Anne-Dorte Sperfeld

Point mutations of the p150 subunit of dynactin (DCTN1) gene in ALS

The authors report mutation screening of the p150 subunit of dynactin (DCTN1) and the cytoplasmic dynein heavy chain (DNCHC1) genes in 250 patients with ALS and 150 unrelated control subjects. Heterozygous missense mutations of the DCTN1 gene were detected in one apparently sporadic case of ALS (T1249I), one individual with familial ALS (M571T), two patients with familial ALS, and two unaffected relatives in the same kindred (R785W). The allelic variants of the DCTN1 gene may represent a previously unknown genomic risk factor for ALS.

Heterozygous R1101K mutation of the DCTN1 gene in a family with ALS and FTD.

A heterozygous R1101K mutation of the p150 subunit of dynactin (DCTN1) is reported in a family with amyotrophic lateral sclerosis (ALS) and co‐occurrence of frontotemporal dementia (FTD). Two members of our kindred were affected with motor neuron disease and two with dementia in an autosomal dominant pattern of inheritance. We excluded the involvement of the ALS and FTD‐linked genes for copper/zinc superoxide dismutase (SOD1) and tau. The R1101K sequence alteration of the DCTN1 gene may predispose subjects to ALS and FTD. Ann Neurol 2005;58:777–780

Two German Kindreds With Familial Amyotrophic Lateral Sclerosis Due to TARDBP Mutations

BACKGROUND Abnormal neuronal inclusions composed of the transactivation response DNA-binding protein 43 (TDP-43) are characteristic neuropathologic lesions in sporadic and familial forms of amyotrophic lateral sclerosis (ALS). This makes TARDBP, the gene encoding for TDP-43, a candidate for genetic screening in ALS. OBJECTIVES To investigate the presence and frequency of TARDBP mutations in ALS. DESIGN Genetic analysis. SETTING Academic research. PARTICIPANTS One hundred thirty-four patients with sporadic ALS, 31 patients with familial non-superoxide dismutase 1 gene (non-SOD1) (OMIM 147450) ALS, and 400 healthy control subjects. MAIN OUTCOME MEASURES We identified 2 missense mutations (G348C and the novel N352S) in TARDBP in 2 small kindreds with a hereditary form of ALS with early spinal onset resulting in fatal respiratory insufficiency without clinical relevant bulbar symptoms or signs of cognitive impairment. RESULTS The mutations located in the C-terminus of TDP-43 were absent in 400 controls of white race/ethnicity. The novel identified N352S mutation is predicted to increase TDP-43 phosphorylation, while the G348C mutation might interfere with normal TDP-43 function by forming intermolecular disulfide bridges. CONCLUSIONS Mutations in TARDBP are a rare cause of familial non-SOD1 ALS. The identification of TARDBP mutations provides strong evidence for a direct link between TDP-43 dysfunction and neurodegeneration in ALS.

Global brain atrophy and corticospinal tract alterations in ALS, as investigated by voxel‐based morphometry of 3‐D MRI

In ALS, advanced magnetic resonance imaging (MRI) techniques are increasingly used to investigate the underlying pathology. In this study, the technique of voxel‐based morphometry (VBM) was applied to 3‐D MRI data in ALS patients to localize regional grey and white matter changes. Twenty‐two ALS patients (mean age 58±9 years) with clinically definite ALS by revised El Escorial criteria were studied. None of the patients had any signs of associated frontotemporal dementia. High‐resolution 3‐D MRI data sets of the whole brain, collected on a 1.5 T scanner, were analysed by statistical parametric mapping (SPM) and VBM in comparison to an age‐matched normal data base consisting of 22 healthy volunteers (mean age 59±11 years), for grey matter and white matter segments separately. Global brain atrophy was assessed by calculation of brain parenchymal fractions (BPF). In ALS patients, BPF were significantly reduced compared to controls (p = 0.0003), indicating global brain atrophy. Regional decreases of grey matter density were found in the ALS patients at corrected p<0.01 in the right‐hemispheric primary motor cortex (area of the highest Z‐score) and in the left medial frontal gyrus. Furthermore, regional white matter alterations were observed along the corticospinal tracts bilaterally and in multiple smaller areas including corpus callosum, cerebellum, frontal and occipital subcortical regions. Besides considerable global atrophy in ALS, the topography of ALS‐associated cerebral morphological changes could be mapped using VBM, in particular white matter signal changes along the bilateral corticospinal tracts, but also in extra‐motor areas. VBM might be a potential tool to visualize disease progression in future longitudinal studies.

