Student researchers discover genes unique to humans in search for source
of our evolutionary distinctiveness

Date:
March 8, 2022
Source:
The City University of New York
Summary:
A team of student researchers has discovered human microRNA genes
not shared with any other primate species and which may have
played an important role in the unique evolution of the human
species. The students found at least three families of microRNA
genes on chromosome 21.



FULL STORY ==========================================================================
A team of student researchers from John Jay College of Criminal Justice
has discovered human microRNA genes not shared with any other primate
species and which may have played an important role in the unique
evolution of the human species. The students, under the direction of
John Jay Professors Dr. Hunter R.

Johnson and Dr. Nathan H. Lents, found at least three families of microRNA genes on chromosome 21.


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The team utilized genome alignment tools to compare the most recent
drafts of human and chimpanzee genomes, meticulously scanning for novel
genetic elements unique to humans. Beginning with the smallest human chromosome, chromosome 21, the researchers were surprised to find a
large region of human-unique DNA, called 21p11, that 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 aligned
poorly, suggesting that this region of the human genome has recently
and substantially diverged 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 to no sequence-based variation within the modern human population. The team therefore theorized that the microRNA (miRNA)
genes found in that region [miR3648and miR6724] likely evolved in the
time since the chimpanzee and human lineages split, sometime in the last
seven million years, and are specific to humans.

Using computational tools, the team discovered with a high degree
of likelihood that the predicted gene targets of the relevant miRNAs
are related to embryonic development. Both miR3648and miR6724have been
detected in tissues throughout the human body, including the brain, and
may conceivably play a role in the evolution of humankind's most unique
organ. The findings point to the intriguing idea that these microRNA genes contributed to the distinct evolution of our species and the uniqueness
of humankind.

"Understanding the genetic basis for human uniqueness is an important undertaking because, despite sharing nearly 99% of our DNA sequences
with the chimpanzee, we're remarkably different organisms," said student researcher Jose' Galva'n. "Small post-transcriptional regulatory elements
like miRNAs and siRNAs [small interfering RNA] are under-appreciated and
often misunderstood in the effort to understand our genetic differences." Thanks to their small size and structural simplicity, miRNA genes have
fewer barriers to de novocreation than other gene types. MicroRNA genes
can be extremely prolific in their regulation of other genes, meaning
that modest changes to DNA sequence can result in wide-ranging impacts
to the human genome.

The creation of miR3648and miR6724serve as excellent examples of this
process.

This study revealed a new possible mechanism for the creation of new
miRNA genes through duplications of rRNA genes, which calls for further research on how general this phenomenon may be.

The study's co-authors include Dr. Nathan H. Lents, 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 team of undergraduate student researchers: Jessica A. Blandino,
Beatriz C. Mercado, Jose' A. Galva'n, and William J. Higgins.


========================================================================== Story Source: Materials provided by The_City_University_of_New_York. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Hunter R. Johnson, Jessica A. Blandino, Beatriz C. Mercado, Jose' A.

Galva'n, William J. Higgins, Nathan H. Lents. The evolution of de
novo human‐specific microRNA genes on chromosome 21. American
Journal of Biological Anthropology, 2022; DOI: 10.1002/ajpa.24504 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220308155634.htm

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