A novel pax5-binding regulatory element in the igκ locus

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• The immunoglobulin kappa (Igκ) locus is critical for B cell development.
• Key processes like V(D)J rearrangement and somatic hypermutations (SHM) are regulated by cis-regulatory regions (RRs).
• Three enhancers (iEκ, 3'Eκ, Ed) are known, but a DNA region upstream of iEκ and MAR was previously linked to demethylation.

Purpose of the Study:

• To characterize the DNA region upstream of iEκ and MAR, termed the demethylation (Dm) element.
• To investigate the role of the Dm element and its Pax5-binding site in Igκ locus demethylation and SHM in vivo.
• To elucidate the function of the Dm element in B cell development.

Main Methods:

• Generation of Igκ transgenes with Dm region deletions or Pax5-binding site deletions.
• Analysis of CpG demethylation in mature B cells in vivo.
• Generation of mice with a full Dm region deletion at the endogenous Igκ locus.
• Assessment of SHM in germinal center B cells in Peyer's patches.

Main Results:

• Igκ transgenes lacking the Dm region or a Pax5-binding site showed impaired CpG demethylation in mature B cells.
• Mice with a deleted Dm region exhibited reduced SHM in germinal center B cells.
• The Dm element is essential for efficient Igκ demethylation and SHM.

Conclusions:

• The Dm element is a novel cis-regulatory element that binds Pax5.
• The Dm element functions with known enhancers to regulate Igκ demethylation.
• The Dm element plays a significant role in Igκ demethylation and somatic hypermutations during B cell development.