AbstractAimsWe investigated N471D WASH complex subunit strumpellin (Washc5) knock‐in andWashc5knock‐out mice as models for hereditary spastic paraplegia type 8 (SPG8).MethodsWe generated heterozygous and homozygous N471DWashc5knock‐in mice and subjected them to a comprehensive clinical, morphological and laboratory parameter screen, and gait analyses. Brain tissue was used for proteomic analysis. Furthermore, we generated heterozygousWashc5knock‐out mice. WASH complex subunit strumpellin expression was determined by qPCR and immunoblotting.ResultsHomozygous N471DWashc5knock‐in mice showed mild dilated cardiomyopathy, decreased acoustic startle reactivity, thinner eye lenses, increased alkaline phosphatase and potassium levels and increased white blood cell counts. Gait analyses revealed multiple aberrations indicative of locomotor instability. Similarly, the clinical chemistry, haematology and gait parameters of heterozygous mice also deviated from the values expected for healthy animals, albeit to a lesser extent. Proteomic analysis of brain tissue depicted consistent upregulation of BPTF and downregulation of KLHL11 in heterozygous and homozygous knock‐in mice. WASHC5‐related protein interaction partners and complexes showed no change in abundancies. HeterozygousWashc5knock‐out mice showing normal WASHC5 levels could not be bred to homozygosity.ConclusionsWhile biallelic ablation ofWashc5was prenatally lethal, expression of N471D mutated WASHC5 led to several mild clinical and laboratory parameter abnormalities, but not to a typical SPG8 phenotype. The consistent upregulation of BPTF and downregulation of KLHL11 suggest mechanistic links between the expression of N471D mutated WASHC5 and the roles of both proteins in neurodegeneration and protein quality control, respectively.