Figure 3. Smarcal1-deficient B cells have increased rates of replication fork collapse with Myc dysregulation.

B cells from Smarcal1^+/+ Eμ-myc, Smarcal1^+/Δ Eμ-myc, and Smarcal1^Δ/Δ Eμ-myc mice were purified from bone marrow (A-C, G, I) or spleen (K, M). Pro-B cell cultures from Smarcal1^+/+, Smarcal1^+/Δ, and Smarcal1^Δ/Δ mice expressing MycER (D-F, H, J, L, N) with MycER activated by the addition of 4-hydroxytamoxifen (4-OHT) for 8 hours. (A, D) Design of DNA fiber labeling experiments and images of representative fiber tracks. B, E) Quantification of total fiber length in purified Eμ-myc B cells (B) and MycER pro-B cells (E); median indicated with red bar. C, F) Fiber length frequencies from (B) and (E), respectively. G, H) Quantification of DNA fibers that only incorporated IdU from Eμ-myc B cells (G) and MycER pro-B cells (H); SEM. I, J) Ratios of measured CldU track lengths from left and right moving forks from the same replication origin from Eμ-myc B cells (I) and MycER pro-B cells (J); median indicated with red bar. K, L) Quantification of immunofluorescence of γH2AX foci in Eμ-myc B cells (K) and MycER pro-B cells (L); SEM. M, N) Box-and-whisker plots of tail moments of Eμ-myc B cells (M) and MycER pro-B cells (N). Line is the median, boxes are the 25^th and 75^th percentiles, whiskers are the 5^th and 95^th percentiles. The total number (n) of fibers (B, E), replication structures (G-J), or cells (K-N) analyzed is indicated. All data are from 2–3 independent experiments. One-way ANOVA with Bonferroni correction (B, E, M, N, I, J) or chi-square test (G, H, K, L); *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001.