Washington
Your brain chemistry existed before animals did
WHEN wondering about the origins of our brain, don't look to Homo sapiens, chimpanzees, fish or even wormsMovie Camera. Many key components first appeared in single-celled organisms, long before animals, brains and even nerve cells existed.
Dirk Fasshauer of the University of Lausanne, Switzerland, and colleagues were studying a pair of essential neural proteins called Munc18/syntaxin1 when they decided to look for them in very simple, single-celled organisms.
Choanoflagellates are aquatic organisms found in oceans and rivers around the globe. Being a single cell, they do not have nerves, yet the team found both proteins in the choanoflagellate Monosiga brevicollis, and the interaction between the two was the same as in neurons (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1106189108). These proteins are found in every nerve cell and control the release of the chemicals which neurons use to talk to each other, called neurotransmitters.
The finding is intriguing on its own, but much more significant when combined with a growing body of evidence that essential brain components evolved in choanoflagellates before multicellular life appeared.
In 2008, Xinjiang Cai of Duke University in Durham, North Carolina, discovered that M. brevicollis has the same calcium channels in its cells as those used by neurons (Molecular Biology and Evolution, DOI: 10.1093/molbev/msn077). Then, in 2010, it emerged that M. brevicollis also has several proteins that neurons use to process signals from their neighbours (BMC Evolutionary Biology, DOI: 10.1186/1471-2148-10-34).
And this year, Harold Zakon of the University of Texas at Austin and colleagues discovered that M. brevicollis has the same sodium channels that neurons use to pass electrical signals along their length (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1106363108).
Put together, these findings suggest that choanoflagellate cells have components for each of the three main functions of neurons: carrying electrical signals along their bodies, signalling to their neighbours with neurotransmitters, and receiving those signals.
Choanoflagellates are our closest single-celled relatives and, because they sometimes come together into colonies, are on the boundary between single-celled and multicellular animals. Some evolutionary biologists believe the first multicellular animal may have been an ancient choanoflagellate colony that stuck together permanently. If that's true, modern choanoflagellates give us a glimpse of how multicellular animals began.
"The choanoflagellates have a lot of precursors for things we thought were only present in animals," says Fasshauer. Today, says Zakon, the nervous system seems "unbelievably complex", but evidence from these tiny organisms suggests it was built up from several simple systems, which evolved separately for different reasons. For instance, Fasshauer suspects M. brevicollis uses Munc18/syntaxin1 to secrete chemicals, much like neurons use it to release neurotransmitters.
Not all of the components required for neurons to work were necessarily present in the ancestors of choanoflagellates, Zakon adds. For example, there is no evidence that they can make neurotransmitters, or that they wire up into networks as neurons do. "The brain is a lot more than a bunch of choanoflagellates," he says.
Read more: http://goo.gl/yzmlJ
WHEN wondering about the origins of our brain, don't look to Homo sapiens, chimpanzees, fish or even wormsMovie Camera. Many key components first appeared in single-celled organisms, long before animals, brains and even nerve cells existed.
Dirk Fasshauer of the University of Lausanne, Switzerland, and colleagues were studying a pair of essential neural proteins called Munc18/syntaxin1 when they decided to look for them in very simple, single-celled organisms.
Choanoflagellates are aquatic organisms found in oceans and rivers around the globe. Being a single cell, they do not have nerves, yet the team found both proteins in the choanoflagellate Monosiga brevicollis, and the interaction between the two was the same as in neurons (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1106189108). These proteins are found in every nerve cell and control the release of the chemicals which neurons use to talk to each other, called neurotransmitters.
The finding is intriguing on its own, but much more significant when combined with a growing body of evidence that essential brain components evolved in choanoflagellates before multicellular life appeared.
In 2008, Xinjiang Cai of Duke University in Durham, North Carolina, discovered that M. brevicollis has the same calcium channels in its cells as those used by neurons (Molecular Biology and Evolution, DOI: 10.1093/molbev/msn077). Then, in 2010, it emerged that M. brevicollis also has several proteins that neurons use to process signals from their neighbours (BMC Evolutionary Biology, DOI: 10.1186/1471-2148-10-34).
And this year, Harold Zakon of the University of Texas at Austin and colleagues discovered that M. brevicollis has the same sodium channels that neurons use to pass electrical signals along their length (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1106363108).
Put together, these findings suggest that choanoflagellate cells have components for each of the three main functions of neurons: carrying electrical signals along their bodies, signalling to their neighbours with neurotransmitters, and receiving those signals.
Choanoflagellates are our closest single-celled relatives and, because they sometimes come together into colonies, are on the boundary between single-celled and multicellular animals. Some evolutionary biologists believe the first multicellular animal may have been an ancient choanoflagellate colony that stuck together permanently. If that's true, modern choanoflagellates give us a glimpse of how multicellular animals began.
"The choanoflagellates have a lot of precursors for things we thought were only present in animals," says Fasshauer. Today, says Zakon, the nervous system seems "unbelievably complex", but evidence from these tiny organisms suggests it was built up from several simple systems, which evolved separately for different reasons. For instance, Fasshauer suspects M. brevicollis uses Munc18/syntaxin1 to secrete chemicals, much like neurons use it to release neurotransmitters.
Not all of the components required for neurons to work were necessarily present in the ancestors of choanoflagellates, Zakon adds. For example, there is no evidence that they can make neurotransmitters, or that they wire up into networks as neurons do. "The brain is a lot more than a bunch of choanoflagellates," he says.
Read more: http://goo.gl/yzmlJ
Global Source and/or and/or more resources and/or read more: http://goo.gl/JujXk ─ Publisher and/or Author and/or Managing Editor:__Andres Agostini ─ @Futuretronium at Twitter! Futuretronium Book at http://goo.gl/JujXk
