FECH and Alzheimer disease: All these results together suggest a clear difference in heme homeostasis between EOAD and LOAD neurons: In LOAD (AD APOE4 DIF) neurons, detected enzymes/proteins involved in heme synthesis (ALAS1, Figure 3A; FECH, Figure 3B) and degradation (HO-1, Figure 3C; HO-2, Figure 3D; BLVRB, Figure 3E) were all significantly reduced relative to control neurons.