Frequency of a tau genotype in amyotrophic lateral sclerosis

Parkinson-ALS with a novel MAPT variant

The mutations on microtubule associated protein tau (MAPT) gene manifest clinically with behavioural frontotemporal dementia (FTD), parkinsonism, such as progressive supranuclear palsy and corticobasal degeneration, and rarely with amyotrophic lateral sclerosis (ALS). FTD-parkinsonism and FTD-ALS are clinical overlaps included in the spectrum of MAPT mutation's phenotypes. The mutations on MAPT gene cause the dysfunction of tau protein determining its accumulation in neurofibrillary tangles. Recent data describe frequently the co-occurrence of the aggregation of tau protein and α-synuclein in patients with parkinsonism and Parkinson disease (PD), suggesting an interaction of the two proteins in determining neurodegenerative process. The sporadic description of PD-ALS clinical complex, known as Brait-Fahn-Schwarz disease, supports the hypothesis of common neuropathological pathways between different disorders. Here we report the case of a 54-year-old Italian woman with idiopathic PD later complicated by ALS carrying a novel MAPT variant (Pro494Leu). The variant is characterized by an amino acid substitution and is classified as damaging for MAPT functions. The case supports the hypothesis of tau dysfunction as the basis of multiple neurodegenerative disorders.

Knockdown of genes involved in axonal transport enhances the toxicity of human neuromuscular disease-linked MATR3 mutations in Drosophila

Mutations in the nuclear matrix protein Matrin 3 (MATR3) have been identified in amyotrophic lateral sclerosis and myopathy. To investigate the mechanisms underlying MATR3 mutations in neuromuscular diseases and efficiently screen for modifiers of MATR3 toxicity, we generated transgenic MATR3 flies. Our findings indicate that expression of wild-type or mutant MATR3 in motor neurons reduces climbing ability and lifespan of flies, while their expression in indirect flight muscles (IFM) results in abnormal wing positioning and muscle degeneration. In both motor neurons and IFM, mutant MATR3 expression results in more severe phenotypes than wild-type MATR3, demonstrating that the disease-linked mutations confer pathogenicity. We conducted a targeted candidate screen for modifiers of the MATR3 abnormal wing phenotype and identified multiple enhancers involved in axonal transport. Knockdown of these genes enhanced protein levels and insolubility of mutant MATR3. These results suggest that accumulation of mutant MATR3 contributes to toxicity and implicate axonal transport dysfunction in disease pathogenesis.

Role of MAPT in Pure Motor Neuron Disease: Report of a Recurrent Mutation in Italian Patients

The aim of our study was to evaluate the role of mutations in the MAPT gene in patients with pure amyotrophic lateral sclerosis (ALS). A cohort of 120 ALS patients, both sporadic and familial, without cognitive impairment was analyzed by next-generation sequencing with a multiple-gene panel comprising 23 genes, including MAPT, known to be associated with ALS and frontotemporal dementia. The presence of the C9orf72 expansion was also investigated. Twelve patients had mutations in the SOD1, TARDBP, MATR3, and FUS genes, while 10 patients carried the C9orf72 expansion. One female patient was found to carry the D348G mutation in MAPT, previously reported in an Italian family with lower motor neuron disease. Our patient presented both upper and lower motor neuron signs, early development of dyspnea, resting and kinetic tremor, and a slow disease course (> 11 years). The present case further broadens the clinical phenotype associated with MAPT mutations and suggests that, although rarely, MAPT mutations can cause ALS and, therefore, should be analyzed in ALS patients, especially in those with early breathing difficulties and long-lasting disease.

Intrafamilial phenotypic heterogeneity in a Taiwanese family with a MAPT p.R5H mutation: a case report and literature review

Background

Frontotemporal degeneration (FTD) is a clinically and genetically heterogeneous neurodegenerative disorder characterized by deficits in executive function that frequently overlaps with parkinsonism and motor neuron disorders. Several genes have been identified to cause autosomal dominant forms of FTD, including the gene coding for the protein associated with microtubule tau (MAPT). While most reported pathogenic mutations in MAPT occur in exons 9–13, few families have been reported with mutations outside of this region. Herein, we report a first Taiwanese family having the exon 1 p.Arg5His mutation in MAPT with intrafamilial phenotype heterogeneity.

Case presentation

A 63-year-old man presented with progressive non-fluent speech and impaired memory for 3 years. He then developed apraxia, myoclonus and parkinsonism feature at his right hand. Extensive neurologic and neurocognitive examination lead to a diagnosis of FTD mixed with corticobasal syndrome. Magnetic resonance imaging revealed asymmetric atrophy in the left frontal and temporal lobes and single-photon emission computed tomography indicated decreased metabolism in the same areas as well as the left basal ganglia. The patient’s mother had been diagnosed with amyotrophic lateral sclerosis (ALS) at the age of 60 and was deceased 10 years later due to respiratory failure. The patient’s younger sister had persistent depressive disorder in her early forties and did not have any prominent cognitive or motor dysfunctions. We performed genetic analysis applying a targeted next generation sequencing (NGS) panel covering MAPT, GRN, VCP, FUS, CHMP2B, and TARDBP on the proband, followed by Sanger sequencing of candidate genes in eight family members. Hexanucleotide repeat expansion of C9Orf72 was determined by repeat-primed PCR. We identified a missense mutation in exon 1 of MAPT gene, c.14G > A (p.R5H), which was previously reported in only two Japanese patients in a literature review. This substitution co-segregated with the disease phenotypes in the family.

Conclusions

This is the first report of the occurrence of the MAPT p.R5H mutation in the Taiwanese population. Our findings extend the current knowledge of phenotypic heterogeneity among family members carrying the MAPT p.R5H mutation.

