A recent study examines how African and European genetic ancestries impact the risk of brain disorders in Black Americans. TEK Image/Science Photo Library/Getty Images
June 13, 2024 Story by: Editor
Black Americans face a higher risk of certain neurological disorders, a disparity that has puzzled researchers. A recent study in Baltimore examined the postmortem brains of 151 individuals who identified as Black or African American to shed light on this issue.
Researchers analyzed the impact of African and European ancestries on these individuals. They discovered that genes linked to African ancestry might increase the risk of Alzheimer’s disease and stroke by affecting certain brain cells. Conversely, genes tied to European ancestry seemed to influence other brain cells, potentially raising the risk of Parkinson’s disease, a disorder less prevalent among Black Americans.
The study also explored whether genetic ancestry affected neurons, crucial for memory, movement, and thinking. Despite higher rates of psychiatric disorders like schizophrenia among Black Americans, the researchers found no evidence that genetic ancestry influenced neurons. This suggests that societal factors—such as economic and psychological stress, trauma, and racial bias in diagnosis—might play a more significant role, though the study did not directly measure these factors.
Published in Nature Neuroscience, the findings mark an initial step towards addressing the increased risk associated with different ancestries, according to Dr. Kafui Dzirasa, a psychiatry professor at Duke University and an advisor to the study.
A Community Effort
Black Americans have been underrepresented in genomic studies of neurological disorders, leaving gaps in understanding how African ancestry influences disease risk and treatment response. This gap led to the creation of the African Ancestry Neuroscience Research Initiative in 2019, a collaboration involving African American community leaders, the Lieber Institute for Brain Development, Duke University, and Morgan State University.
Earning the trust of Baltimore’s Black residents was crucial for the initiative, which involved engaging prominent African American educators, businesspeople, and church leaders like Rev. Alvin Hathaway, Sr. “You had to build relationships with families and communities such that when their loved ones passed away, they were willing to donate their brains to medical research,” Dzirasa explained.
Genes vs. Environment
Gene expression, which describes how genes are activated or deactivated in cells, can be influenced by genetics, experiences, and environment. The study aimed to minimize differences due to experience and environment, attributing 15% of the differences in gene expression to these factors, while genetic ancestry accounted for more than 60%.
Ancestry appeared to most significantly impact gene expression in immune cells and cells forming blood vessel walls. This could help explain why strokes caused by blocked arteries are 50% more common in African Americans than in white individuals. Differences in immune cell responses might also clarify why African Americans are more prone to Alzheimer’s but less likely to develop Parkinson’s disease.
Neurons and Psychiatric Disorders
The study did not provide much insight into why Black Americans are about 20% more likely than white Americans to experience serious mental health issues like schizophrenia and depression. These disorders involve neurons, the brain’s gray matter cells, yet ancestry did not affect gene expression in these cells, suggesting environmental and experiential factors might be more influential.
However, Dzirasa believes there might be another explanation. Immune cells, such as microglia, which prune synaptic connections in the brain, might play a role in psychiatric disorders. Disruptions in this pruning process have been linked to schizophrenia and autism spectrum disorder.
Towards Precision Medicine
While the study used self-identified race as a starting point, it also demonstrated that racial categories are poor indicators of genetic background. Participants’ European ancestry ranged from zero to over 60 percent, underscoring the need for doctors to look beyond race when assessing disease risk.
The study highlights the importance of diverse genetic research. Understanding genes that protect individuals with certain ancestries from diseases like Parkinson’s could lead to broader protective measures.
Race, although a social construct, still provides insight into a patient’s life experience and disease risk, according to Dzirasa. However, he advocates for a future where precision medicine, based on individual genomic architecture, replaces race-based approaches.“The more optimal future is one in which we understand each person’s individual genomic architecture, and then prescribe medicines based on this,” Dzirasa says. Source: NPR
