Through millions of years of evolution,
primates have gained the cognitive ability to think that differentiates them
from other mammals. Scientists believe that the gene that accounts for this isosteocrin (OSTN), which is expressed in the neurons of primates as well as in
the bones and muscles of mammals. Scientist Bulent Ataman and colleagues
cultured human neurons in vitro to simulate brain activity and learn more about
the OSTN gene. They then used RNA sequencing to determine upregulated
transcripts, in which they found a few transcripts specific only to human
neurons, the most active one being OSTN. OSTN was also found to be expressed in
the neocortex (which contains cognitive functions) and cortex of primates, and
was expressed in response to brain activity, which makes this gene
activity-dependent.
Ataman and colleagues also discovered the
presence of the myocyte enhancer factor 2 (MEF2) family in primates, which
binds to DNA sequences (MREs) in the neurons, while other mammals lack this
factor. Scientists believe that the creation of MREs are due to a mutation in
nucleotides millions of years ago when primates split off from other mammals.
While other mammals lack the MRE site, primates contain three sites, and when
bound induce transcription in other genes.
Scientists have found that this gene expression
regulates the shape of dendrites, the branches of neurons that send and receive
signals. The scientists conclude that this factor allows the cognitive thinkingin primates as a result of learning, as the expression can change dendrites so
that the movement of signals is much more efficient. This experiment is
important as it explains the reason as to why humans are able to think at a
higher level than other animals, and how we can retain what we have learned to
make predictions and anticipate the future rather than only live in the present.
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