I generated Hela-KRAB-dCas9 stable cell line, and to validate dCas9 activity, I introduced two sgRNA expressing vectors driven by either hU6 or mU6 promoter. I found that the mU6 promoter driven vector did show any knock down effect, but the hU6 one did. I wonder if mU6 promotor is really inactive in Hela cell, and whether mU6 promoter can be active in some human cell lines. Any one has this information? So many thanks!!!