High frequency of partial SPAST deletions in autosomal dominant hereditary spastic paraplegia.

Background: Hereditary spastic paraplegia (HSP) is a genetically heterogeneous neurodegenerative disease. The most frequent cause of autosomal dominant HSP is mutation of SPAST (SPG4 locus), but additional pedigrees remain mutation negative by conventional screening despite linkage to SPG4. Objective: To determine the frequency of genomic copy number aberrations of SPAST in autosomal dominant HSP. Methods: We developed and validated a multiplex ligation-dependent probe amplification assay targeting SPAST and SPG3A, another gene frequently involved in autosomal dominant HSP. In a multicenter study we subsequently investigated 65 index patients with autosomal dominant HSP, all of whom had previously been screened negative for SPAST mutations. Independent secondary samples, additional family members, and cDNA were analyzed to confirm positive findings. Results: Aberrant MLPA profiles were identified in 12 cases (18%). They exclusively affect SPAST, represent deletions, segregate with the disease, and are largely pedigree specific. Internal SPAST deletions entail expression of correspondingly shortened transcripts, which vary in stability. Age at onset in SPAST deletion carriers does not differ from that associated with other SPAST mutations. Conclusions: Partial SPAST deletions, but not SPAST amplifications and SPG3A copy number aberrations, represent an underestimated cause of autosomal dominant hereditary spastic paraplegia. Partial SPAST deletions are likely to act via haploinsufficiency.

Diagnosis and treatment of bulbar symptoms in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is the most common neurodegenerative disease of the motor system. Bulbar symptoms such as dysphagia and dysarthria are frequent features of ALS and can result in reductions in life expectancy and quality of life. These dysfunctions are assessed by clinical examination and by use of instrumented methods such as fiberendoscopic evaluation of swallowing and videofluoroscopy. Laryngospasm, another well-known complication of ALS, commonly comes to light during intubation and extubation procedures in patients undergoing surgery. Laryngeal and pharyngeal complications are treated by use of an array of measures, including body positioning, compensatory techniques, voice and breathing exercises, communication devices, dietary modifications, various safety strategies, and neuropsychological assistance. Meticulous monitoring of clinical symptoms and close cooperation within a multidisciplinary team (physicians, speech and language therapists, occupational therapists, dietitians, caregivers, the patients and their relatives) are vital.

Cardiac involvement in patients with Becker muscular dystrophy: new diagnostic and pathophysiological insights by a CMR approach

BackgroundBecker-Kiener muscular dystrophy (BMD) represents an X-linked genetic disease associated with myocardial involvement potentially resulting in dilated cardiomyopathy (DCM). Early diagnosis of cardiac involvement may permit earlier institution of heart failure treatment and extend life span in these patients. Both echocardiography and nuclear imaging methods are capable of detecting later stages of cardiac involvement characterised by wall motion abnormalities. Cardiovascular magnetic resonance (CMR) has the potential to detect cardiac involvement by depicting early scar formation that may appear before onset of wall motion abnormalities.MethodsIn a prospective two-center-study, 15 male patients with BMD (median age 37 years; range 11 years to 56 years) underwent comprehensive neurological and cardiac evaluations including physical examination, echocardiography and CMR. A 16-segment model was applied for evaluation of regional wall motion abnormalities (rWMA). The CMR study included late gadolinium enhancement (LGE) imaging with quantification of myocardial damage.ResultsAbnormal echocardiographic results were found in eight of 15 (53.3%) patients with all of them demonstrating reduced left ventricular ejection fraction (LVEF) and rWMA. CMR revealed abnormal findings in 12 of 15 (80.0%) patients (p = 0.04) with 10 (66.6%) having reduced LVEF (p = 0.16) and 9 (64.3%) demonstrating rWMA (p = 0.38). Myocardial damage as assessed by LGE-imaging was detected in 11 of 15 (73.3%) patients with a median myocardial damage extent of 13.0% (range 0 to 38.0%), an age-related increase and a typical subepicardial distribution pattern in the inferolateral wall. Ten patients (66.7%) were in need of medical heart failure therapy based on CMR results. However, only 4 patients (26.7%) were already taking medication based on clinical criteria (p = 0.009).ConclusionCardiac involvement in patients with BMD is underdiagnosed by echocardiographic methods resulting in undertreatment of heart failure. The degree and severity of cardiac involvement in this population is best characterised when state-of-the-art CMR methods are applied. Further studies need to demonstrate whether earlier diagnosis and institution of heart failure therapy will extend the life span of these patients.

