SPAST and neurodegenerative disease: Some protein-encoding HSP genes, including ARL6IP1, REEP1, ALT1, and SPAST, have been identified as RTNs localized in the ER membrane (Hübner and Kurth, 2014; Voeltz et al., 2006); these play a critical role in shaping the ER, connecting intracellular membrane-bound organelles, and are intrinsic in neurodegenerative disease pathogenesis (Chiurchiù et al., 2014; Pradhan and Das, 2021).