HLA-E regulatory and coding region variability and haplotypes in a Brazilian population sample

Area of Science:

• Immunogenetics
• Molecular Biology
• Human Genetics

Background:

• The Human Leukocyte Antigen-E (HLA-E) gene is a non-classical MHC class I molecule with a conserved structure and broad tissue expression.
• HLA-E plays a crucial role in immune regulation by interacting with Natural Killer (NK) cell and T cell receptors, modulating immune responses.
• Variations in HLA-E's regulatory and coding regions can impact its expression and function, influencing immune interactions.

Purpose of the Study:

• To comprehensively analyze the genetic variability of the HLA-E gene, including its regulatory (promoter, 3'UTR) and coding segments (with introns).
• To characterize the haplotype patterns and identify novel alleles within the HLA-E gene in a diverse Brazilian population.
• To investigate the association between different HLA-E regulatory and coding haplotypes and their implications for HLA-E molecule diversity.

Main Methods:

• Employed massively parallel sequencing to analyze approximately 7kb of the HLA-E gene in 420 Brazilian samples.
• Detected and characterized variable sites, promoter sequences, coding sequences (including new alleles), and 3'UTR haplotypes.
• Analyzed the association patterns between promoter, coding, and 3'UTR haplotypes.

Main Results:

• Identified 63 variable sites and 75 extended haplotypes within the HLA-E gene.
• Discovered 37 distinct promoter sequences, 27 coding sequences (15 novel HLA-E alleles), and 12 3'UTR haplotypes.
• Found that despite numerous alleles, most encode only two main HLA-E molecules (E*01:01 and E*01:03), comprising ~90% of the total.
• Observed a non-straightforward association between promoter, coding, and 3'UTR haplotypes, with the distal promoter being the most variable segment.

Conclusions:

• The HLA-E gene exhibits substantial allelic diversity, particularly in its promoter region, but encodes a limited number of functional protein molecules.
• The complex haplotype associations suggest regulatory elements may significantly influence HLA-E expression patterns.
• Further research is needed to elucidate how identified variations in regulatory and coding segments affect HLA-E gene expression and immune function.