So if you have been in the dark about what’s been making a lot of buzz around the internet today, have no worries. I’m more than happy to explain it to you, because this new research will really help us understand what it means to be human and non-human.
How, you ask?
Well, it identifies a unique protein in human brains and compares that to chimpanzees. This form of comparison is important. Often, I’ve told people that, while it maybe significant that chimpanzees and humans share a remarkable amount of genomic similarity, where we don’t share similarities, areas that span millions of base pairs, the developmental implications are really dramatic.
The research is hardcore molecular biology, specifically proteomics. Proteomics is a branch of molecular biology that seeks to determine the large scale patterns of protein expression and function. The researchers, led by Dr. Bing Su of the Chinese Academy of Sciences in Kunming, China, show,
“a certain form of neuropsin, a protein that plays a role in learning and memory, is expressed only in the central nervous systems of humans and that it originated less than 5 million years ago. The study, which also demonstrated the molecular mechanism that creates this novel protein.”
The publication, ain’t out yet. But I’m getting this all from EurekAlert, a very trustworthy pop-science news outlet run by Science. The divergence time of this protein falls in line with newly assessed dates of human lineage divergence from other great apes. So it has got that going for itself.
The specific paper will be published in Human Variation.
Su had an idea on where to look and what to compare, because her previous work had shown a longer form of the protein, neuropsin II,
“is not expressed in the prefrontal cortex (PFC) of lesser apes and Old World monkeys. In the current study, they tested the expression of type II in the PFC of two great ape species, chimpanzees and orangutans, and found that it was not present. Since these two species diverged most recently from human ancestors (about 5 and 14 million years ago respectively), this finding demonstrates that type II is a human-specific form that originated relatively recently, less than 5 million years ago.
Gene sequencing revealed a mutation specific to humans that triggers a change in the splicing pattern of the neuropsin gene, creating a new splicing site and a longer protein. Introducing this mutation into chimpanzee DNA resulted in the creation of type II neuropsin. “Hence, the human-specific mutation is not only necessary but also sufficient in creating the novel splice form,” the authors state.”
Human version of neuropsin is longer, which alters the efficacy of its function. I don’t know how, but obviously must do something better. Other conclusions have been made, but none are as significant as the ones I’ve bolded in the above quote.
I’ve decided to do some of my own research on neuropsin, to see what we know of it… where it’s located, what sorta promoters it has, etc. So I fired up NCBI’s GenBank and put in ‘neuropsin‘. Sadly, no current genomic information on the gene is up there yet. Some interesting nucleotide and protein sequences are there, as well as a cool 3d model of the protein.
Most importantly, neuropsin has been identified to function as “A Serine Protease Expressed In The Limbic System Of Mouse Brain.” A protease is an enzyme that basically breaks up things, and since serine prefixes it… neruposin functions as a breakdown component of serine, a hydrophilic amino acid that is a constituent of most proteins. Currently three human diseases are attributed to the malfunction of this enzyme, which I wonder what implications that has as far as symptoms? Reduced cognitive functions?
I also wonder why humans have this alternative modified protein in our brains and not chimpanzees, now that I know the function? Does having a second type of neuropsin allow for us to process serine more effectively, ultimately facilitating some of our cognitive differences? I know I already asked that but it is something I don’t fully understand. That’s something the authors advocate to be studied in the future, to identify,
“the biological function of type II neuropsin in humans, as the extra 45 amino acids in this form may cause protein structural and functional changes. They note that in order to understand the genetic basis that underlies the traits that set humans apart from nonhuman primates, recent studies have focused on identifying genes that have been positively selected during human evolution. They conclude, “The present results underscore the potential importance of the creation of novel splicing forms in the central nervous system in the emergence of human cognition.”
Very interesting news, none the less. Definately one of those genes to keep in the back of your head, no pun intended… really. If you like this sorta stuff, please keep in touch with me, and also check out John Hawks who published out an issue of the neuroscience blog carnival, Encephalon. I wish this post coulda made today’s issue, but I just got word of it midday! Maybe next time.
P.S. This article on ‘stalled human evolution‘ maybe also of interest. I haven’t read it yet, but with a headline like that, its bound to have some controversial stuff in it.