Cytoskeleton Is It in Plant or Animal Cells

How to make animals smarter: Just add human brain cells

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It is easy to dismiss much of the continual outpouring of research that claims to make creatures smarter by changing a few genes around, or even giving them human genes. If you try enough different kinds of tests, you can probably find a few where the altered animals show some arbitrarily significant difference in performance, and then report it as progress. While that is a cynical view, it reflects the realities often observed in our somewhat stagnant system of grant-funded research. Today, a team of neuroscientists claim to have boosted the learning rate and memory of mice by grafting fetal human brain cells onto their brains. This particular hack has cast the net a little further, and gives us a unique insight into how brains work, and how we might soon be able to build superbrains.

When a human brain is compared to a smaller mammalian brain, some features, like the thickness of the cortex, remain relatively constant. Others, like the range and density of connections per cell do not. For example, in evolving larger brains, a neuron that suddenly needs to supply connections to other neurons up to 10cm away typically responds by becoming more massive, and retaining more protein manufacturing compartments.

Scaling in the opposite direction, towards miniaturization, is often not simply evolution in reverse, as it tends to involve optimization of different feature sets altogether. An extreme example of miniaturization can perhaps best be seen in the world's smallest wasp, whose brain is comprised of just 7000 cells. As the startling image to the right shows, the entire creature is actually smaller than the common single-celled paramecium or amoeba. In this wasp, all of the neurons, except around 400 of them, have responded to evolutionary pressures with a previously inconceivable fix: they have disposed of their nuclei altogether.

How do brain cells respond when transplanted across species and scale?

The cells transplanted into the mice were not neurons but astrocyctes, a kind of cell that expresses a set of proteins largely complimentary to those of neurons. The same might be said for its functions. The image at the top of the story shows a fluorescent green human astrocyte which is around twenty times the volume of the (red) mouse astrocytes. The cell has integrated perfectly into its new host and was shown to form stable junctions with both the native mouse cells, and other human-derived cells. The video above shows these astrocytes communicating with waves of calcium ions. A profound feature revealed by this study of astrocytic scaling is that not only do the human cells integrate signals over a larger area, these waves propagate roughly three times as fast.

The cells in this study where carefully isolated from progenitor cells — cells that are still pregnant with the potential to become different kinds of cell. Other researchers, however, have successfully generated these same kinds of cells from mature human skin cells, suggesting a more readily-available source. The main function of these cells is to transduce nutrients from the capillaries to the neurons and swaddle synapses within their range. Transplanting a smattering of astrocytes alone is probably not going to make anyone any smarter, but they are a necessary component to have if new modules of tissue (or hybrid bionic devices) are going to be transplanted wholesale into brains. The value of studies which transplant across species and scale is to be able to more readily observe the behaviors and tendencies that you would not necessarily see right away when transplanting like to like.

One component that the study suggested was critical to the increase in performance of the transplanted rats on behavioral and memory tests, was the secretion of a substance called TNFalpha (Tumor Necrosis Factor). When you pop in cells that are used to supplying these potent elixirs to large brains, you want to find out if the secretion is preprogrammed by the cell genetics, or locally controlled by interactions with its neighbors. As the name suggests, if you are not making an appropriate amount of the stuff, and start to see tumors sprouting up, its may be time to start looking at other options.

Before we would attempt anything remotely similar to these kinds of procedures in humans, there are many safeguards yet to be established. Extending the scope to include other factors and cell types will provide great benefit to the difficult but potentially rewarding science of neural transplantation.

Now read: First map of the human brain reveals a simple, grid-like structure between neurons

Research paper: DOI:10.1016/j.stem.2012.12.015 – "Forebrain Engraftment by Human Glial Progenitor Cells Enhances Synaptic Plasticity and Learning in Adult Mice. Cell Stem Cell"

Cytoskeleton Is It in Plant or Animal Cells

Source: https://www.extremetech.com/extreme/150291-how-to-make-animals-smarter-just-add-human-brain-cells

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