1. Ebf1 heterozygosity results in increased DNA damage in pro-B cells and their synergistic transformation by Pax5 haploinsufficiency
by Mahadesh A. J. Prasad, Jonas Ungerbäck, Josefine Åhsberg, Rajesh Somasundaram, Tobias Strid, Malin Larsson, Robert Månsson, Ayla De Paepe, Henrik Lilljebjörn, Thoas Fioretos, James Hagman, and Mikael Sigvardsson
Blood
Volume 125(26):
June 25, 2015
©2015 by American Society of Hematology

2. Heterozygous loss of Ebf1 results in increased levels of phosphorylated H2AX in B-cell progenitors.
Heterozygous loss of Ebf1 results in increased levels of phosphorylated H2AX in B-cell progenitors. (A) Representative western blot out of 3 detecting γH2AX and glyceraldehyde-3-phosphate dehydrogenase from in vitro cultured Wt or Ebf1+/− pro-B cells. (Lower) Quantification of the signal intensity normalized to the Wt control and represents 3 experiments. The data shown in band intensity for mean ± standard deviation (SD) and statistical analysis was performed using an unpaired Student t test: ***P < .001 (B) Graphs over the relative MFI obtained by flow cytmetric analysis to detect γH2AX and indirect flow analysis of phosphorylated Chk1 (pChk1) and phosphorylated Chk2 (pCHK2) in in vitro-cultured Wt or Ebf1+/− pro-B cells. The data are normalized toward the Wt control and expressed in fold MFI that represents 3 independent experiments. The statistical analysis was done using an unpaired t test. Mean ± SD; **P < .01 and *P < .05 (C) Immunofluorescence analysis of phosphorylated and nonphosphorylated H2AX (total H2AX) in in vitro-cultured Wt or Ebf1+/− pro-B cells detected by using rabbit γH2AX monoclonal antibody or rabbit monoclonal total H2AX antibody followed by a specific anti-Alexa Fluor 594 secondary antibody. The nuclei were subsequently stained with DAPI, and the images were captured using an LM Zeiss upright confocal microscope. The quantification panel next to the image displaying the signal intensity was collected from 3 experiments. The statistical analysis was performed using an unpaired t test, and results are plotted as change in fold integrated density compared with Wt; **P < .01 and ***P < (D) Diagram with relative MFI obtained by flow cytometric analysis to detect γH2AX, in ex vivo-isolated Wt or Ebf1+/− pro-B cells. The data are normalized toward the Wt control and represent 3 experiments, and an unpaired t test was performed. Mean ± SD; **P < .01 (E) Diagrams displaying quantitative RT-PCR data from in vitro-cultured Wt or Ebf1+/− pro-B cells. The data are normalized to the expression of HPRT in triplicate PCR reactions. An unpaired Student t test was performed for statistical analysis. ***P < Data represent 3 independent experiments as mean ± SD. (F) Frequency of AnnexinV+ cells as estimated by flow cytometric analysis from in vitro-cultured Wt or Ebf1+/− pro-B cells. The cells were gated on a lymphoid gate for live cells. The data represent 5 experiments. The error bar in the panels indicate mean ± SD, and statistical analysis was performed using the Student t test. ***P < (G) Cell cycle status of Wt or Ebf1+/− pro-B cells using Ki67 and DAPI staining. G0 cells were scored as Ki67−DAPIlow, G1 Ki67+ DAPIlow, and SG2M as Ki67+DAPIhigh. Mean ± SD and statistical analysis was performed using the Student t test. *P < .05.
Mahadesh A. J. Prasad et al. Blood 2015;125:
©2015 by American Society of Hematology

3. Heterozygous loss of Ebf1 results in increased DNA damage after UV exposure of B-cell progenitors.
Heterozygous loss of Ebf1 results in increased DNA damage after UV exposure of B-cell progenitors. (A) Relative MFI obtained by flow cytometric analysis to detect γH2AX in in vitro-cultivated primary Wt or Ebf1+/− pro-B cells 16 hours after UV exposure. The data are normalized toward the Wt control and represent 3 experiments, The statistics were performed using an unpaired t test; the error bar represents mean ± SD. ***P < (B) Immunohistochemical staining of phosphorylated H2AX (γH2AX) in in vitro-cultured Wt or Ebf1+/− pro-B cells 16 hours after UV exposure. DAPI was used to stain the nucleus. (Lower) Quantification of the signal intensity collected from 3 experiments. The representation of fold-integrated density is based on an unpaired t test with error bars representing mean ± SD. ***P < (C) Representative pictures of comet assays performed 16 hours after UV exposure of in in vitro-cultivated primary Wt or Ebf1+/− pro-B cells. (D) Quantitative RT-PCR data from in vitro-cultured Wt or Ebf1+/− pro-B cells before and 16 hours after UV exposure. The data are normalized to the expression of HPRT in triplicate PCR reactions and represent 3 independent experiments. The Student t test represents statistical analysis. ****P < (E) Frequency of annexinV+ cells as estimated by flow cytometric analysis from in vitro-cultured Wt or Ebf1+/− pro-B cells. The cells were gated on a lymphoid gate for live cells. The error bars in the diagrams indicate mean ± SD, and statistical analysis was performed using an unpaired Student t test. **P < .01.
Mahadesh A. J. Prasad et al. Blood 2015;125:
©2015 by American Society of Hematology

