Researchers have discovered genes unique to humans in search of the source of our evolutionary difference

(ORDO NEWS) — A group of student researchers at John Jay College of Criminal Justice have discovered human microRNA genes that are not found in any other primate species and may have played an important role in the unique evolution of the human species.

The students, led by John Jay College professors Dr. Hunter R. Johnson and Dr. Nathan H. Lenz, discovered at least three miRNA gene families on chromosome 21.

The team used genome alignment tools to compare the latest draft human and chimpanzee genomes, carefully scanning them for new genetic elements unique to humans.

Starting with the smallest human chromosome, chromosome 21, the researchers were surprised to find a large stretch of DNA unique to humans, called 21p11, that contains several orphan miRNA genes.

While the team found that the long arm of human chromosome 21 matched well with chromosomes of other primate species, the short arm matched poorly, suggesting that this region of the human genome is recent and diverged significantly from other primate genomes.

According to the analysis of the genomes of prehistoric humans, these changes occurred before the divergence of Neanderthals and modern humans. In addition, these genes are practically the same in sequence in the modern human population.

Therefore, the team hypothesized that the microRNA (miRNA) genes found in this region [miR3648 and miR6724] probably evolved in the post-chimpanzee and human lineage split, sometime within the last seven million years, and are specific to humans.

Using computational tools, the team found with high probability that the predicted target genes of the respective siRNAs are associated with embryonic development.

Both miR3648 and miR6724 have been found in tissues throughout the human body, including the brain, and may play a role in the evolution of humanity’s most unique organ. The results of the study suggest intriguingly that these miRNA genes have contributed to the evolution of our species and the uniqueness of humanity.

“Understanding the genetic basis of human uniqueness is important because, despite the fact that we share almost 99% of our DNA sequences with chimpanzees, we are remarkably different organisms,” said research student José Galván.

“Small post-transcriptional regulatory elements such as miRNAs and siRNAs [small interfering RNAs] are underestimated and often misunderstood in an attempt to understand our genetic differences.”

Due to their small size and structural simplicity, miRNA genes have fewer barriers to de novo creation than other types of genes. MicroRNA genes can be extremely prolific in regulating other genes, which means that modest changes in DNA sequence can lead to wide-ranging impacts on the human genome.

The creation of miR3648 and miR6724 is a perfect example of this process. This study has identified a new possible mechanism for the creation of new miRNA genes by duplication of rRNA genes, which warrants further study of how general this phenomenon may be.

The co-authors of the study are Dr. Nathan H. Lenz, Professor of Biology at John Jay College of Criminal Justice, Dr. Hunter Johnson, Associate Professor of Mathematics at John Jay College of Criminal Justice, and a group of research students: Jessica A. Blandino, Beatriz C. Mercado, José A. Galvan and William J. Higgins.

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