Immunofluorescence of MATR3 was performed using HAP1 wild-type and MATR3 KO cells that were transfected with a green or a far-red fluorescent dye, respectively. Post-transfection, WT and KO cells were mixed and plated to a 1:1 ratio on coverslips as a mosaic and incubated for 24 hrs. Cells were fixed in 4% PFA (in PBS) for 15 min; cells were permeabilized with 0.1% Triton X-100 for 10 min at RT and blocked with PBS with 5% BSA, 5% goat serum, and 0.01% Triton X-100 for 30 min. Cells were stained with the MATR3 recombinant monoclonal antibody (Product # MA5-34642) at a 1:1,000 dilution overnight at 4°C. Secondary antibody incubation was performed using 1 µg/mL of Goat anti-Rabbit IgG (H+L) Highly Cross-Adsorbed Secondary Antibody, Alexa Fluor 555 antibody (Product # A21429) for 1 hr. Imaging was performed with a 40X oil objective and analysis was performed using Image J. Cell image represents a single focal plane; WT and KO cells are outlined with a yellow (WT) or magenta (KO) dashed line. Data courtesy of YCharOS Inc., an open science company with the mission of characterizing commercially available antibodies using knockout validation.