CARM1/PRMT6 double knockout embryos are smaller compared with single knockout. CARM1/PRMT6 double knockout embryos and their littermates at age E13.5 (A) and E18.5 (B) were obtained from cross-breeding CARM1+/−PRMT6+/− mice. C, primary MEFs were generated from the WT, CARM1 KO, PRMT6 KO, and DKO embryos. The gross levels of ADMA, MMA, SDMA, and CARM1 substrates (indicated by H3R17me2a antibody) are shown. *, highlighted ADMA signal only lost in CARM1/PRMT6 double knockout MEFs.