Hereditary spastic paraplegia type 52 (SPG52) is an ultra-rare neurological disorder characterized by lower limb spasticity, weakness, global developmental delay, intellectual disability, and seizures. SPG52 is caused by biallelic mutations in the AP4s1 gene, which encodes a subunit of the adaptor protein complex 4 (AP-4). However, its pathophysiology is poorly understood. Currently, there is no cure nor treatment. We believe that gene therapy aimed at restoring AP4s1 expression is a rational therapeutic approach to ameliorate the disease phenotype. We have developed a knock-out (KO) mouse model using CRISPR-Cas technology targeted to abolish AP4s1 expression. Cognitive and physical skills batteries have been performed and KO mice show decreased motor coordination and impaired memory while having regular exploratory behavior. Distinctive hallmarks described in patients have been observed by magnetic resonance imaging, electrophysiology, and clasping test. Presently, we are treating KO animals systemically with a neurotropic AAV vector carrying a correct copy of the AP4s1 gene at different ages and assessing phenotype rescue. Moreover, we have characterized and treated patient-derived fibroblasts with an AAV vector carrying the therapeutic gene and confirmed our therapeutic approach effectiveness by verifying AP-4 complex restoration. Finally, to develop a relevant human model of the disease, we generated patient-specific induced pluripotent stem cells (iPSCs) that upon differentiation recapitulate aspects of the disease’s pathophysiology and can be used to test the efficacy of our novel gene therapy strategy. Altogether, generating both models with phenotypes that resemble human pathology is crucial to elucidate SPG52 pathogenesis and validate our gene therapy approach.