Unravelled: brain's memory switch
G.S. MUDUR
An image of one of the mosaic brains of mouse embryos created at the
TIFR, Mumbai
New Delhi, Jan. 20: Indian and US research teams have pinpointed a
gene that creates the cerebral cortex, the part of the brain involved
in higher functions like language, complex thinking and memory.
The scientists at the Tata Institute of Fundamental Research (TIFR),
Mumbai, and the University of California, Irvine, have also provided
the first clues to the genetic machinery that gives rise to the
hippocampus — the brain's memory centre.
In experiments on mouse embryos, the researchers have shown that a
gene named Lhx2 nudges embryonic brain cells to turn into the
cerebral cortex.
"It's humbling to see how the enormous complexity of the cerebral
cortex arises from such a simple step," said Shuba Tole, the head of
the team at the TIFR.
In their experiments, the TIFR researchers created mouse embryos with
mosaic brains — containing some cells with Lhx2 gene turned on and
some cells in which it is off.
They found that embryonic brain cells with Lhx2 turned on transformed
into the cerebral cortex. And the cells with Lhx2 turned off secreted
molecular signals that prompted their neighbouring cells to turn into
the hippocampus, the structure that records all memories — from faces
of friends to ice cream flavours.
Although the TIFR team and the California university researchers
worked independently, they decided to merge their findings and
present them to the world in a joint paper that appeared in the
journal Science on Friday.
In the mosaic brains, islands of hippocampus grew next to the
clusters of cells in which Lhx2 was turned off. While a normal brain
has two hippocampi — one in each half of the brain — some embryos
ended up with five hippocampi.
Tole cautioned that more hippocampi did not necessarily mean greater
memory potential. "The extra hippocampi are probably created at the
expense of cerebral cortex tissue that would have otherwise handled
functions such as perception, decision-making or learning," she said.
In any case, the mosaic brain embryos do not last the full term.
Although the experiments deal with the basic biology of brain
formation, the researchers believe it could have spinoffs in
medicine, specifically in understanding better brain disorders
involving the hippocampus.
"The new understanding of Lhx2's role can potentially be used in stem
cell research to grow new cortical neurons that can replace damaged
ones in the brain," said Ed Monuci, the team leader at Irvine.
Monuci's team showed that Lhx2 activity was critical only during the
stage when the developing cortex is made up of stem cells — neither
before nor after.
http://www.telegrap
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Children's Neurobiological Solutions
http://www.CNSfoundation.org/
Cord Blood Registry
http://www.CordBlood.com/at.cgi?a=150123
The CNS Healing Group
http://groups.yahoo.com/group/CNS_Healing
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