Chromatin was sonicated to an average size of 500 bp, then 1/25 of total chromatin was set aside (input). The rest of the chromatin was incubated overnight with rabbit anti-CTCF antibody (Cell Signaling Technology) or rabbit IgG, as a control. CTCF-bound chromatin fragments were then purified using magnetic Dynabeads (Invitrogen), and crosslinking was reversed. For telencepalon samples, libraries were prepared following New England Biolabs NEB ChIP-Seq Library Prep Kit for Illumina, for MGE libraries were prepared using the NEBNext Ultra II DNA Library Prep Kit for Illumina