Daily Archives: February 27, 2015

Human evolution questioned: 'Big brain gene found humans, not chimps'

A single gene may have paved the way for the rise of human intelligence by dramatically increasing the number of brain cells found in a key brain region.

This gene seems to be uniquely human: It is found in modern-day humans, Neanderthals and another branch of extinct humans called Denisovans, but not in chimpanzees.

By allowing the brain region called the neocortex to contain many more neurons, the tiny snippet of DNA may have laid the foundation for the human brain's massive expansion.

"It is so cool that one tiny gene alone may suffice to affect the phenotype of the stem cells, which contributed the most to the expansion of the neocortex," said study lead author Marta Florio, a doctoral candidate in molecular and cellular biology and genetics at the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, Germany.

Still, it's likely this gene is just one of many genetic changes that make human cognition special, Florio said.

An expanding brain

The evolution from primitive apes to humans with complex language and culture has taken millions of years.

Some 3.8 million ago, Australopithecus afarensis, the species typified by the iconic early human ancestor fossil Lucy, had a brain that was less than 30 cubic inches (500 cubic centimeters) in volume, or about a third the size of the modern human brain.

By about 1.8 million years ago, Homo erectus was equipped with a brain that was roughly twice as big as that of Australopithecus.

Read the rest here:
Human evolution questioned: 'Big brain gene found humans, not chimps'

A single gene may have helped pave the way for the rise of human intelligence by dramatically increasing the number of neurons found in a key brain region.

This gene seems to be uniquely human: It is found in modern-day humans, Neanderthals and another branch of extinct humans called Denisovans, but not in chimpanzees.

By allowing the brain region called the neocortex to contain many more neurons, the tiny snippet of DNA may have laid the foundation for the human brain's massive expansion.

This embryonic mouse cerebral cortex was stained to identify cell nuclei (in blue) and a marker for deep-layer neurons (in red). The human-specific gene known as ARHGAP11B was selectively expressed in the right hemisphere: Note the folding of the neocortical surface.

"It is so cool that one tiny gene alone may suffice to affect the phenotype of the stem cells, which contributed the most to the expansion of the neocortex," said study lead author Marta Florio, a doctoral candidate in molecular and cellular biology and genetics at the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, Germany.

She and her colleagues found that the gene, called ARHGAP11B, is turned on and highly activated in the human neural progenitor cells, but isn't present at all in mouse cells. This tiny snippet of DNA, just 804 genetic bases long, was once part of a much longer gene. Somehow, this fragment was duplicated, and the duplicated fragment was inserted into the human genome.

In follow-up experiments, the team inserted and turned on this DNA snippet in the brains of mice. The mice with the gene insertion grew what looked like larger neocortex regions.

The researchers reviewed a wide variety of genomes from modern-day and extinct species confirming that Neanderthals and Denisovans had this gene, while chimpanzees and mice do not. That suggests that the gene emerged soon after humans split off from chimpanzees, and that it helped pave the way for the rapid expansion of the human brain.

Florio stressed that the gene is probably just one of many genetic changes that make human cognition special. [The Top 10 Things That Make Humans Special]

The gene was described in a paper published online Thursday by the journal Science.

Follow this link:
'Big Brain' Gene Found in Humans, But Not in Chimps

A better understanding of genetics role in mental illness will lead to better treatments, according to scientists who participated Thursday in the Massachusetts General Hospital Leadership Council for Psychiatrys ninth annual mental health symposium.

Scientists first identified genetic risk factors related to mental disorders about six years ago, said Dr. Jordan Smoller, director of the psychiatric and neurodevelopmental genetics unit in the hospitals Center for Human Genetics Research. Since then, nearly 200 genetic risk factors have been confirmed, Smoller said.

Genetic markers overlap in five disorders bipolar, schizophrenia, depression, attention deficit hyperactivity disorder and autism, Smoller said.

Were seeing some of these connections and the hope is (that) were going to be able to move towards a diagnostic system that is not simply based upon symptoms but on an understanding of the underlying mechanisms of mental illness, he said.

Another speaker, Dr. Sabine Wilhelm, chief of psychology, discussed body dysmorphic disorder.

About 2 percent of Americans have the condition, Wilhelm said. People with the disorder are preoccupied with a perceived flaw or flaws in their appearance. This intense focus on appearance is linked with an increased risk of depression and/or anxiety. People with the condition are 45 times more likely to commit suicide than the general population, she said.

High doses of serotonin reuptake inhibitors can help alleviate the disorder, though the medication takes at least six weeks to work, Wilheim said. That drug is often used in conjunction with cognitive behavior therapy designed to pull a patients focus away from the perceived flaw and to boost his or her self-esteem, she said.

Parents can help children avoid the disorder by communicating positive comments about their own bodies, Wilhelm said.

Dont make make major comments about wrinkles and scars, things like that, Wilhelm said. She urges parents to be careful how they talk to their kids about their looks.

It is important to compliment girls for their academic and athletic prowess, rather than focus on their physical beauty, she said.

Go here to read the rest:
Symposium: Genetics role in mental illness key to better treatments