Analysis of bone marrow pro–B cells in SCID and Eμ-A1 SCID mice.

(A) Expression of mRNA for genes required for pre–B-cell development in 6-week-old mice. Bone marrow RNA was amplified using RT-PCR under semiquantitative conditions. Actin mRNA was amplified in parallel as a loading control. Eμ-A1 mRNA transcript is specific for the transgene. (B) Cell-cycle analysis of pro–B cells. Analysis of DNA content by DAPI staining was gated on B220⁺ cells. Percentages of cells in S and G2+M phases of the cell cycle were determined using FlowJo software.