Figure 2: L1 retrotransposons upstream to VH genes promote somatic hypermutation in vivo.
(A-C) (A) Schematic of WT mice that endogenously possess L1s upstream to VH1–11 and engineered VH1–11 L1 KO mice lacking L1s upstream to VH1–11. Spleen or PP GC B cells were sorted from immunized mice. (B) Point mutation frequency for (left) all bases or (right) AID hotspot motifs across recombined VH1–11(D)JH sequences from spleen GC B cells from WT, VH1–11 L1 KO, and AID KO mice. (C) Representative SHM profiles for immunized mouse spleen GC B cells, where the x-axis represents only VH1–11(D)JH sequences, with AID hotspot motifs (pink dots) and complementarity-determining region boundaries (vertical dashed lines).
(D-F) Same as (A-C), but instead using VH1–64 L1 KO mice, focusing on recombined VH1–64(D)JH hypermutation.
(G-I) Same as (A-C), but instead using VH1–47 L1 KO mice, focusing on recombined VH1–47(D)JH hypermutation.
(J-L) Same as (A-C), but instead using VH9–4 L1 KO mice, focusing on recombined VH9–4(D)JH hypermutation.
(M) Point mutation frequency from GC B cells, using recombined VH1–12 or recombined VH1–9, isolated from immunized WT and VH1–11 L1 KO mice. Top allele, WT mouse. Bottom allele, L1 KO mouse.
(N) Same as (M), but instead using VH1–64 L1 KO mice, focusing on hypermutation of recombined VH genes flanking VH1–64.
(O) Same as (M), but instead using VH1–47 L1 KO mice, focusing on hypermutation of recombined VH genes flanking VH1–47.
(P) Same as (M), but instead using VH9–4 L1 KO mice, focusing on hypermutation of recombined VH genes flanking VH9–4.
For all plots, data are presented as mean ± SEM from at least three independent experiments, with p-values calculated by paired two-sided t-test. ****p ≤ 0.0001, ***p ≤ 0.001, p ≤ 0.01; ns, not significant.