Gabriele Siciliano

Mutations in the Matrin 3 gene cause familial amyotrophic lateral sclerosis

MATR3 is an RNA- and DNA-binding protein that interacts with TDP-43, a disease protein linked to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. Using exome sequencing, we identified mutations in MATR3 in ALS kindreds. We also observed MATR3 pathology in ALS-affected spinal cords with and without MATR3 mutations. Our data provide more evidence supporting the role of aberrant RNA processing in motor neuron degeneration.

Causative and susceptibility genes for Alzheimer's disease: a review.

Alzheimers disease (AD) is the most common type of dementia in the elderly population. Three genes have been identified as responsible for the rare early-onset familial form of the disease: the amyloid precursor protein (APP) gene, the presenilin 1 (PSEN1) gene and the presenilin 2 (PSEN2) gene. Mutations in these genes, however, account for less than 5% of the total number of AD cases. The remaining 95% of AD patients are mostly sporadic late-onset cases, with a complex aetiology due to interactions between environmental conditions and genetic features of the individual. In this paper, we review the most important genes supposed to be involved in the pathogenesis of AD, known as susceptibility genes, in an attempt to provide a comprehensive picture of what is known about the genetic mechanisms underlying the onset and progression of AD. Hypotheses about the role of each gene in the pathogenic pathway are discussed, taking into account the functions and molecular features, if known, of the coded protein. A major susceptibility gene, the apolipoprotein E (APOE) gene, found to be associated with sporadic late-onset AD cases and the only one, whose role in AD has been confirmed in numerous studies, will be included in a specific chapter. As the results reported by association studies are conflicting, we conclude that a better understanding of the complex aetiology that underlies AD may be achieved likely through a multidisciplinary approach that combines clinical and neurophysiological characterization of AD subtypes and in vivo functional brain imaging studies with molecular investigations of genetic components.

APOE and Alzheimer disease: a major gene with semi-dominant inheritance

Apolipoprotein E (APOE) dependent lifetime risks (LTRs) for Alzheimer Disease (AD) are currently not accurately known and odds ratios alone are insufficient to assess these risks. We calculated AD LTR in 7351 cases and 10 132 controls from Caucasian ancestry using Rochester (USA) incidence data. At the age of 85 the LTR of AD without reference to APOE genotype was 11% in males and 14% in females. At the same age, this risk ranged from 51% for APOE44 male carriers to 60% for APOE44 female carriers, and from 23% for APOE34 male carriers to 30% for APOE34 female carriers, consistent with semi-dominant inheritance of a moderately penetrant gene. Using PAQUID (France) incidence data, estimates were globally similar except that at age 85 the LTRs reached 68 and 35% for APOE 44 and APOE 34 female carriers, respectively. These risks are more similar to those of major genes in Mendelian diseases, such as BRCA1 in breast cancer, than those of low-risk common alleles identified by recent GWAS in complex diseases. In addition, stratification of our data by age groups clearly demonstrates that APOE4 is a risk factor not only for late-onset but for early-onset AD as well. Together, these results urge a reappraisal of the impact of APOE in Alzheimer disease.

Cytochrome c oxidase and mitochondrial F1F0-ATPase (ATP synthase) activities in platelets and brain from patients with Alzheimer’s disease

Evidence suggests that mitochondrial dysfunction is prominent in Alzheimers disease (AD). A failure of one or more of the mitochondrial electron transport chain enzymes or of F(1)F(0)-ATPase (ATP synthase) could compromise brain energy stores, generate damaging reactive oxygen species (ROS), and lead to neuronal death. In the present study, cytochrome c oxidase (COX) and F(1)F(0)-ATPase activities of isolated mitochondria from platelets and postmortem motor cortex and hippocampus from AD patients and age-matched control subjects were assayed. Compared with controls, COX activity was decreased significantly in platelets (-30%, P < 0.01, n = 20) and hippocampus (-35 to -40%, P < 0.05, n = 6), but not in motor cortex from the AD patients. In contrast, in AD platelets and brain tissues, F(1)F(0)-ATP hydrolysis activity was not significantly changed. Moreover, the ATP synthesis rate was similar in mitochondria of platelets from AD patients and controls. These results demonstrate that COX but not F(1)F(0)-ATPase is a mitochondrial target in AD, in both a brain association area and in platelets. A reduced COX activity may make the tissue vulnerable to excitotoxicity or reduced oxygen availability.

