CD9 and nutritional disorder: Further analysis identified four key proteins with substantial changes, representing diverse functional categories relevant to the astrocyte response to iron deficiency: tripeptidyl-peptidase 2 (Tpp2; 2.14-fold increase), citrate synthase (Cs; 2.03-fold increase), CD9 antigen (Cd9; 0.44-fold decrease), and ferritin light chain 1 (Ftl1; 0.48-fold decrease).