Figure 1.

Pax5 induces D_H–J_H and V_H–DJ_H rearrangements of the IgH locus in thymocytes. (A) Schematic diagram of the V_H gene cluster of the IgH locus. Only the V_H gene families analyzed are shown together with their transcriptional direction (arrow) and distal or proximal position within the V_H gene cluster. (B) PCR detection of D_H–J_H and different V_H–DJ_H rearrangements in Ik^Pax5/+ and Ik^neo/+ thymocytes (pro-T [DN] and pre-T [DP] cells) as well as in bone marrow Pax5^+/+ and Pax5^–/– pro-B cells, which were directly sorted from 2-week-old mice. Three-fold serial DNA dilutions were analyzed by PCR. Input DNA was normalized by amplification of a PCR fragment from the IgH Cμ regions, and DNA of the stromal ST2 cells was used as negative control. Numbers to the left indicate rearrangements to the J_H1, J_H2, and J_H3 segments. (C) Quantitation of D_H–J_H recombination in sorted pro-B and pre-T cells. D_H–J_H rearrangements were analyzed by PCR in three independent preparations of sorted cells of the indicated genotypes. The average recombination frequency with its standard deviation is shown as relative percentage of the rearrangements detected in wild-type (wt) pro-B cells.