Oxidative DNA damage in peripheral leukocytes of mild cognitive impairment and AD patients.

It is well established that oxidative stress plays a key role in the degenerative neuronal death and progression of Alzheimers disease (AD), although it is not clear if it is the primary triggering event in the pathogenesis of this disorder. Mild cognitive impairment (MCI) is a clinical condition between normal aging and AD, characterized by a memory deficit without loss of general cognitive and functional abilities. We performed this study by a comet assay analysis to evaluate the level of primary and oxidative DNA damage in two groups of MCI and AD patients, compared to healthy controls. Data showed a significantly higher level of primary DNA damage in leukocytes of AD and also of MCI patients compared to control individuals (average: 2.09+/-0.79 and 2.47+/-1.01, respectively for AD and MCI, versus 1.04+/-0.31 in controls). Moreover, the amount of oxidised DNA bases (both purines and pyrimidines) was significatively higher in the two groups of patients (AD and MCI) compared to controls. Our results give a further indication that oxidative stress, at least at the DNA level, is an earlier event in the pathogenesis of AD.

Executive dysfunction and avoidant personality trait in myotonic dystrophy type 1 (DM-1) and in proximal myotonic myopathy (PROMM/DM-2)

A previous study in proximal myotonic myopathy (PROMM/DM-2) and myotonic dystrophy type 1 (DM-1) using brain positron emission tomography demonstrated a reduced cerebral blood flow in the frontal and temporal regions associated with cognitive impairment. The objective was to investigate further cognitive and behavioural aspects in a new series of patients with DM-1 and PROMM/DM-2. Nineteen patients with genetically determined PROMM/DM-2 and 21 patients with moderately severe DM-1 underwent neuropsychological testing and neuropsychiatric interviews. DM-1 and PROMM/DM-2 patients had significantly lower scores on tests of frontal lobe function compared to controls. Neuropsychiatric interviews demonstrated an avoidant trait personality disorder in both patient groups. Brain single photon emission computed tomography showed frontal and parieto-occipital hypoperfusion. The results suggest that there is a specific cognitive and behavioural profile in PROMM/DM-2 and in DM-1, and that this profile is associated with hypoperfusion in frontal and parieto-occipital regions of the brain.

Mutations of FUS Gene in Sporadic Amyotrophic Lateral Sclerosis

Background Mutations in the FUS gene have recently been discovered to be a major cause of familial amyotrophic lateral sclerosis (FALS). Objective To determine the identity and frequency of FUS gene mutations in a large cohort of Italian patients enriched in sporadic cases (SALS). Methods Exons 5, 6, 14 and 15 of the FUS gene were screened for mutations in 1009 patients (45 FALS and 964 SALS). The genetic analysis was extended to the entire coding sequence of FUS in all the FALS and 293 of the SALS patients. Results Seven missense mutations (p.G191S, p.R216C, p.G225V, p.G230C, p.R234C, p.G507D and p.R521C) were identified in nine patients (seven SALS and two FALS), and none in 500 healthy Italian controls. All mutations are novel except for the p.R521C mutation identified in one SALS and one FALS case. Both patients showed a similar unusual presentation, with proximal, mostly symmetrical, upper limb weakness, with neck and axial involvement. With the exception of p.G507D and p.R521C, the mutations identified in SALS patients are all localised in the glycine-rich region encoded by exon 6. In addition, eight different in-frame deletions in two polyglycine motifs were detected, the frequency of which was not significantly different in patients and controls. Conclusions The results show that FUS missense mutations are present in 0.7% of Italian SALS cases, and confirm the previous mutational frequency reported in FALS (4.4%). An unusual proximal and axial clinical presentation seems to be associated with the presence of the p.R521C mutation.

