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
SEP 14, 2020
Clinical & Molecular DX
Cell Line Authentication Using STR Analysis
SEP 14, 2020
Cell Line Authentication Using STR Analysis
Imagine you’re studying colon cancer using a colon cell line model. After three painstaking years of research, you ...
SEP 16, 2020
Genetics & Genomics
Epigenetic Defects Are More Common in People Than Thought
SEP 16, 2020
Epigenetic Defects Are More Common in People Than Thought
The genome still holds many secrets, some of which probably have a direct relationship to human disease. Beyond genes th ...
OCT 09, 2020
Genetics & Genomics
Using CRISPR to Destroy Cancer Cells
OCT 09, 2020
Using CRISPR to Destroy Cancer Cells
Researchers have developed a way to selectively target certain cancer cells with CRISPR.
NOV 03, 2020
Genetics & Genomics
One Eight Cancer Patients Also Carry Inherited Genetic Mutations
NOV 03, 2020
One Eight Cancer Patients Also Carry Inherited Genetic Mutations
Genetic sequencing technologies have rapidly advanced, reducing the time required to sequence the entire human genome fr ...
NOV 08, 2020
Genetics & Genomics
Drug-Resistant Microbes Persist in Hospitals After Deep Cleaning
NOV 08, 2020
Drug-Resistant Microbes Persist in Hospitals After Deep Cleaning
Researchers have found that drug-resistant bacteria can hang around even after deep cleaning. They used genome sequencin ...
NOV 23, 2020
Genetics & Genomics
Unusual Mutation Acts as a Kind of Gene Therapy
NOV 23, 2020
Unusual Mutation Acts as a Kind of Gene Therapy
Clinicians have identified a patient with a rare inherited disorder that disrupts the production of fresh blood cells, a ...
Loading Comments...