P2RX4 and amyotrophic lateral sclerosis: Our results revealed that P2X4 expression initially restricted to MNs (P75) in SOD1 or SOD1:P2X4KI increased during the symptomatic phase of ALS (P100) but only in microglia within the spinal cord likely due to a de novo expression of P2X4 in activated microglia as described in several pathological conditions [43, 61, 83].