HLA-DQA1 Gene - Structure, Function, and Clinical Significance

HLA-DQA1 encodes the alpha chain of the HLA-DQ heterodimer, a class II major histocompatibility complex (MHC) molecule expressed on antigen-presenting cells. The alpha chain (DQA) pairs with a beta chain (DQB) to form the DQ molecule, which presents exogenous peptides to CD4+ T-helper cells. HLA-DQA1 is highly polymorphic, with specific alleles strongly associated with autoimmune diseases such as celiac disease, type 1 diabetes, and rheumatoid arthritis. The gene is located within the MHC class II region on chromosome 6p21.32.

Tissue Expression

Cell Line Expression

Hotspot Mutations

Mutation functional classification

• Antigen processing and presentation (KEGG hsa04612)

• Th1 and Th2 cell differentiation (KEGG hsa04658)

• Th17 cell differentiation (KEGG hsa04659)

• Intestinal immune network for IgA production (KEGG hsa04672)

• Allograft rejection (KEGG hsa05330)

• Graft-versus-host disease (KEGG hsa05332)

• Type I diabetes mellitus (KEGG hsa04940)

• Autoimmune thyroid disease (KEGG hsa05320)

The HLA-DQA1 protein (UniProt P01909) is a 254-amino-acid type I transmembrane glycoprotein that forms the alpha chain of the HLA-DQ heterodimer. It consists of two extracellular domains (alpha1 and alpha2), a transmembrane region, and a short cytoplasmic tail. The alpha1 domain contributes to the peptide-binding groove, which accommodates peptides of 13–25 residues. Polymorphic residues in the alpha1 domain determine peptide specificity and T-cell recognition. The protein is synthesized in the endoplasmic reticulum, associates with the invariant chain (CD74), and traffics to endosomal compartments where antigen loading occurs. Surface expression is restricted to professional antigen-presenting cells (dendritic cells, macrophages, B cells) and thymic epithelial cells.