Figure 2.

Identification of CTCF binding sites in the Csn locus and generation of mice lacking individual sites. (A) Binding of CTCF to sites A and C was detected across non-mammary cells (rectangles with solid lines) while CTCF binding to sites B and D was preferentially observed in mammary tissue (rectangles with dotted lines). (B) Sequences of the four CTCF binding sites in the mouse genome and upon CRISPR/Cas9 gene editing. CTCF binding motifs are depicted in yellow and their sequences are in bold. While sites A, C and D contain classical motifs (CCCTC), site B contains an extended motif (CCN(C/G)N(A/C/T)G(A/G)(T/G)GG(C/A/T)(G/A)(C/G) (69,70). sgRNA sequences are underlined, and deleted nucleotides are indicated as dashes. CTCF binding sequences and deletion sizes are shown. (C) CTCF ChIP-seq data confirmed loss of CTCF binding in mutant mammary tissues.