Deacetylase activity of histone deacetylase 3 is required for productive <i>VDJ</i> recombination and B-cell development.

Abstract

Histone deacetylase 3 (HDAC3) is the catalytic component of NCoR/SMRT corepressor complexes that mediate the actions of transcription factors implicated in the regulation of B-cell development and function. We crossed <i>Hdac3</i> conditional knockout mice with <i>Mb1-Cre</i> knockin animals to delete <i>Hdac3</i> in early progenitor B cells. The spleens of <i>Hdac3</i>^F/-<i>Mb1-Cre</i>^+/- mice were virtually devoid of mature B cells, and B220⁺CD43⁺ B-cell progenitors accumulated within the bone marrow. Quantitative deep sequencing of the Ig heavy chain locus from B220⁺CD43⁺ populations identified a defect in <i>V</i>_<i>H</i><i>DJ</i>_<i>H</i> recombination with a severe reduction in productive rearrangements, which directly corresponded to the loss of pre-B cells from <i>Hdac3</i>^<i>Δ</i>/- bone marrow. For <i>Hdac3</i>^<i>Δ</i>/- B cells that did show productive <i>VDJ</i> rearrangement, there was significant skewing toward the incorporation of proximal <i>V</i>_<i>H</i> gene segments and a corresponding reduction in distal <i>V</i>_<i>H</i> gene segment use. Although transcriptional effects within these loci were modest, <i>Hdac3</i>^<i>Δ</i>/- progenitor cells displayed global changes in chromatin structure that likely hindered effective distal <i>V-DJ</i> recombination. Reintroduction of wild-type Hdac3 restored normal B-cell development, whereas an Hdac3 point mutant lacking deacetylase activity failed to complement this defect. Thus, the deacetylase activity of Hdac3 is required for the generation of mature B cells.