Results of previous studies showing the TfR1 expression in SOD1 ALS animal and cellular models are not conclusive: cellular studies report the increase of TfR1 at both mRNA and protein levels (Danzeisen et al., 2006; Hadzhieva et al., 2013), but TfR1 protein expression in cervical cord of SOD1G37R mice has been shown unchanged (Jeong et al., 2009). Here, SOD1 is linked to amyotrophic lateral sclerosis.