P4HB and amyotrophic lateral sclerosis: Interestingly, mutations in PDIA3 and P4HB genes have been related to motor neuron dysfunction.40, 41 OS9, instead, has been demonstrated to be involved in the degradation of hypoxia‐inducible factor 1alpha,53 a key factor in the hypoxic stress sensor pathway which is impaired in motor neurons of ALS mouse models.54 It is important to note that none of the ER stress genes correlated with a motor neuron marker in SALS cases in the motor cortex.