Fig. 6
From: Mutations in topoisomerase IIβ result in a B cell immunodeficiency
Heterozygous mutation in Top2b negatively affects B-cell development beyond haploinsufficiency. Expression of mutant Top2b (n = 7) results in reduced CD19+ B cells (a) in peripheral blood compared to wild-type (n = 6) or hemizygous mice (n = 6), while T cells (b) are unaffected.(shown as mean ± SEM, *p < 0.05, **p < 0.005, two-tailed Student’s t test). c qPCR analysis of kappa-deleting recombination excision circles demonstrates that B cells isolated from Top2b+/EE587E (n = 7) or Top2b+/− mice (n = 7) have a less robust replication history compared to wild-type mice (n = 8 mice), shown as mean ± SEM, while T-cell proliferation as measured by T-cell receptor excision circle (TREC) formation is unaffected (d), (n = 6 WT, 6 mutant and 4 hemizygous mice, performed with technical duplicates shown as mean ± SEM). *p < 0.05, **p < 0.005, one-way ANOVA. e–g Comet assay shows increased DNA strand breaks in B cells (e, f) isolated from Top2b+/EE587E mice compared to wildtype, expressed as comet tail length. T cells (g) are not affected (n = 3 mice per group, 10 images per mouse (X40); *p < 0.05; ****p < 0.0001, by Kruskal–Wallis test (f), or nonsignificant (n.s.) by Student’s t test (g)). h, i Expression of Top2b is elevated in wild-type B cells compared to wild-type T cells by RT-qPCR (h, n = 5 mice, performed in technical triplicates, shown as mean ± SEM, *p < 0.05, two-tailed Student’s t test), and immunoblot (i, protein isolated from B and T cells from three wild-type mice, representative of four experiments; source data are provided as a Source Data file)
