TopBP1 deficiency impairs V(D)J recombination during lymphocyte development

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• Topoisomerase II-β-binding protein 1 (TopBP1) is known for its roles in DNA replication and repair.
• TopBP1 is highly expressed in lymphoid tissues, suggesting a role in immune cell development.

Purpose of the Study:

• To investigate the role of TopBP1 in lymphocyte development and V(D)J recombination.
• To elucidate the molecular mechanisms underlying TopBP1's function in immune cell maturation.

Main Methods:

• Analyzing TopBP1 expression in lymphoid tissues.
• Abrogating TopBP1 expression in developing lymphocytes.
• Assessing V(D)J rearrangement efficiency and DNA double-strand break repair.
• Utilizing γ-H2AX foci as a marker for DNA damage.
• Complementation studies with TCR αβ transgenes.

Main Results:

• TopBP1 deficiency caused developmental blocks in early lymphocyte development (pro-B cells, thymocytes).
• Aberrant V(D)J rearrangements and inefficient DNA double-strand break repair were observed in TopBP1-deficient cells.
• TopBP1 localized to V(D)J rearrangement sites, and its absence increased γ-H2AX foci.
• Developmental defects were rescued by introducing functional TCR αβ transgenes.

Conclusions:

• TopBP1 is essential for V(D)J rearrangement during the development of B, T, and iNKT cells.
• TopBP1 plays a novel and critical role in DNA repair processes vital for lymphocyte maturation.
• The findings establish TopBP1 as a key regulator in adaptive immunity development.