Hereditary spastic paraplegia type 8: Neuropathological findings

N471D WASH complex subunit strumpellin knock-in mice display mild motor and cardiac abnormalities and BPTF and KLHL11 dysregulation in brain tissue

AIMS

We investigated N471D WASH complex subunit strumpellin (Washc5) knock-in and Washc5 knock-out mice as models for hereditary spastic paraplegia type 8 (SPG8).

METHODS

We generated heterozygous and homozygous N471D Washc5 knock-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 heterozygous Washc5 knock-out mice. WASH complex subunit strumpellin expression was determined by qPCR and immunoblotting.

RESULTS

Homozygous N471D Washc5 knock-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. Heterozygous Washc5 knock-out mice showing normal WASHC5 levels could not be bred to homozygosity.

CONCLUSIONS

While biallelic ablation of Washc5 was 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.

Familial multiple sclerosis patients have a shorter delay in diagnosis than sporadic cases

BACKGROUND

The diagnosis of multiple sclerosis (MS) is still complicated despite improvement in diagnostic guidelines. This means that time from first symptom to diagnosis in some cases is prolonged. Many aspects of MS aetiology are unknown, but the involvement of a genetic component is well established. This is also highlighted by the occurrence of familial MS cases, which represent 10-20% of all MS cases. We hypothesize that subsequent family members in a MS family, have a shorter time from onset of disease to diagnosis compared to sporadic MS cases. To investigate this, we have conducted a register study comparing time from onset to diagnosis in familial and sporadic MS cases.

METHODS

This is a nationwide register study based on information from the Danish Multiple Sclerosis Registry and the Danish Civil Registration System. We included familial (first-degree relatives) and sporadic MS cases and calculated time lag between onset and diagnosis of MS for sporadic MS cases and for1st, 2nd and 3rd family members within the MS families. Median test and Cox regression were the statistical methods used to compare the familial and sporadic groups.

RESULTS

We found that 2nd and 3rd affected family member had a significant shorter time from first symptom to diagnosis compared to sporadic MS cases (2nd family member: Hazard Ratio (HR): 1.12, CI: 1.03-1.21, p = 0.007 adjusted: HR: 0.95 p = 0.22, CI 0.89-1-03 and 3rd family member HR: 1.64 CI: 1.22-2.20, p = 0.001 adjusted model: HR: 1.70, p-value: 0.000, CI: 1.32-2.18). The same difference was not seen between 1st family members and sporadic cases (HR: 1.05, CI: 0.98-1.13, p = 0.15, adjusted: 0.98, p-value: 0.53, CI: 0.91-1.05). Estimated marginal mean delay in the four groups were 4.60 years (95% CI: 4.11-5.01) in1st family members, 4.23 years (3.71-4.75) in 2nd family members, 2.11 years (0.95-3.26) in 3rd family members and 4.99 years (4.99-4.99) in sporadic MS cases.

CONCLUSION

The 2nd and 3rd family members in MS families tend do get diagnosed faster than sporadic cases. This has implications in the diagnostic process of familial MS cases.