FEB 23, 2021 7:34 AM PST

New Insight Into Genetic Basis of IBD From African-American Patients

WRITTEN BY: Carmen Leitch

The small variations in the genome that lead to differences in biology, including risk for diseases, can't be assumed to be the same for different populations, new work has shown. Genome-wide association studies should include people with varied ancestry. For example, the genetic risk factors that affect the development of inflammatory bowel disease (IBD) in African Americans are not the same as those in people of European ancestry.

Image credit: Pixabay

Reporting in the American Journal of Human Genetics, researchers looked at the whole genome sequences from 1,700 Crohn's disease and ulcerative colitis patients and around 1,600 unaffected individuals. The work showed that IBD studies should account for ancestry.

"Even though the disease destination looks the same, the populations look very different, in terms of what specific genes contribute to risk for IBD," said lead study author Subra Kugathasan, M.D., the Marcus professor of pediatrics and human genetics at Emory University School of Medicine among other appointments. "It shows that you can't develop a polygenic risk score based on one population and apply it to another."

Polygenic risk scores are used to describe how likely a person is to develop a complex disease like heart disease based on their genes. As we learn more about the genome, they become more useful.

The biggest risk factor for IBD is having a first-degree relative with a form of IBD, moreso than any environmental factor. This research suggested that for African Americans, the more significant risk locus is PTGER4, a minor one in European populations, noted Kugathasan. But the two primary European gene loci, NOD2 and IL23R, have smaller roles in African Americans. There is overlap in some genetic risk factors, such as IL23R, because there is some European ancestry in the African-American genetic background.

"One of our goals in treating IBD is to move toward a more personalized approach," said Dermot McGovern, M.D., Ph.D., the Joshua L. and Lisa Z. Greer Chair in Inflammatory Bowel Disease Genetics at Cedars-Sinai. "Deciphering the genetic architecture is an important part of this effort. Studies such as this one are vital to ensure that diverse populations, including African-Americans, benefit from the tremendous advances promised by genomic medicine."

Kugathasan noted that there is a therapy being developed for IBD that targets the IL23 receptor pathway, in part because of the risk factor; as such, work on PTGER4 should expand.

This work also revealed some rare genetic variants that are associated with IBD and have not been found in other populations. These variants were linked to a gene involved in nervous system signaling, CALB2.

The researchers were disappointed that they did not discover more variants that can adequately explain IBD risk in African-Americans that is likely to come from the genome, but is not explained by known variants.

Additional research investigating how IBD may be affected by the interaction between genes and environmental factors like diet, toxins, or the microbiome will be needed and may reveal more, suggested Kugathasan.

Sources: AAAS/Eurekalert! via Emory Health Sciences, American Journal of Human Genetics

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
FEB 28, 2021
Microbiology
Tourists Are Often Exposed to Superbacteria
FEB 28, 2021
Tourists Are Often Exposed to Superbacteria
Researchers and clinicians have long been warning about the rise of antibiotic resistant superbugs, pathogenic bacteria ...
MAR 08, 2021
Microbiology
Researchers Discover a New Symbiosis
MAR 08, 2021
Researchers Discover a New Symbiosis
A new type of endosymbiosis has been discovered; the organisms are shown in this image by S. Ahmerkamp, Max Planck Insti ...
MAR 19, 2021
Genetics & Genomics
The Giraffe Genome Explains Some of Its Unusual Characteristics
MAR 19, 2021
The Giraffe Genome Explains Some of Its Unusual Characteristics
Giraffes are unique and have made many evolutionary adaptations. They have a very short sleep cycle, for example.
APR 12, 2021
Cell & Molecular Biology
Deep Subsurface Microbes Are "Living Fossils"
APR 12, 2021
Deep Subsurface Microbes Are "Living Fossils"
Researchers were shocked when they saw the results of a genetic analysis comparing various microbes from around the worl ...
APR 25, 2021
Genetics & Genomics
It's DNA Day!
APR 25, 2021
It's DNA Day!
The genetic instructions that biological organisms use to generate their structures & maintain life are contained in a m ...
MAY 06, 2021
Genetics & Genomics
There's More to Viral DNA Than ATGC
MAY 06, 2021
There's More to Viral DNA Than ATGC
Plants and animals have genomes made of four nucleotide bases, adenine (A), thymine (T), cytosine (C), and guanine (G). ...
Loading Comments...