Figure 5. MEF2C promotes BCR rearrangement during bone marrow B lymphopoiesis.

(a) Analysis of Affymetrix microarray data shows the expression of Rag1, Rag2, Xrcc4, Xrcc6, Lig4 and Rad51 in pro-B and pre-B cells in both control and Vav-Cre Mef2c^fl/fl mice (9-months old). Loss of Mef2c compromised the expression of all these factors (n≥2). (b,c) Quantitative PCR analysis of κ and λ light chain rearrangement (n≥5 mice) in bone marrow pre-B cells, and V_H-J558 and V_H-7183 to DJ_H3 heavy chain rearrangement (n≥7) in pro-B cells (7–10-months old) revealed significantly reduced frequencies of κ and λ light chain and V_H-J558 heavy chain recombination in the absence of Mef2c. (d,e) Representative flow cytometric plots and quantification of intracellular expression of μ and κ in bone marrow B-cell progenitors from mice without irradiation and 2 weeks after 6 Gy total body irradiation shows compromised rearrangement efficiency already in steady state, and further exaggeration of the defect during stress haematopoiesis (7–10-months old, n≥10). Both male and female mice were included. Data shown are the mean±s.d. of three or more independent experiments. *P<0.05, **P<0.01 and ***P<0.001, unpaired t-test.