Rab6 is increased in Alzheimer's disease brain and correlates with endoplasmic reticulum stress

Alzheimer's disease (AD) is characterized by deposits of aggregated proteins. Accumulation of aggregation-prone proteins activates protein quality control mechanisms, such as the unfolded protein response (UPR) in the endoplasmic reticulum (ER). We previously reported upregulation of the UPR marker BiP in AD brain. In this study, we investigated the small GTPase Rab6, which is involved in retrograde Golgi-ER trafficking and may function as a post-ER quality control system. Using immunohistochemistry and semiquantitative Western blotting, the expression of Rab6 was analysed in hippocampus, entorhinal and temporal cortex of 10 AD patients and six nondemented control subjects. Rab6 is upregulated in AD temporal cortex from Braak stage 3/4, the same stage that UPR activation is found. We observe increased neuronal Rab6 immunoreactivity in all brain areas examined. Although some neurones show colocalization of immunoreactivity for Rab6 and hyperphosphorylated tau, strong Rab6 staining does not colocalize with tangles. We find a highly significant correlation between the Rab6 and BiP levels. In vitro data show that Rab6 is not upregulated as a result of UPR activation or proteasome inhibition indicating an independent regulatory mechanism. Our data suggest that ER and post-ER protein quality control mechanisms are activated early in the pathology of AD.

Phenotype of Charcot-Marie-Tooth disease Type 2

OBJECTIVE

To investigate the clinical and electrophysiologic phenotype of Charcot-Marie-Tooth disease (CMT) Type 2 in a large number of affected families.

METHODS

We excluded CMT Type 1, hereditary neuropathy with liability to pressure palsies, and CMT due to Cx32 gene mutations by DNA analysis. We performed genetic analysis of the presently known CMT Type 2 genes.

RESULTS

Sixty-one persons from 18 families were affected. Ninety percent of patients were able to walk with or without the help of aids. Proximal leg muscle weakness was present in 13%. Asymmetrical features were present in 15%. Normal or brisk knee reflexes were present in 36%. Extensor plantar responses without associated spasticity occurred in 10 patients from eight families. Only three causative mutations were identified in the MFN2, BSCL2, and RAB7 genes. No mutations were found in the NEFL, HSPB1, HSPB8, GARS, DNM2, and GDAP1 genes.

CONCLUSIONS

At group level, the clinical phenotype of Charcot-Marie-Tooth disease (CMT) Type 2 is uniform, with symmetric, distal weakness, atrophy and sensory disturbances, more pronounced in the legs than in the arms, notwithstanding the genetic heterogeneity. Brisk reflexes, extensor plantar responses, and asymmetrical muscle involvement can be considered part of the CMT Type 2 phenotype. The causative gene mutation was found in only 17% of the families we studied.

Genetic variation in COMT and PRODH is associated with brain anatomy in patients with schizophrenia

Haploinsufficiency of 22q11 genes including catechol-O-methyltransferase (COMT) and proline dehydrogenase (PRODH) may result in structural and functional brain abnormalities and increased vulnerability to schizophrenia as observed in patients with microdeletions of 22q11. Thus, COMT and PRODH could be modifier genes for schizophrenia. We examined association of polymorphisms in COMT and PRODH with brain anatomy in young patients with schizophrenia and schizoaffective disorder. We acquired structural magnetic resonance imaging data from 51 male patients and genotyped two single nucleotide polymorphisms (SNPs) in the COMT gene and three in the PRODH gene. Statistical Parametric Mapping software and optimized voxel-based morphometry were used to determine regional gray matter (GM) and white matter (WM) density differences, and total GM and WM volume differences between genotype groups. Two nonsynonymous SNPs in the PRODH gene were associated with bilateral frontal WM density reductions and an SNP in the P2 promoter region of COMT (rs2097603) was associated with GM increase in the right superior temporal gyrus. Furthermore, we found evidence for COMT and PRODH epistasis: in patients with a COMT Val allele (rs4680) and with one or two mutated PRODH alleles, we observed increased WM density in the left inferior frontal lobe. Our results suggest that genetic variation in COMT and PRODH has significant effects on brain regions known to be affected in schizophrenia. Further research is needed to investigate the role of 22q11 genes on brain structure and function and their role in vulnerability for schizophrenia.

Results from an in vitro and a clinical/pharmacological phase I study with the combination irinotecan and sorafenib

PURPOSE

This single-centre, open-label, phase I dose-escalation study was performed to investigate the safety, pharmacokinetics (PK) and efficacy of sorafenib, a multi-kinase inhibitor, combined with irinotecan, a cytotoxic agent, in patients with advanced, refractory solid tumours.

