TDP-43 differentially propagates to induce antero- and retrograde degeneration in the corticospinal circuits in mouse focal ALS models.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by TDP-43 inclusions in the cortical and spinal motor neurons. It remains unknown whether and how pathogenic TDP-43 spreads across neural connections to progress degenerative processes in the cortico-spinal motor circuitry. Here we established novel mouse ALS models that initially induced mutant TDP-43 inclusions in specific neuronal or cell types in the motor circuits, and investigated whether TDP-43 and relevant pathological processes spread across neuronal or cellular connections. We first developed ALS models that primarily induced TDP-43 inclusions in the corticospinal neurons, spinal motor neurons, or forelimb skeletal muscle, by using adeno-associated virus (AAV) expressing mutant TDP-43. We found that TDP-43 induced in the corticospinal neurons was transported along the axons anterogradely and transferred to the oligodendrocytes along the corticospinal tract (CST), coinciding with mild axon degeneration. In contrast, TDP-43 introduced in the spinal motor neurons did not spread retrogradely to the cortical or spinal neurons; however, it induced an extreme loss of spinal motor neurons and subsequent degeneration of neighboring spinal neurons, suggesting a degenerative propagation in a retrograde manner in the spinal cord. The intraspinal degeneration further led to severe muscle atrophy. Finally, TDP-43 induced in the skeletal muscle did not propagate pathological events to spinal neurons retrogradely. Our data revealed that mutant TDP-43 spread across neuro-glial connections anterogradely in the corticospinal pathway, whereas it exhibited different retrograde degenerative properties in the spinal circuits. This suggests that pathogenic TDP-43 may induce distinct antero- and retrograde mechanisms of degeneration in the motor system in ALS.

Accuracy of a machine learning method based on structural and locational information from AlphaFold2 for predicting the pathogenicity of TARDBP and FUS gene variants in ALS.

BACKGROUND: In the sporadic form of amyotrophic lateral sclerosis (ALS), the pathogenicity of rare variants in the causative genes characterizing the familial form remains largely unknown. To predict the pathogenicity of such variants, in silico analysis is commonly used. In some ALS causative genes, the pathogenic variants are concentrated in specific regions, and the resulting alterations in protein structure are thought to significantly affect pathogenicity. However, existing methods have not taken this issue into account. To address this, we have developed a technique termed MOVA (method for evaluating the pathogenicity of missense variants using AlphaFold2), which applies positional information for structural variants predicted by AlphaFold2. Here we examined the utility of MOVA for analysis of several causative genes of ALS. METHODS: We analyzed variants of 12 ALS-related genes (TARDBP, FUS, SETX, TBK1, OPTN, SOD1, VCP, SQSTM1, ANG, UBQLN2, DCTN1, and CCNF) and classified them as pathogenic or neutral. For each gene, the features of the variants, consisting of their positions in the 3D structure predicted by AlphaFold2, pLDDT score, and BLOSUM62 were trained into a random forest and evaluated by the stratified fivefold cross validation method. We compared how accurately MOVA predicted mutant pathogenicity with other in silico prediction methods and evaluated the prediction accuracy at TARDBP and FUS hotspots. We also examined which of the MOVA features had the greatest impact on pathogenicity discrimination. RESULTS: MOVA yielded useful results (AUC ≥ 0.70) for TARDBP, FUS, SOD1, VCP, and UBQLN2 of 12 ALS causative genes. In addition, when comparing the prediction accuracy with other in silico prediction methods, MOVA obtained the best results among those compared for TARDBP, VCP, UBQLN2, and CCNF. MOVA demonstrated superior predictive accuracy for the pathogenicity of mutations at hotspots of TARDBP and FUS. Moreover, higher accuracy was achieved by combining MOVA with REVEL or CADD. Among the features of MOVA, the x, y, and z coordinates performed the best and were highly correlated with MOVA. CONCLUSIONS: MOVA is useful for predicting the virulence of rare variants in which they are concentrated at specific structural sites, and for use in combination with other prediction methods.

[ATTRv amyloidosis with early improvement demonstrated by the 6-minute walk test following Patisiran therapy: a case report].

We report the case of a 65-year-old man who gradually developed numbness in both hands, lower limb muscle weakness and atrophy, and orthostatic hypotension over two and a half years. These symptoms indicated hereditary ATTR amyloidosis (ATTRv amyloidosis), and the final diagnosis was established through proof of TTR gene mutation (V30M). We initiated patisiran therapy, and a continuous 6-minute walking test performed 3 weeks from the start of therapy demonstrated improvement in the walking distance. This is a single case report showing the improvement in the motor and sensory function on administration of patisiran monotherapy from an early stage.

[Molecular mechanism of amyotrophic lateral sclerosis (ALS) from the viewpoint of the formation and degeneration of transactive response DNA-binding protein 43†kDa (TDP-43) inclusions].

Sporadic amyotrophic lateral sclerosis (SALS) and many cases of familial ALS (FALS) demonstrate cytoplasmic transactive response DNA-binding protein 43 kDa (TDP-43)-positive inclusion bodies. Thus, TDP-43 plays a vital role in ALS pathogenesis. Functional analysis of the ALS causative genes advanced the elucidation of the mechanism associated with the formation and degradation of TDP-43 aggregates. Stress granules, which are non-membranous organelles, are attracting attention as sites of aggregate formation, with involvement of FUS and C9orf72. Concurrently, ALS causative genes related to the ubiquitin-proteasome and autophagy systems, which are aggregate degradation mechanisms, have also been reported. Therefore, therapeutic research based on the molecular pathology common to SALS and FALS has been advanced.

A case of central pontine and extrapontine myelinolysis after surgery for a pituitary tumor.

A 21-year-old woman underwent surgery for a pituitary tumor. On the 11th postoperative day, blood examination revealed severe hyponatremia, with a serum sodium level of 111 mEq/l, and two days later this increased rapidly to 137 mEq/l. On the 20th postoperative day, the patient developed dysarthria and gait disturbance. Head MRI on the 30th postoperative day demonstrated intense high-signal lesions in the pons and bilateral corpus striatum on FLAIR and DWI, and central pontine and extrapontine myelinolysis was diagnosed. The patient's symptoms improved gradually after rehabilitation and antispasticity treatment. It was suggested that the changes in serum sodium levels after pituitary surgery were due to impaired secretion of antidiuretic hormone due to degeneration of nerve terminals in the posterior pituitary. As pituitary surgery may trigger changes in serum sodium leading to myelinolysis, this possibility should always be borne in mind when treating such patients.

[Clinical course and serial brain MRI findings in a patient with Lissauer form of general paresis].

A 60-year-old man presented with progressive dementia and generalized convulsions. An initial MRI revealed a widespread high-intensity area with a mass effect in the right frontal and temporal lobes on T2-weighted images. Findings on digital subtraction angiography were normal. Serum and CSF tests showed high titers of antibodies to Treponema pallidum, which helped to distinguish neurosyphilis from glioma. He was initially treated with penicillin injection; however, it caused liver dysfunction and penicillin was switched to erythromycin. Even after antibiotic therapy for 2 months, his dementia did not improve. He underwent brain MRI four times during the treatment course, and they showed steady progression of brain atrophy in the right hemisphere. Taking these findings together, we diagnosed Lissauer form of general paresis. To the best of our knowledge, this is the first case of Lissauer form of paretic neurosyphilis, in which the progression of brain atrophy was clearly demonstrated on MRI.