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Genetic Predictors of Lifespan Studied in Whites and Asians Don’t Apply to Black Youth

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Posted October 1, 2018

Protective caps at the ends of our chromosomes called telomeres protect our cells’ genomic information but shorten each time a cell divides. This shortening of telomeres has been linked to aging and chronic diseases. For example, previous studies have shown that individuals with asthma have shorter telomeres than those without asthma, but it is unclear whether shorter telomeres are a cause or a consequence of the disease.

In the last decade, several studies have tried to overcome this conundrum by identifying genetic predictors of telomere length to allow researchers to separate genetic and environmental drivers of telomere shortening later in life. Based on more than 30 population-based studies of disease risk, telomere researchers have identified a set of these genetic predictors as standard proxies for telomere length.

The ends of chromosomes are protected by specific DNA sequences called telomeres, visualized here in red. Image credit: Thomas Ried, Center for Cancer Research, National Cancer Institute.

However, there are well-known variations in telomere length due to age and racial/ethnic background whose genetic basis is still not well understood. Specifically, telomere shortening is most rapid in early life and throughout adolescence — after that most people’s telomeres shorten at about the same rate. Additionally, African Americans have been shown to have longer telomeres throughout life than European Americans as well as — paradoxically — an accelerated rate of telomere shortening. But despite these important factors, nearly all studies of telomere genetics have been performed in adult populations of European or Asian ancestry, meaning that studies aiming to understand how early environmental exposures impact telomere length across different ethnic groups can’t easily assess the role of natural variations in telomere biology.

To fill this gap in knowledge about genetic markers of telomere shortening in African American youth, the UCSF Asthma Collaboratory, led by principal investigator Esteban Burchard, MD, MPH, of the Department of Bioengineering and Therapeutic Sciences, a joint department of the UCSF Schools of Pharmacy and Medicine, investigated genetic associations with telomere length in 492 healthy individuals under the age of 20 from their ongoing Study of African Americans, Asthma, Genes and Environments (SAGE). Their results were published in Scientific Reports, an open-access online journal published by Nature Publishing Group.

In the new study, researchers led by co-first authors Andy Zeiger, a junior research specialist in the Asthma Collaboratory, and Marquitta White, PhD, an assistant professor, evaluated 40 previously identified genetic predictors of telomere length to see if they accurately predicted telomere length in this study population. They examined 34 commonly cited variants identified in prior studies of Caucasian and Asian adults, as well as six variants identified in a previous European study of Caucasian children, but found that none of these genetic variants were significantly associated with telomere length in African American youth.

The researchers then performed a genome wide association study (GWAS) that identified one novel significant genetic variant associated with telomere length in the young SAGE participants, as well as several variants in genes and pathways highly relevant to telomere biology but which were only loosely associated with telomere length per se in this study group.

“This work represents the first investigation into genetic associations with telomere length in minority youth,” said Zeiger. “We showed that current genetic predictors are not generalizable to our study population of African American youth, a finding that highlights the lack of population diversity in biomedical research. Fully understanding telomere dynamics requires investigations that span different ages and populations.”

The current study only examined snapshots of telomere length in SAGE participants at a single point in time, but the researchers hope that future studies will collect telomere measurements over many years to better understand the dynamic and complex relationships between telomere length and health. Such long-term investigations of telomere length starting at birth could shed light on the clinical implications of this relationship and improve physician-scientists’ ability to predict, prevent, and respond to disease.

Source: UCSF

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