SEP 03, 2019 4:01 PM PDT

Investigating Previously Unmapped Regions of the Human Genome

WRITTEN BY: Carmen Leitch

Reporting in Genome Research, an international team of scientists has used cutting-edge imaging tools to map a region of the human genome that has not yet been described. This region can influence the development of various diseases, and we don’t know much about it yet. This work illustrates that some portions of the human genome have been very difficult to reveal, though it was announced in 2001 that the human genome had been completely sequenced.

Image credit: Max Pixel

"We have realized over time that this is not entirely true, as there are numerous gaps that remain in the reference human genome sequence. These gaps are present in regions that are unmappable and often `invisible' to past and most current sequencing technologies," explained one of the senior study authors Tamim Shaikh, Ph.D., a professor of pediatrics in the section of Genetics and Metabolism at University of Colorado School of Medicine.

In this work, the scientists zeroed in on 22q11, a region of chromosome 22. In this area, there are numerous genetic sequences that are unmappable, called low copy repeats (LCRs). These regions often contain many repetitive sequences and are dynamic; they can cause chromosome rearrangements and deletions and are significant sources of instability. When they lead to large losses or gains in pieces of DNA, they can cause disease. When a section of DNA is lost from 22q11 and 22q11 deletion syndrome arises, it can lead to a variety of symptoms including heart defects, seizures, and mental disorders. The disorder is described in the following video.

With advanced techniques for mapping the genome, fiber FISH and Bionano optical mapping, the research team visualized lengthy DNA molecules. This illustrated the high level of variability between individuals and groups, which was previously unknown. The size differences ranged from hundreds of thousands to more than two million DNA bases. Some individuals had a lot less and some had far more DNA in this area.

"The large differences between people cannot be assessed without the mapping technologies deployed in this study," noted study co-author Dr. Pui-Yan Kwok, Henry Bachrach Distinguished Professor at University of California San Francisco. "Our approach brings clarity to the organization of the highly complex region studied."

"You are mapping these chromosomal fragments back to the genome to see what is different," Shaikh added. "We looked at over 150 apparently healthy people. We found the region in question was drastically different in each person."

"Now we can start asking questions like, `Is someone with more or less DNA more disposed to have a child with disease?'" Shaikh added. "If so, then it might be possible to genetically test parents before they have children."

Shaikh noted that this genomic region is constantly changing. "If you look from one generation to the next you may see changes within the same family," he said. "That is pretty incredible."


Sources: AAAS/Eurekalert! via University of Colorado Anschutz Medical Campus, Genome Research

About the Author
  • Experienced research scientist and technical expert with authorships on over 30 peer-reviewed publications, traveler to over 70 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
JUL 26, 2021
Genetics & Genomics
A Region of Non-Coding DNA That May Help Regulate Telomere Length is ID'ed
JUL 26, 2021
A Region of Non-Coding DNA That May Help Regulate Telomere Length is ID'ed
Many types of cells have to be replenished continuously throughout our lives, and the genome in the nucleus of those cel ...
JUL 28, 2021
Microbiology
Histones May Be Essential to Amoeba-Infecting Viruses
JUL 28, 2021
Histones May Be Essential to Amoeba-Infecting Viruses
Histones are proteins that are used to organize and compact DNA. Some giant viruses called Marseilleviridae have also be ...
AUG 17, 2021
Cell & Molecular Biology
Structural Variations in the Cacao Genome Reflect Local Adaptations
AUG 17, 2021
Structural Variations in the Cacao Genome Reflect Local Adaptations
The genome is more than just its sequence; epigenetic features of DNA, like chemical tags that may be attached, or how i ...
AUG 24, 2021
Genetics & Genomics
A Potential New, Less Costly Treatment for Pompe Disease
AUG 24, 2021
A Potential New, Less Costly Treatment for Pompe Disease
Some rare genetic disorders impair a critical molecule that has to be replaced, or serious disease or disability will oc ...
SEP 20, 2021
Genetics & Genomics
Clinical Trial of CRISPR-Based HIV Treatment Set to Begin
SEP 20, 2021
Clinical Trial of CRISPR-Based HIV Treatment Set to Begin
Human immunodeficiency virus (HIV) is a retrovirus, which is a type of virus that can write its genetic material into th ...
OCT 11, 2021
Microbiology
Small RNAs are Influential in Bacteria, Including Pathogens Like V. Cholerae
OCT 11, 2021
Small RNAs are Influential in Bacteria, Including Pathogens Like V. Cholerae
Like other organisms, bacteria have to take nutrients up from the environment and use them in various metabolic processe ...
Loading Comments...