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Published on: September 6, 2017
Imputing amino acid polymorphisms in human leukocyte antigens
Xiaoming Jia1, Buhm Han, Suna Onengut-Gumuscu
1Harvard-MIT (Massachusetts Institute of Technology) Division of Health Sciences and Technology, Boston, Massachusetts, United States of America.
SNP2HLA is a computational tool that imputes human leukocyte antigen (HLA) alleles and amino acid variations from SNP data. Larger reference panels, not SNP density, are key for accurate HLA imputation in genetic studies.
Area of Science:
- Genetics
- Immunogenetics
- Computational Biology
Background:
- Human Leukocyte Antigen (HLA) gene variations influence disease susceptibility.
- The complex Major Histocompatibility Complex (MHC) region poses challenges for direct genotyping in large populations.
Purpose of the Study:
- To develop and evaluate SNP2HLA, a computational method for imputing HLA alleles and amino acid polymorphisms.
- To assess the impact of reference panel size and genotyping platform on imputation accuracy.
Main Methods:
- Developed the SNP2HLA computational strategy for imputing classical alleles and amino acid polymorphisms at HLA class I and II loci.
- Constructed European ancestry reference panels using HapMap-CEPH and Type 1 Diabetes Genetics Consortium (T1DGC) data.
- Imputed HLA alleles in an independent cohort (British 1958 Birth Cohort) using Affymetrix and Illumina genotyping data.
Main Results:
- Imputation accuracy is primarily dependent on the size of the reference panel, not SNP density.
- High imputation accuracy achieved: 94.7%-96.7% for four-digit HLA alleles and 98.6%-99.3% for amino acid polymorphisms.
- Demonstrated utility of SNP2HLA for fine-mapping MHC association signals, exemplified by type 1 diabetes.
Conclusions:
- SNP2HLA provides a robust method for interrogating HLA variation in existing genome-wide association study (GWAS) datasets.
- Leveraging large reference panels is crucial for accurate HLA imputation.
- Imputation at amino acid resolution aids in fine-mapping complex genetic associations within the MHC region.
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