A two-stage genome-wide association study of sporadic amyotrophic lateral sclerosis

The cause of sporadic amyotrophic lateral sclerosis (ALS) is largely unknown, but genetic factors are thought to play a significant role in determining susceptibility to motor neuron degeneration. To identify genetic variants altering risk of ALS, we undertook a two-stage genome-wide association study (GWAS): we followed our initial GWAS of 545 066 SNPs in 553 individuals with ALS and 2338 controls by testing the 7600 most associated SNPs from the first stage in three independent cohorts consisting of 2160 cases and 3008 controls. None of the SNPs selected for replication exceeded the Bonferroni threshold for significance. The two most significantly associated SNPs, rs2708909 and rs2708851 [odds ratio (OR) = 1.17 and 1.18, and P-values = 6.98 x 10(-7) and 1.16 x 10(-6)], were located on chromosome 7p13.3 within a 175 kb linkage disequilibrium block containing the SUNC1, HUS1 and C7orf57 genes. These associations did not achieve genome-wide significance in the original cohort and failed to replicate in an additional independent cohort of 989 US cases and 327 controls (OR = 1.18 and 1.19, P-values = 0.08 and 0.06, respectively). Thus, we chose to cautiously interpret our data as hypothesis-generating requiring additional confirmation, especially as all previously reported loci for ALS have failed to replicate successfully. Indeed, the three loci (FGGY, ITPR2 and DPP6) identified in previous GWAS of sporadic ALS were not significantly associated with disease in our study. Our findings suggest that ALS is more genetically and clinically heterogeneous than previously recognized. Genotype data from our study have been made available online to facilitate such future endeavors.

Phenotypic manifestations associated with CAG-repeat expansion in the androgen receptor gene in male patients and heterozygous females: a clinical and molecular study of 30 families

Spinal and bulbar muscular atrophy (Kennedy disease) is an adult form of X-linked motor neuron disease caused by the expansion of a polymorphic CAG-repeat sequence in the first exon of the androgen receptor gene. We studied clinical and molecular features of 36 patients and 19 heterozygous females. Phenotypic manifestations and disease severity broadly varied among our spinal and bulbar muscular atrophy patients. The size of CAG expansion significantly influences the age of disease onset, but neither clinical features nor disease severity. The majority of carrier women presented signs of chronic denervation at neurophysiological examination and, in three cases, low-amplitude sensory action potentials were recorded. Notably, a few women developed mild signs of bulbar motor neuron impairment later in life. The identification of a large number of patients by the use of the molecular test further supports the hypothesis that Kennedy disease had been previously underdiagnosed, probably because of the great variability of clinical presentation. Although an early diagnosis may not be crucial for treatment, given the lack of effective therapy, the molecular testing can be of great relevance for disease prognosis and genetic counseling.

Multi‐center assessment of the Total Neuropathy Score for chemotherapy‐induced peripheral neurotoxicity

Abstract  The aim of this multi‐center study was to assess with reduced versions of the Total Neuropathy Score (TNS), the severity of chemotherapy‐induced peripheral neurotoxicity (CIPN), and to compare the results with those obtained with common toxicity scales. An unselected population of 428 cancer patients was evaluated at 11 different centers using a composite (clinical + neurophysiological, TNSr) or clinical (TNSc) examination and with the National Cancer Institute – Common Toxicity Criteria (NCI‐CTC) 2.0 and Eastern Cooperative Oncology Group (ECOG) scores. A highly significant correlation was demonstrated between the TNSr and the NCI‐CTC 2.0 and ECOG scores; but the TNSr evaluation was more accurate in view of the more extended score range. Also, the simpler and faster TNSc (based only on the clinical neurological examination) allowed to grade accurately CIPN and correlated with the common toxicity scores. The correlation tended to be closer when the sensory items were considered, but also the TNSr motor items, which were not specifically investigated in any other previous study, significantly correlated with the results of the common toxicity scales. In conclusion, this study suggests that the TNSr is a reliable tool for accurately grading and reporting CIPN, with the additional and so far unique support of a formal comparison with known and widely used common toxicity scales. The TNSc is a valid alternative if neurophysiological examination is not feasible. The longer time needed to calculate the TNSr and TNSc in comparison to the ECOG or the NCI‐CTC 2.0 scales is offset by the more detailed knowledge of the CIPN characteristics.