For instance, as stated, it has been demonstrated that MMP9 is highly expressed by ALS-affected spinal MNs, whereas its expression is absent in Onuf’s neurons; on the contrary, the protein OPN is selectively expressed by ALS-resistant pool, while downregulated in vulnerable MNs (Kaplan et al., 2014). Here, MMP9 is linked to amyotrophic lateral sclerosis.