidance cues have been identified over the past decade, scientists still don't fully understand how the growth cone picks up small concentration differences in the developing embryo or how guidance cues enter the growth cone to regulate the cellular machinery to turn growth cones in one direction or another.
Yimin Zou, an associate professor of neurobiology at UC San Diego, and his colleagues had previously shown that a family of proteins known as ''Wnt morphogens'' provide the directional cues for the wiring of circuits in many parts of the developing brain.
''These morphogens are often strategically placed in important organizing centers of the developing nervous system and play a major role in sculpting brain connections,'' said Zou.
In their latest paper, Zou and his UCSD colleagues, Beth Shafer, Keisuke Onishi, Charles Lo and Gulsen Colakoglu, report their discovery that Wnt proteins steer the growth cone by stimulating planar cell polarity signaling.
''Planar cell polarity or PCP refers to the polarized structures and functions of a sheet of epithelial cells along the plane of the tissue,'' he said. ''The direction of our skin hair in our backs, for example, is polarized to point down from our head and a highly conserved genetic program, the PCP signaling system, ensures this type of tissue organization in our skin as well as many other parts of our body.''
The UCSD research team found that the growth cone is equipped with all the PCP components necessary to steer extensions of nerve cells, or axons, to their proper targets within the Wnt gradients.
''This study reveals a novel type of environmental signal which the growth cone responds Planets form in disks of dust and gas that surround young stars. A look at the birth places means a journey into the past of the earth and its siblings.
Now, astronomers have been able to obtain detailed images of the protoplanetary disks of two stars using the Subaru telescope in Hawaii.
This is the first time that disk structures comparable in size to our own solar system have been resolved this clearly, revealing features such as rings and gaps that are associated with the formation of giant planets.
The observations are part of a systematic survey to search for planets and disks around young stars using a state-of-the-art high-contrast camera designed specifically for this purpose.
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