4. Heterozygous loss of Ebf1 results in lower levels of Rad51 in B-cell progenitors.
Heterozygous loss of Ebf1 results in lower levels of Rad51 in B-cell progenitors. (A) Quantitative RT-PCR data from in vitro-cultured Wt or Ebf1+/− pro-B cells. The data are normalized to the expression of HPRT in triplicate PCR reactions and represent 3 independent experiments. The Student t test was performed to check the statistical significance. **P < .01 and *P < .05. (B) Immunofluorescence staining of γH2AX (rabbit) and mouse Rad51 in in vitro-cultured Wt or Ebf1+/− pro-B cells followed by the specific anti-Alexa Fluor 594 (γH2AX) and anti-Alex Fluor 488 secondary antibody (Rad51). DAPI was used to stain the nucleus. The panel adjacent to each IF image shows a quantification of the signal intensity collected from 3 experiments, and quantification is represented as fold integrated density with statistical significant value: *P < .05 for γH2AX and ***P < .001 for Rad51. (C) Immunohistochemical staining of Rad51 in in vitro-cultured Wt or Ebf1+/− pro-B cells 16 hours after UV exposure. DAPI was used to stain the nucleus. The data were collected from 3 experiments, and foci formation was counted from 3 cells from 3 different experiments. The error bars in the diagrams indicate mean ± SD, and statistical analysis was performed using the Student t test, with P < .001.
Mahadesh A. J. Prasad et al. Blood 2015;125:
©2015 by American Society of Hematology

5. Combined heterozygous loss of Ebf1 and Pax5 results in development of disease and increased mortality.
Combined heterozygous loss of Ebf1 and Pax5 results in development of disease and increased mortality. (A) Kaplan-Meier curves describing the 40-week survival of Wt, Ebf1+/−, Pax5+/−, and Pax5+/−Ebf1+/− mice. A drop in the curve describes unknown cause of death or development of swollen lymph nodes and subsequent euthanasia due to animal protection regulations. Mice euthanized for known reasons other than swollen lymph nodes are censored in the curves. Overall log-rank (Mantel-Cox test) P value is displayed. (B) Two enlarged, one inguinal and one brachial, lymph nodes from a Pax5+/−Ebf1+/− mouse. (C) Representative flow cytometric analysis of the cellular content of a representative lymph node (left) and the fraction of CD43high or IgM+CD19+ cells in 4 analyzed nodes (right). (D) Quantitative RT-PCR data over gene expression analysis of sorted live cells in 4 analyzed lymph nodes. Sorted Pax5+/−Ebf1+/− BM pro-B cells and lymphoid primed multipotent progenitors were used as positive and negative controls. Expression levels are presented in relation to HPRT. Data represent 1 of 2 quantitative PCR experiments using triplicate PCR reactions for estimation of expression values. (E) Immunoglobulin heavy chain VDJ analysis from 3 of the analyzed live cell populations from nodes of mice displaying peripheral pro-B cell expansion. Cultured Wt pro-B cells were included to show the rearrangement signature of a polyclonal population.
Mahadesh A. J. Prasad et al. Blood 2015;125:
©2015 by American Society of Hematology

6. Pax5+/−Ebf+/− tumor cells display molecular heterogeneity.
Pax5+/−Ebf+/− tumor cells display molecular heterogeneity. (A) Heat map over gene expression patterns in primary sorted CD19+CD43highIgM− ex vivo-analyzed BM pro-B cells from 14-week-old mice and 8 pro-B cells tumors from Pax5+/−Ebf1+/− mice. The expression pattern is based on genes differentially expressed >10-fold in any of the tumor samples compared with normal pro-B cells. Red indicates high and blue indicates low expression of mRNA. The data are collected from 2 array experiments from each cell population. (B) Quantitative PCR data generated from primary sorted live lymph node cells from a set of independently generated tumors and primary sorted BM pro-B cells. The data were normalized to the expression of Hprt, and the diagrams present 1 of 2 independent quantitative RT-PCR experiments based on triplicate quantitative RT-PCR reactions.
Mahadesh A. J. Prasad et al. Blood 2015;125:
©2015 by American Society of Hematology