library_construction_protocol: Mice were deeply anesthetized with isoflurane. Sections of 1 mm spanning V1 were collected in an adult mouse brain matrix (Alto) on ice, and V1 was microdissected. After dissecting samples, V1 tissue was transferred to a 1.5 mL tube containing 350 μL of cold homogenization buffer (250 mM sucrose, 25 mM KCl, 5 mM MgCl2, 20 mM tricine-KOH pH 7.8 supplemented with 1X PIC, 1 mM DTT, 0.15 mM spermine and 0.5 mM spermidine). The tissue was dounced in a 2 mL glass homogenizer (Sigma D8938) with a loose pestle for 20 strokes. Samples were supplemented with 0.3% IGEPAL CA-630 and further dounced for an additional 10 strokes with a tight pestle. Homogenate was filtered through a small 40-μm strainer (pluriSelect 43-10040-50) into a 1.5 mL tube before diluting 1:1 with homogenization buffer and adding DRAQ5 (Abcam ab108410) at a 1:500 dilution. Nuclei were then sorted by GFP and/or DRAQ5 signal using the Sony SH800S Cell Sorter (purity mode) with a 100-μm sorting chip. For ATAC-seq, 50,000 DRAQ5+/GFP+ events were collected into 1 mL of cold ATAC-RSB (10 mM Tris-HCl pH 7.5, 10 mM NaCl, 3 mM MgCl2). After sorting nuclei into ATAC-RSB, 0.1% Tween-20 was added, and the nuclei were centrifuged at 500g for 10 min at 4°C. The nuclei pellet was directly resuspended in the transposition reaction mix, according to the OMNI-ATAC protocol. A 1 μL volume of homemade Tn5 enzyme was used in the transposition reaction. Libraries were prepared with NEBNext High-Fidelity 2X PCR Master Mix (NEB M0541L), following the standard protocol. After an initial five cycles of amplification, another four cycles were added to achieve optimal library concentration, based on qPCR quantification. Libraries were then size-selected (0.5X-1.8X) twice with AMPure XP beads (Beckman Coulter A63880) and sequenced paired-end on an Illumina NextSeq 500 using a 75-cycle kit.