字幕表 動画を再生する 英語字幕をプリント Either Douglas Adams was right, and mice are protrusions of hyperintelligent pandimensional beings into our universe, or we are on our way to making Pinky and the Brain a reality... Hey science news fans! I’m Dr. Kiki from This Week in Science here for DNews. Where did people get our big brains? Evolutionary research suggests that something happened in our past triggering a rapid expansion of a part of our brains called the neo-cortex, which is involved in higher level cognitive functions like language and math. It could have been a cultural advancement, like cooking, that freed up more energy for the brain. But, the many underlying genetic factors that differentiate the human brain from our nearest primate cousins are virtually unknown. Studies scanning the human genome for genes that might be the root of our unique brain have found many human-specific genetic sequences that regulate the activity of genes. These sequences are called ‘enhancers’. But, the question remained whether there any enhancers in the human genome that specifically influence the development of the human brain? In a study published on February 19th, 2015 in the journal Current Biology, scientists reported that they had discovered a human gene enhancer called Human-accelerated regulatory enhancer 5, or HARE 5, that does just that. In mice, it led to the development of larger brains. Transgenic mouse embryos were created using either a chimpanzee version of HARE 5 or the human version of the gene enhancer. When the two groups of mice were compared, it was obvious that the human HARE 5 activated earlier in development, and triggered a more robust response than the chimp version. The young neural cells in the brain, called neural progenitor cells, proliferated more quickly under the influence of human HARE 5, which led to bigger brains. Twelve percent bigger than those with chimp HARE 5 to be exact. But, do bigger brains mean that these HARE 5 mice would be smarter than the average mouse? That’s outside the scope of this particular study, but a study published in the Journal of Neuroscience in December, 2014, injected immature human glial cells, the cells that pack in around neurons in the brain, into the brains of baby mice. Not only did these human cells completely usurp the mouse glial populations, but also resulted in four times better performance on a memory test than control mice. It’s thought that the human cells allowed the mouse brains to work more efficiently, but didn’t actually change how they functioned. So, the mice were still mice, just a little smarter thanks to the human glial cells. Yet, this research raises the question of how far we should go when mixing human cells and genes with other animal species. Our ability to learn by studying humans is limited because we can’t very well go around chopping people up in the name of science. Since the advent of stem cell research and genetic manipulation we have gained the ability to mix our cells and genes within other animals, and see how they work. Animals with human-like organs and cells make research that would otherwise be impossible possible. The HARE 5 researchers plan to continue this research, so we will very likely find out whether this gene enhancer results in smarter mice. The point, however, is not to make a better, faster, stronger mouse, or even to make human-like mice. The point of this line of research is to discover more about the human brain, to discover what makes it different, and to learn why some people get neurodegenerative disorders when others don’t, so that we can individualize treatments appropriately. Will research in this vein help humanity, or will it inevitably lead to hyperintelligent mice taking over the Earth? Will we bow down to our mousey overlords?