MAPT as a predisposing gene for sporadic amyotrophic lateral sclerosis in the Chinese Han population

A previous study of European Caucasian patients with sporadic amyotrophic lateral sclerosis demonstrated that a polymorphism in the microtubule-associated protein Tau (MAPT) gene was significantly associated with sporadic amyotrophic lateral sclerosis pathogenesis. Here, we tested this association in 107 sporadic amyotrophic lateral sclerosis patients and 100 healthy controls from the Chinese Han population. We screened the mutation-susceptible regions of MAPT - the 3' and 5' untranslated regions as well as introns 9, 10, 11, and 12 - by direct sequencing, and identified 33 genetic variations. Two of these, 105788 A > G in intron 9 and 123972 T > A in intron 11, were not present in the control group. The age of onset in patients with the 105788 A > G and/or the 123972 T > A variant was younger than that in patients without either genetic variation. Moreover, the pa-tients with a genetic variation were more prone to bulbar palsy and breathing difficulties than those with the wild-type genotype. This led to a shorter survival period in patients with a MAPT genetic variant. Our study suggests that the MAPT gene is a potential risk gene for sporadic amyotrophic lateral sclerosis in the Chinese Han population.

Identification of Tau and SOD1 gene mutation in a small Chinese Han pedigree of adult amyotrophic lateral sclerosis

We report the clinical profile, and a brief investigation of SOD1 and Tau gene mutation from a small Chinese Han pedigree of adults with amyotrophic lateral sclerosis (ALS), which consisted of 32 familial members with 6 affected individuals spanning five generations, and presenting autosomal dominant genetic mode. The mean age of onset was 36.6 ± 15.9 years, and disease duration was 6 months to more than 5 years, the average survival was 16.1 ± 8.2 months. There were 5 patients with an early disease onset, rapid progressive course and short survival, and 1 patient with late onset, slow progressive course and long survival in the kindred. ALS patients began to suffer with weakness and muscle atrophy in one side of a lower extremity, which then spread to the upper extremity, the opposite side and bulbar muscles. All patients had spinal onset type. Muscle stretch reflexes were absent or weak in the upper limbs and accentuation in the lower limbs; pathological signs in the lower limbs were positive. Electromyography disclosed ongoing denervation muscle potentials in the four extremities. Brain and spinal MRI did not show any abnormal signal. A 5 exons mutation of SOD1 in all affected individuals was identified using SSCP. Polymorphisms of partial risk regions in 3',5' UTR, and in introns 9, 10, 11, 12 of the Tau gene in the affected and normal family members and in 70 healthy controls were examined by DNA sequencing. Routine exons mutation of SOD1 was not detected, but one single nucleotide polymorphism of A to G at 138278 at 3' UTR of the Tau gene was shown to significantly over-express in fALS familial members.

Molecular motor proteins and amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder affecting motor neurons in the brain, brainstem and spinal cord, which is characterized by motor dysfunction, muscle dystrophy and progressive paralysis. Both inherited and sporadic forms of ALS share common pathological features, however, the initial trigger of neurodegeneration remains unknown. Motor neurons are uniquely targeted by ubiquitously expressed proteins in ALS but the reason for this selectively vulnerability is unclear. However motor neurons have unique characteristics such as very long axons, large cell bodies and high energetic metabolism, therefore placing high demands on cellular transport processes. Defects in cellular trafficking are now widely reported in ALS, including dysfunction to the molecular motors dynein and kinesin. Abnormalities to dynein in particular are linked to ALS, and defects in dynein-mediated axonal transport processes have been reported as one of the earliest pathologies in transgenic SOD1 mice. Furthermore, dynein is very highly expressed in neurons and neurons are particularly sensitive to dynein dysfunction. Hence, unravelling cellular transport processes mediated by molecular motor proteins may help shed light on motor neuron loss in ALS.

Tau levels do not influence human ALS or motor neuron degeneration in the SOD1G93A mouse

BACKGROUND

The microtubule-associated protein tau is thought to play a pivotal role in neurodegeneration. Mutations in the tau coding gene MAPT are a cause of frontotemporal dementia, and the H1/H1 genotype of MAPT, giving rise to higher tau expression levels, is associated with progressive supranuclear palsy, corticobasal degeneration, and Parkinson disease (PD). Furthermore, tau hyperphosphorylation and aggregation is a hallmark of Alzheimer disease (AD), and reducing endogenous tau has been reported to ameliorate cognitive impairment in a mouse model for AD. Tau hyperphosphorylation and aggregation have also been described in amyotrophic lateral sclerosis (ALS), both in human patients and in the mutant SOD1 mouse model for this disease. However, the precise role of tau in motor neuron degeneration remains uncertain.

METHODS

The possible association between ALS and the MAPT H1/H2 polymorphism was studied in 3,540 patients with ALS and 8,753 controls. Furthermore, the role of tau in the SOD1(G93A) mouse model for ALS was studied by deleting Mapt in this model.

RESULTS

The MAPT genotype of the H1/H2 polymorphism did not influence ALS susceptibility (odds ratio = 1.08 [95% confidence interval 0.99-1.18], p = 0.08) and did not affect the clinical phenotype. Lowering tau levels in the SOD1(G93A) mouse failed to delay disease onset (p = 0.302) or to increase survival (p = 0.557).

CONCLUSION

These findings suggest that the H1/H2 polymorphism in MAPT is not associated with human amyotrophic lateral sclerosis, and that lowering tau levels in the mutant SOD1 mouse does not affect the motor neuron degeneration in these animals.