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. 2025 Dec 11;17:751. doi: 10.1038/s41467-025-67438-5

Fig. 1. CTCF-Nm mutation impairs distal Vκ utilization and exhibits differential effects on proximal deletional and inversional Vκ joining.

Fig. 1

a Schematic of the murine Igκ locus (not to scale). Approximately100 Vκ segments span 3.15 Mb in both forward (blue, deletional-oriented) and reverse (red, inversional-oriented) orientations. A V-J intergenic region containing the Cer and Sis elements separates the Vκs from the downstream Jκs (orange) and constant (gray) region. Pink and purple trapezoids denote forward and reverse CTCF sites, and three enhancers (orange ovals) are positioned downstream of the Jκs. b Left, HTGTS-V(D)J-Seq analysis of Vκ usage frequency in WT (top) and CTCF-Nm (bottom) v-Abl pro-B cells. Each Vκ utilization is shown as mean percentage of total VκJκ1 junctions ± SD from three independent replicates. Del stands for deletional joining and Inv stands for inversional joining. Right, summary of deletional and inversional Vκ usage in proximal versus middle/distal Vκ regions in WT and CTCF-Nm mutants. c,d Frequency of individual deletional Vκ usage (c) and inversional Vκ usage (d) in the indicated proximal Vκ region in WT and CTCF-Nm cells. Data represents mean ± SD from three independent replicates. All P values were calculated using unpaired, two-tailed Student’s t test.