Alzheimer’s researchers examine genes in Puerto Rican and Latino families

MIAMI — With Latinos 1.5 times more likely to develop Alzheimer’s than whites, researchers are uncovering more about how genetics plays a role in their greater risk of developing the disease.

University of Miami researchers teamed up with doctors in Puerto Rico, Peru and Africa to look for new genetic factors that contribute to risk factor and protection against Alzheimer’s in order to find new drug targets.

They discovered that people in Puerto Rico are more prone to Alzheimer’s, and part of this may be due to a genetic variant they uncovered.

There are approximately 6 million Alzheimer’s patients in the United States, and its prevalence is estimated to rise to almost 14 million by 2050. It is the most common type of dementia in the elderly and gradually destroys memory and thinking skills. There is no cure and the effectiveness of current treatments is limited.

One of the groups the researchers studied is the population of Puerto Rico, which makes up the second largest Hispanic group in the continental United States. It is 12.5%. It ranks fifth among the causes of death over the age of 65 in the United States, while in Puerto Rico it ranks fourth in the same age group.

More than three decades ago, while at Duke University, Alzheimer’s genetic research pioneer Margaret Pericak-Vance began trying to include more diverse populations in research.

Margaret Pericak-Vance.

Margaret Pericak-Vance.

At the time, most of the genetically based studies of Alzheimer’s were conducted in non-Hispanic white populations of European descent, largely disregarding the Hispanic and African ancestry populations.

Pericak-Vance, director of the John P. Hussman Institute for Human Genomics at Miami Miller University School of Medicine, said, “It wasn’t done. But even back then, we thought it had to be important.”

He now leads the Hussman Institute, which is building a large genetic database to study the characteristics of Alzheimer’s and genetic variations between Hispanic communities and those of African ancestry.

Their research helps fill a huge gap in minority research and could play an important role in the development of Alzheimer’s medicine.

“A genetic target that pharmaceutical companies are interested in is twice as likely to be successful therapeutically as non-genetic targets,” Pericak-Vance said.

The Hussman Institute is one of the top programs funded by the National Institute on Aging, part of the National Institutes of Health in the USA.

APOE4, a variant of the APOE gene, is considered the most important genetic risk factor for late-onset Alzheimer’s, and most studies initially only included people of European descent.

“We found that the risk was different when we started looking at different groups,” Pericak-Vance said of the findings they published in 2018, based on a study of the genomes of different groups and APOE. “For example, the risk was lower among individuals of African descent or some African descent.”

“This paper that we published made people see that ancestry is important and that we need to include different populations in the research,” he said.

D., an adjunct scientist at the Hussman Institute studying Alzheimer’s disease in Hispanic populations. Katrina Celis has spent the last 13 years focusing on genetic research.

“Being from an underdeveloped country, I was faced with and understood the need to include and represent different populations in genetic studies,” said Celis, who is originally from Venezuela. “I am focused on increasing genetic research participation from diverse populations, particularly Hispanic Latino communities.”

Katrina Celis.  (Courtesy of the John P. Hussman Human Genomics Institute)

Katrina Celis. (Courtesy of the John P. Hussman Human Genomics Institute)

Celis, a neurologist and principal investigator from the Universidad Central del Caribe in Bayamón, Puerto Rico. Collaborating with Briseida Feliciano-Astacio.

Celis and Feliciano-Astacio and the team at the Hussman Institute are studying extended families in Puerto Rico and what they call “multiplex families,” that is, individuals with more than two or three Alzheimer’s patients.

Feliciano-Astacio said the island’s aging population is struggling because many young Puerto Ricans have left the country due to the economic situation.

“There are many older people who are lonely,” she said, adding that it affects all socioeconomic backgrounds.

Celis is also focusing on a second project examining chromosome 14, which contains a well-known gene they have seen in early-onset Alzheimer’s. She said she is trying to identify the molecular mechanisms driving this particular case and the broad age range of onset they see in individuals carrying this particular genetic variant.

A variant found only among the Hispanic Caribbean

Dr.  Katrina Celis, Director of Research Support Larry Adams, and Dr.  Parker Bussies prepares to see Alzheimer's patients and their families in Puerto Rico for PRADI.  (Courtesy of the John P. Hussman Human Genomics Institute)

Dr. Katrina Celis, Director of Research Support Larry Adams, and Dr. Parker Bussies prepares to see Alzheimer’s patients and their families in Puerto Rico for PRADI. (Courtesy of the John P. Hussman Human Genomics Institute)

Puerto Ricans are a mixed population and their genetic ancestry consists mostly of European, African, and Native American or American ancestry.

“We are the first group to identify that this variant is actually in African ancestry,” Celis said of the variant on chromosome 14.

“We determined that the particular region that harbors this variant associated with Alzheimer’s disease risk is rooted in African ancestral backgrounds,” Celis said. “However, this particular variant was only found in Caribbean Hispanic individuals, mostly of Puerto Rican origin, known in the genetic world as a founder mutation, which means that after colonization there was something on the island that created this type of variant. The genetic information of these individuals.”

Celis and Pericak-Vance agree that the only way forward is to include more diverse populations.

Pericak-Vance adds, “Inclusion and awareness are essential to guiding precision medicine in diverse populations.” Said.

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