PATIENTS AND METHODS

In an initial dose-escalation phase, patients received irinotecan 125 mg/m(2) and sorafenib 100, 200 and 400 mg twice daily (bid) (cohorts 1-3). In an extended phase, colorectal cancer (CRC) patients received fixed-dose irinotecan 140 mg and sorafenib 400 mg bid (cohort 4).

RESULTS

Thirty-four patients were treated: 20 in the dose-escalation phase (common tumour types: CRC [45%], ovarian [5%], pancreatic [5%]) and 14 patients in the CRC extension. Frequent drug-related adverse events were gastrointestinal symptoms, dermatological reactions and constitutional symptoms. The maximum tolerated dose was not reached. Generally, concomitant administration of irinotecan had no impact on the PK of sorafenib. Sorafenib 100 or 200 mg bid had no impact on the PK of irinotecan or its metabolite SN38. In contrast, sorafenib 400 mg bid significantly increased irinotecan and SN38 exposures; however, this was not associated with increased toxicities. Stable disease was achieved in 12/20 (60%) evaluable patients in cohorts 1-3, and 10/13 (77%) evaluable patients in cohort 4. A further patient from cohort 4 had a partial response of >200 days. The increase of SN38 exposure might be due to inhibition of formation of the SN38 glucuronide by sorafenib. In vitro, sorafenib strongly inhibited SN38 glucuronidation in human liver microsomes as indicated by a K(i) value of 2.7 micromol/l.

CONCLUSION

Sorafenib 400 mg bid can be combined with irinotecan 125 mg/m(2) or 140 mg for the treatment of patients with advanced, refractory solid tumours, although monitoring for toxicity is recommended.

Distal myoclonus and late onset in a large Dutch family with myoclonus-dystonia

We report a large myoclonus-dystonia (M-D) pedigree with a two-base pair deletion in Exon 5 of the epsilon-sarcoglycan gene. Three individuals had onset after age 40 years. Distal myoclonus of the arms was present in all 20 symptomatic mutation carriers. These findings expand the known phenotype of M-D and require revision of the current diagnostic criteria. Five of 14 asymptomatic mutation carriers who inherited the mutation from their mother showed minimal axial dystonia, arguing against a maternal imprinting mechanism.

Charcot-Marie-Tooth disease due to a de novo mutation of the RAB7 gene

We report a 32-year-old patient with Charcot-Marie-Tooth (CMT2B) including foot ulcerations. Genetic analysis identified a de novo mutation in the small GTP-ase late endosomal RAB7 gene, consisting of a c.471G>C, p.Lys157Asn missense mutation. This observation strongly supports the hypothesis that RAB7 mutations are responsible for CMT2B.

Always Around, Never the Same: Pathways of Amyloid Beta Induced Neurodegeneration Throughout the Pathogenic Cascade of Alzheimers Disease

There is an increasing amount of evidence showing the importance of intermediate aggregation species of amyloid beta (Abeta) in the pathogenic cascade of Alzheimer's disease (AD). Different Abeta assembly forms may mediate diverse toxic effects at different stages of the disease. Mouse models for AD suggest that intraneuronal accumulation of Abeta oligomers might be involved in AD pathogenesis at a very early stage of the disease. The detrimental effect of oligomeric Abeta on synaptic efficacy is suggested to be an early event in the pathogenic cascade. Also early neuronal responses as activation of the unfolded protein response are processes likely to be associated with the increased occurrence of oligomeric or low fibrillar Abeta in AD pathology. In later stages of AD pathology, the fibrillarity of Abeta increases, concomitantly with a neuroinflammatory response, followed by tau related neurofibrillary changes in end stage pathology. We will review recent findings in in vitro cell models, in vivo mouse models, and post mortem AD brain tissue in view of the effects of different Abeta peptide species on neurodegeneration during AD pathogenesis. Insight into the role of different Abeta species during AD pathogenesis is essential for the development of disease modifying drugs and therapeutical strategies.

Late onset axonal Charcot-Marie-Tooth phenotype caused by a novel myelin protein zero mutation

A late onset axonal Charcot-Marie-Tooth phenotype is described, resulting from a novel mutation in the myelin protein zero (MPZ) gene. Comparative computer modelling of the three dimensional structure of the MPZ protein predicts that this mutation does not cause a significant structural change. The primary axonal disease process in these patients points to a function of MPZ in maintenance of the myelinated axons, apart from securing stability of the myelin layer.

Phenotype-genotype correlation in Dutch patients with myoclonus-dystonia

The epsilon-sarcoglycan (SGCE) gene is an important cause of myoclonus-dystonia (M-D), although the majority of cases with an M-D phenotype test negative. Seven of 31 patients with the M-D phenotype carried a mutation in the SGCE gene. Positive family history and truncal myoclonus were independent prognostic factors. Early disease onset, onset with both myoclonus and dystonia, and axial dystonia were detected significantly more often in the mutation carriers.

