Analysis of mutations from SCID and Omenn syndrome patients reveals the central role of the Rag2 PHD domain in regulating V(D)J recombination.

Rag2 plays an essential role in the generation of antigen receptors. Mutations that impair Rag2 function can lead to severe combined immunodeficiency (SCID), a condition characterized by complete absence of T and B cells, or Omenn syndrome (OS), a form of SCID characterized by the virtual absence of B cells and the presence of oligoclonal autoreactive T cells. Here, we present a comparative study of a panel of mutations that were identified in the noncanonical plant homeodomain (PHD) of Rag2 in patients with SCID or OS.

Distinct effects of DNA-PKcs and Artemis inactivation on signal joint formation in vivo.

The assembly of functional immune receptor genes via V(D)J recombination in developing lymphocytes generates DNA double-stranded breaks intermediates that are repaired by non-homologous end joining (NHEJ). This repair pathway requires the sequential recruitment and activation onto coding and signal DNA ends of several proteins, including the DNA-dependent protein kinase and the nuclease Artemis. Artemis activity, triggered by the DNA-dependent protein kinase, is necessary to process the genes hairpin-sealed coding ends but appears dispensable for the ligation of the reciprocal phosphorylated, blunt-ended signal ends into a signal joint.

Collaboration of homologous recombination and nonhomologous end-joining factors for the survival and integrity of mice and cells.

Homologous recombination (HR) and nonhomologous end-joining (NHEJ) are mechanistically distinct DNA repair pathways that contribute substantially to double-strand break (DSB) repair in mammalian cells. We have combined mutations in factors from both repair pathways, the HR protein Rad54 and the DNA-end-binding factor Ku80, which has a role in NHEJ. Rad54(-/-)Ku80(-/-) mice were severely compromised in their survival, such that fewer double mutants were born than expected, and only a small proportion of those born reached adulthood.

Allelic exclusion at the TCR delta locus and commitment to gamma delta lineage: different modalities apply to distinct human gamma delta subsets.

Expression of a beta-chain, as a pre-TCR, in T cell precursors prevents further rearrangements on the alternate beta allele through a strict allelic exclusion process and enables precursors to undergo differentiation. However, whether allelic exclusion applies to the TCR delta locus is unknown and the role of the gamma delta TCR in gamma delta lineage commitment is still unclear. Through the analysis of the rearrangement status of the TCR gamma, delta, and beta loci in human gamma delta T cell clones, expressing either the TCR V delta 1 or V delta 2 variable regions, we show that the rate of partial rearrangements at the delta locus is consistent with an allelic exclusion process.