Small-fiber neuropathy in patients with ALS

Objective: To investigate the involvement of the epidermal small sensory fibers in the neurodegenerative process in amyotrophic lateral sclerosis (ALS). Methods: In the present study, skin biopsies of 28 patients with ALS were obtained at an average of 34 months after disease onset by history. Protein gene product 9.5 (PGP9.5) immunohistochemistry findings were compared to 17 age-matched controls. The primary endpoint of the study was to evaluate the decrease in the density of small intraepidermal nerve fibers and to compare the prevalence of small-fiber neuropathy in patients with ALS and in controls. Results: We found a significant reduction in epidermal nerve fiber density in the distal calf of patients with ALS (4.8 ± 3.7 fibers/mm vs 12.2 ± 4.6 in age-matched controls, p < 0.0001). The extent of fiber loss was age-dependent. Also, the number of subjects with small-fiber neuropathy was significantly higher in the ALS group than in the controls (79% vs 12%). Correspondingly, mild sensory symptoms including diffuse dysesthesias, paresthesias, and hypesthesia were found in 7 patients. In 17 biopsies of patients with ALS, but only in 2 controls, we saw larger (>1.5 μm in diameter) focal swellings of epidermal axons resembling spheroids, suggesting trafficking defects. Conclusions: These results indicate that small, distal epidermal nerve fibers are involved in this disease, supporting the concept of distal axonopathy in ALS.

Four familial ALS pedigrees discordant for two SOD1 mutations : are all SOD1 mutations pathogenic?

Background 153 mutations in the Cu/Zn superoxide dismutase (SOD1) gene have been claimed to be associated with amyotrophic lateral sclerosis (ALS) in familial and sporadic ALS in an autosomal dominant or autosomal recessive pattern with complete or reduced penetrance. The authors now report four ALS pedigrees from Finland, France, Germany and Sweden with either the D90A or E100K SOD1 mutations in some but not all affected members. After re-collecting DNA, the non-segregation of the SOD1 mutations with disease was confirmed by three independent laboratories using different PCR primers: while some of the affected patients carry SOD1 mutations, other affected family members have two wildtype/normal SOD1 genes. In addition, some unaffected members within the same families are carriers of SOD1 gene mutations. To exclude other known genetic causes, the authors ruled out mutations within the genes coding for VAPB, ANG, TDP43, FUS and DCTN1 in affected individuals in the four pedigrees. Conclusions The authors find that the D90A and E100K SOD1 gene mutations found in some patients are not the exclusive cause of ALS in these pedigrees. Whether this is also the case for the other 151 SOD1 mutations reported in ALS pedigrees is unknown. The findings have consequences for genetic testing in clinical practice when diagnosing ALS and for genetic counselling in ALS. Some SOD1 mutations may be part of an oligo- or epigentic pattern of inheritance. Such a pattern of inheritance may model other oligo- or polygenetic traits responsible for other forms of ALS.

Accelerated aging phenotype in mice with conditional deficiency for mitochondrial superoxide dismutase in the connective tissue

The free radical theory of aging postulates that the production of mitochondrial reactive oxygen species is the major determinant of aging and lifespan. Its role in aging of the connective tissue has not yet been established, even though the incidence of aging‐related disorders in connective tissue‐rich organs is high, causing major disability in the elderly. We have now addressed this question experimentally by creating mice with conditional deficiency of the mitochondrial manganese superoxide dismutase in fibroblasts and other mesenchyme‐derived cells of connective tissues in all organs. Here, we have shown for the first time that the connective tissue‐specific lack of superoxide anion detoxification in the mitochondria results in reduced lifespan and premature onset of aging‐related phenotypes such as weight loss, skin atrophy, kyphosis (curvature of the spine), osteoporosis and muscle degeneration in mutant mice. Increase in p16INK4a, a robust in vivo marker for fibroblast aging, may contribute to the observed phenotype. This novel model is particularly suited to decipher the underlying mechanisms and to develop hopefully novel connective tissue‐specific anti‐aging strategies.