A team of student researchers from the John Jay College of Criminal Justice have discovered human microRNA genes not shared with any other primate species that may have played an important role in the unique evolution of the human species. The students, under the direction of Professors John Jay, Dr. Hunter R. Johnson and Dr. Nathan H. Lents, discovered at least three families of microRNA genes on chromosome 21.
The team used genome alignment tools to compare the most recent versions of the human and chimpanzee genomes, meticulously searching for new human-specific genetic elements. Starting with the smallest human chromosome, chromosome 21, the researchers were surprised to discover a large region of unique human DNA, called 21p11, which harbors several orphan microRNA genes.
Although the team found that the long arm of human chromosome 21 aligns well with that of other extant ape species, the short arm aligns poorly, suggesting that this region of the human genome has recently diverged considerably. from that of other primates.
According to their analysis of prehistoric human genomes, these changes predate the divergence of Neanderthals and modern humans. The genes also show little or no sequence-based variation within the modern human population. The team therefore hypothesized that the microRNA (miRNA) genes found in this region [miR3648 and miR6724] have probably evolved over time since the separation of chimpanzee and human lineages, over the last seven million years, and are specific to humans.
Using computational tools, the team found with a high degree of probability that the predicted genetic targets of the relevant miRNAs are linked to embryonic development. Both miR3648 and miR6724 have been detected in tissues of the human body, including the brain, and may play a role in the evolution of mankind’s most unique organ. The results point to the intriguing idea that these microRNA genes have contributed to the distinct evolution of our species and the uniqueness of humanity.
“Understanding the genetic basis of human uniqueness is an important undertaking because, despite sharing almost 99% of our DNA sequences with the chimpanzee, we are remarkably different organisms,” said student researcher José Galván. “Small post-transcriptional regulatory elements like miRNAs and siRNAs [small interfering RNA] are underestimated and often misunderstood in the effort 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 their regulation of other genes, meaning that small changes in DNA sequence can lead to far-reaching impacts on the human genome. The creation of miR3648 and miR6724 are prime examples of this process. This study revealed a new possible mechanism for the creation of new miRNA genes by duplication of rRNA genes, which calls for further research on the generality of this phenomenon.
The study’s co-authors include Dr. Nathan H. Lents, professor of biology at the John Jay College of Criminal Justice, Dr. Hunter Johnson, associate professor of mathematics at the John Jay College of Criminal Justice, and a team of students undergraduate researchers: Jessica A. Blandino, Beatriz C. Mercado, José A. Galván, and William J. Higgins.
Source of the story:
Material provided by The City University of New York. Note: Content may be edited for style and length.