The Genetic Junk That Makes Us Human

We are 98.8% similar to chimpanzees in our DNA, but we are still a different species. Within that remaining 1.2%, a key DNA sequence once thought of as junk might unlock our human uniqueness.

Using stem cells coaxed into becoming neurons, researchers have identified a gene that distinguishes human nerve cells from chimpanzee nerve cells. They also found that a sequence of DNA once considered “junk” has total control over this human-specific gene.

Only about 2% of our DNA sequences contain the codes for building proteins. Biologists often have focused on these regions in comparing our DNA with that of other species. But the remaining 98% that doesn’t encode protein-making instructions isn’t junk and has important functions.

The researchers found that the noncoding sequence regulates a gene that’s crucial in human brain development. In their findings, published in Cell Stem Cell, this gene was especially active in the front of the developing brain, where humans and chimps differ substantially. The noncoding DNA sequence controls how the gene is used.

This finding adds a step to the sequence of events for making a human brain, giving researchers even more to do in the search to understand how we differ from our closest cousins. Grasping what makes us uniquely human could reveal new insights into conditions that only humans experience, such as schizophrenia.

The study was supported by grants from the Swedish Research Council, the Swedish Brain Foundation, Cancerfonden, Barncancerfonden, the Swedish Society for Medical Research, and the Swedish Government Initiative for Strategic Research Areas (MultiPark & StemTherapy). The authors have disclosed no relevant financial relationships.

Cell Stem Cell. Published online October 7, 2021. Full text

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