Knockdown of liver CFD by AAV8‐TBG‐shCFD significantly restrained CD9 ablation‐induced hepatic steatosis, including the alteration of BW, LW, LW/BW, TG content and fatty acid synthesis and oxidation related genes and proteins under HFD condition (Figure 3E‐H; Figure S4, Supporting Information). The gene discussed is CFD; the disease is fatty liver disease.