Balancing Selection at the Human Defensin β-1 Promoter
Author Information
Author(s): Cagliani Rachele, Fumagalli Matteo, Riva Stefania, Pozzoli Uberto, Comi Giacomo P, Menozzi Giorgia, Bresolin Nereo, Sironi Manuela
Primary Institution: Scientific Institute IRCCS E. Medea
Hypothesis
Does the human defensin β-1 promoter region show evidence of balancing selection across different populations?
Conclusion
The DEFB1 promoter region exhibits strong molecular signatures of long-term balancing selection, suggesting that alleles conferring resistance to pathogens in ancient settings are now associated with susceptibility to atopic disorders.
Supporting Evidence
- High levels of nucleotide variation were observed in the DEFB1 promoter region across all populations studied.
- A significant departure from the expectation of evolutionary neutrality was found in all populations.
- The two major haplotype clades of DEFB1 separated around 4.5 million years ago.
- Balancing selection is thought to be extremely rare outside major histocompatibility complex genes.
- DEFB1 variants are associated with resistance to pathogens but also with susceptibility to atopic disorders.
- Population differentiation was low, indicating balancing selection may be acting on this gene.
- Significant results were obtained in pairwise HKA tests comparing DEFB1 with other innate immunity genes.
- Trans-specific polymorphisms were identified, suggesting long-term balancing selection.
Takeaway
Scientists studied a part of our DNA that helps fight germs and found that it has been shaped by evolution to help us survive diseases, but it might also make us more likely to have allergies today.
Methodology
The study involved sequencing the DEFB1 promoter region in 83 individuals from six different populations and analyzing the genetic variation and haplotype structure.
Potential Biases
Potential biases may arise from the selection of populations and the focus on specific genetic variants.
Limitations
The study's conclusions may be influenced by demographic history, which complicates the interpretation of balancing selection signatures.
Participant Demographics
Participants included individuals from Yoruba, Asian, South American Indian, and Australian Aboriginal backgrounds.
Statistical Information
P-Value
0.0018
Statistical Significance
p<0.05
Digital Object Identifier (DOI)
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