The human brain is one the most complex creations of evolution. Its intrinsically convoluted structure wasn’t always like this though. Or was it? These mini brains in petri dishes could tell us.
Scientists have been trying to understand the brain and its journey for the longest time. Seeking to bridge the gap between how our brain is and how our brain was, this research even addresses the in-betweens. The complex structure of the human brain has always been in the centre stage when it comes to scientific research. Serving as a model for complex but mysterious yet the best machine ever, the brain in its present forms must have evolved from a primitive form where it was not equipped to be this functional.
One way to figure out if the brain has always been what it is right now is to compare it with those of our ancestral cousins. Though fossils are easily found, brains are not. Trying to arrange for the brain of our ancestral cousin- a neanderthal, that died almost 37,000 years ago, has been one monumental task in itself. Yet, to bridge the gap between availability and advancement, a research team grew tiny ‘mini brains’ in Petri dishes. Some of the brains were grown using the gene-editing tool Clustered Regularly Interspaced Short Palindromic Repeats or CRISPR, to have a brain development gene taken from Neanderthal remains.
Researchers started with skin cells of a ‘neurotypical person’- which is a term that is used to refer to individuals who don’t have any known genetic defects linked to neurological disorders– so as to manipulate their genomes to turn them into pluripotent stem cells. Post this, CRISPR comes into play. This is where using CRISPR, NOVA1 gets targeted and swapped in the Neanderthal base pair to replace the modern human one. To ensure precision and avoid any errors that can be caused by DNA changes by CRISPR, resulting cells are sequenced and if any of them have unintended mutations, they are discarded.
Pondering upon questions like what is it in the DNA that differentiates between humans and its probable primitive form? Equipped with similar questions, researchers have now zeroed down to a single gene out for its Neanderthal counterpart in brain tissue grown in a lab dish. When comparing to the brain in it’s present form, the resulting organoid revealed that DNA may have had a major role in the development.
This study is unique not because the topic hasn’t been delved into before, but it’s definitely the first time tiny brains of ancient human cousins have been cultivated so as to compare it with the hybrid of the human organ as it is in its present state.
What Happened In The Experiment?
It is a known fact that the NOVA1 gene plays a vital role in brain development. The researchers replaced the human NOVA1 gene in some of the stem cells that were being used to grow the mini brains, with the help of a NOVA1 gene pieced together from genetic remnants in the bones of long-dead Neanderthals.
A stark difference was observed between the two brains. When observing, the human mini brains tend to appear more like smooth spheres, whereas the neanderthal brains looked more irregular and smaller and took longer to develop comparatively. Even though both the brains were being observed in a petri dish, any outside observer could make out the differences. They were THAT obvious. Yet, closed probing revealed internal differences. It was exhibited that part-Neanderthal mini-brains were more chaotic in their neural activity and produced different sets of proteins than the all-human ones.
The team of researchers had chosen NOVA1 as the specific gene for this experiment solely because of its significant contribution in facilitating the connection between nerves, and because of how fragile it is, in terms of being damaged it can lead to serious neurological disorders and is also related to schizophrenia and autism. These are the primary reasons why it became the focal point of the research concerning brain development. Neanderthal NOVA1 genes are also relatively easy to synthesize. However, just one DNA base pair differs between the Neanderthal gene and the modern human one.
The report further added that the difference in the brain structures gave Neanderthals an upper hand in some case, but robbed them of it at other times. It was noticed that the differences made the Neanderthal brains mature more quickly than their human counterpart, which made them much more capable since a very young age. However, it became the same structural flaw that can be attributed with robbing the Neanderthals of extended development period that most likely gave human children advantages in complex thought and social bonding.