Leveraging pleiotropy identifies common-variant associations with selective IgA deficiency.

Area of Science:

• Immunology
• Genetics
• Human Complex Diseases

Background:

• Selective IgA deficiency (SIgAD) is the most prevalent inborn error of immunity (IEI).
• Unlike other IEIs, highly penetrant rare variants are not strongly implicated in SIgAD.
• Previous genome-wide association studies (GWAS) lacked the statistical power to detect common variants due to small sample sizes.

Purpose of the Study:

• To identify common genetic variants associated with Selective IgA deficiency.
• To investigate the genetic architecture of SIgAD and its relationship with other immune-mediated diseases.
• To strengthen the evidence for a polygenic, common-variant etiology in SIgAD.

Main Methods:

• Performed a meta-analysis of two existing genome-wide association studies (GWAS) for SIgAD.
• Utilized a conditional false discovery rate procedure, integrating SIgAD data with large GWAS of asthma, rheumatoid arthritis, and serum IgA.
• Analyzed shared genetic architecture and pleiotropy between SIgAD, serum IgA levels, and immune-mediated diseases.

Main Results:

• Identified four novel common-variant associations for SIgAD in the initial meta-analysis.
• SIgAD-associated variants showed enrichment in genes previously linked to Mendelian IEIs.
• An additional 18 variants were identified through pleiotropy analysis, bringing the total to 27 known SIgAD-associated variants.

Conclusions:

• Selective IgA deficiency has a polygenic, common-variant genetic basis.
• The findings highlight shared genetic factors between SIgAD, serum IgA levels, and other immune-mediated conditions.
• This study significantly advances the understanding of SIgAD etiology by identifying numerous common variants.