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Pregnancy Timeline by SemestersFemale Reproductive SystemFertilizationThe Appearance of SomitesFirst TrimesterSecond TrimesterThird TrimesterFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterDevelopmental Timeline
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May 31, 2012--------News Archive Return to: News Alerts


A few simple changes during the early development of mammals led
to the creation of complex structures such as the human brain.

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Handful of Gene Changes Led to Huge Changes In Human Brain

Changes to just three genetic letters - among billions - led to the evolution and development of our motor sensory network, and laid the groundwork for characteristics of our brain

Yale University researchers report that this network provides the direct synaptic connections between the multi-layered neocortex in the human brain responsible for emotions, perception, and cognition and the neural centers of the brain that make fine motor skills possible.

A description of how a few simple changes during the early development of mammals led to the creation of complex structures such as the human brain was published May 31 in the journal Nature.

"What we found are the genetic zip codes that direct cells to form the motorsensory network of the neocortex," said Nenad Sestan, associate professor of neurobiology, a researcher for the Kavli Institute for Neuroscience, and senior author of the paper

The paper investigated the genetic changes that occur during the early stages of development of an embryo and that direct cells to take on specific functions.


Bits of DNA that do not code for proteins are called the cis-regulatory elements, and have been previously identified as critical drivers of evolution. These elements control the activation of genes that carry out the formation of the basic body plans of all organisms.


Sungbo Shim, the first author, and other members of Sestan's lab identified one such regulatory DNA region, which they named E4, that specifically enhances development of the corticospinal system.

E4 is conserved in all mammals, indicating its importance to survival, the scientists explain. The lab also discovered how SOX4, SOX11, and SOX5 – sections of DNA called transcription factors — control the expression of genes and operate cooperatively to shape this network in the developing embryo. The changes in the genetic alphabet needed to trigger these evolutionary changes were tiny, note the researchers.


By manipulating only three genetic letters, scientists were able to functionally "jumpstart" regulatory activity in a zebrafish.


The authors also show that SOX4 and SOX11 are important for the layering of the neocortex, an essential change that led to increased complexity of the brain organization in mammals, including humans.

"Together, our fine motor skills that allow us to manipulate tools, walk, speak, and write, as well as our cognitive and emotional abilities that allow us to think, love, and plan all derive from these changes," Sestan said.

Sestan's lab is also investigating whether other types of changes in these genes and regulatory elements early in development might lead to intellectual disability and autism.

Other Yale-affliated authors of the paper are Kenneth Y. Kwan and Mingfeng Li.

Primary funding for the research came from the National Institutes of Health.

Original article: http://www.eurekalert.org/pub_releases/2012-05/yu-hog052912.php