Table 4.

Cellular models are involved in the pathogenesis of HSP, including the genes involved and HSP subtypes in each category.

Cellular Models Involved in HSP Pathogenesis	Proteins	SPG Forms
1. Organelle’s morphogenesis/membrane structure Microtubule/membrane structure-associated ATPase ER tubules linking GTPase ER morphology organizer               Modulating lipid metabolism and droplet formation Regenerating lysosome Adaptor proteins Tubule formation in endosomes Defects in organelles morphology inducing axonal pathology (lysosome and ER endosomes)	SPAST     Atlastin   SPAST Atlastin REEP1 Reticulon 2 ARL6IP1 RAB3GAP2 Protrudin REEP2   AIP4/Spartin SLC33A1   Spatacsin Spastizin   AP-4 for trafficking precursors of amyloids     Strumpellin   REEP1 Atlastin Spastizin Spatacsin Strumpellin	SPG4     SPG3A   SPG4 SPG3A SPG31 SPG12 SPG61 SPG69 SPG33 SPG72   SPG20 SPG43   SPG11 SPG15   SPG47 SPG50 SPG52   SPG8   SPG31 SPG3A SPG15 SPG11 SPG8
2. Bone morphogenic proteins	NIPA1 Atlastin-1 Spastin Acetyl-CoA transporter	SPG6 SPG42 SPG3A SPG4
3. Motor proteins transportation	KIF5A KIF1C KIF1A	SPG10 SPG58 SPG30
4. Mitochondrial failure	Paraplegin HSP60 IBA57 Spartin	SPG7 SPG13 SPG74/SPG77 SPG20
5. Axon elongation path	L1CAM	SPG1
6. Myelination errors	PLP1 GJC2 MAG	SPG2 SPG44 SPG75
7. Nucleotide’s metabolism	AMPD2 NT5C2 ENTPD1	SPG63 SPG65 SPG64