Scientists have taken chimpanzee and bonobo skin cells and turned them into pluripotent stem cells (iPSCs), a shape-shifting type of cell that can turn into any type of cell tissue found in the body, to find out what distinguishes humans from apes.
Researchers regularly use iPSCs to "model diseases" when it would be hard to obtain affected tissue from a living person or animal, a Salk Institute for Biological Study news release reported.
The team compared iPSCS from great apes, which are out closest relatives to humans'. The researchers wanted to see what separated humans from the apes.
"Comparing human, chimpanzee and bonobo cells can give us clues to understand biological processes, such as infection, diseases, brain evolution, adaptation or genetic diversity," senior research associate Iñigo Narvaiza, who co-led the study, said.
"Until now, the sources for chimpanzee and bonobo cells were limited to postmortem tissue or blood. Now you could generate neurons, for example, from the three different species and compare them to test hypotheses,"Narvaiza said.
The researchers found "disparities in the regulation of jumping genes or transposons." Transposons are a part of the DNA that can "copy and paste" themselves in different spots in the genome. The jumping genes could allow for rapid DNA shuffling, which could aid in the evolution of our genome.
Two gene codes were found to restrict a jumping gene nicknamed L1. Humans were found to have higher levels of these restrictors called called APOBEC3B and PIWIL2.
"We weren't expecting that," senior staff scientist and study co-leader Carol Marchetto said. "Those genes caught our eyes, so they were the first targets we focused on."
Jumping genes have the ability to "completely disrupt genes," or even process them into entirely new proteins.
The team marked L1 with fluorescence, and observed that there were more fluorescent iPSCs from non-human primates then humans. They also found that when they produced iPSCs with too much APOBEC3B and PIWIL2, it "dampened the mobility and reduced the appearance of newly inserted DNA in the non-human primate cells."
The results suggest L1 insert themselves in human genomes less often than in non-human primates.
"The question that remains is, what would be the impact of differences in L1 regulation? "It could mean that we have gone, as humans, through one or more bottlenecks in evolution, that decrease the variability present in our genome," Marchetto said.