Lack of association between VEGF polymorphisms and ALS in a Dutch population

Sequence alterations in the promoter region of the vascular endothelial growth factor (VEGF) gene have been implicated in increasing the risk of developing ALS. VEGF promoter haplotypes were determined in 373 patients with sporadic ALS and 615 matched healthy controls in The Netherlands. No significant association between the previously reported at-risk haplotypes and ALS was found. Pooling our results with the previously studied population still showed a significant association with the AAG haplotype.

The unfolded protein response is activated in Alzheimer's disease

Alzheimer's disease (AD) is, at the neuropathological level, characterized by the accumulation and aggregation of misfolded proteins. The presence of misfolded proteins in the endoplasmic reticulum (ER) triggers a cellular stress response called the unfolded protein response (UPR) that may protect the cell against the toxic buildup of misfolded proteins. In this study we investigated the activation of the UPR in AD. Protein levels of BiP/GRP78, a molecular chaperone which is up-regulated during the UPR, was found to be increased in AD temporal cortex and hippocampus as determined by Western blot analysis. At the immunohistochemical level intensified staining of BiP/GRP78 was observed in AD, which did not co-localize with AT8-positive neurofibrillary tangles. In addition, we performed immunohistochemistry for phosphorylated (activated) pancreatic ER kinase (p-PERK), an ER kinase which is activated during the UPR. p-PERK was observed in neurons in AD patients, but not in non-demented control cases and did not co-localize with AT8-positive tangles. Overall, these data show that the UPR is activated in AD, and the increased occurrence of BiP/GRP78 and p-PERK in cytologically normal-appearing neurons suggest a role for the UPR early in AD neurodegeneration. Although the initial participation of the UPR in AD pathogenesis might be neuroprotective, sustained activation of the UPR in AD might initiate or mediate neurodegeneration.

[From gene to disease; Charcot-Marie-Tooth disease or the hereditary motor and sensory neuropathies]

Charcot-Marie-Tooth disease is a clinically and genetically heterogeneous group of inherited neuropathies. The common clinical symptoms include distal muscle weakness, wasting and impaired distal sensation, more in the legs than in the arms, and reduced or absent reflexes. Moreover, foot and hand deformities are often encountered. A distinction between a primarily demyelinating or axonal neuropathy is often possible by means of nerve conduction studies. The major groups of inheritance are the autosomal dominant CMT1 (demyelinating), CMT2 (axonal) and the X-linked type (CMTX), but there are also autosomal recessive demyelinating (CMT4) and axonal (AR-CMT2) forms. The number of genes and loci is steadily increasing, with genes encoding proteins involved in myelin maintenance and axonal function, but also with genes encoding proteins, the function of which in peripheral nerve maintenance is notyet clear. Despite the increase in the number of known genes, especially for CMT2, there are many patients in whom no mutation can yet be found.

[From gene to disease: amyotrophic lateral sclerosis]

Amyotrophic lateral sclerosis is a progressive neurological disorder. It is characterised by selective motor-neuron degeneration in the cortex, brainstem, and spinal cord. Consequently, patients suffer from muscle weakness and usually die within 3-5 years after diagnosis from respiratory insufficiency. About 5-10% of the patients have a family history of ALS, the remaining are classified as sporadic ALS. There is only limited information about genetic susceptibility factors in sporadic ALS. Some patients with familial ALS have mutations in the gene encoding for copper/zinc superoxide dismutase, a protein involved in scavenging superoxide radicals. This results in a toxic gain of function. Mutations in the gene coding for alsin, ALS2, have been shown to be responsible for an autosomal recessive form of juvenile ALS.

Plasminogen Activator Inhibitor-1 4G Allele in the 4G/5G Promoter Polymorphism Increases the Occurrence of Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND AND PURPOSE

In several acute life-threatening diseases, the 4G-allele in the 4G/5G-promotor polymorphism in the plasminogen activator inhibitor-1 (PAI-1) gene is associated with higher PAI-1 levels and increased poor outcome, probably by promoting the formation of microthrombi. The aim of the present study was to investigate whether the PAI-1 4G/5G polymorphism is associated with the occurrence of cerebral ischemia, rebleeding, and other events, and clinical outcome after aneurysmal subarachnoid hemorrhage.

METHODS

DNA was collected and analyzed in 126 patients with aneurysmal subarachnoid hemorrhage admitted to the Academic Medical Centre Amsterdam and University Medical Centre Utrecht in the Netherlands. All episodes of deterioration were classified according to predefined criteria. Causes of poor outcome and functional outcome were assessed 3 months after the initial bleeding according to the 5-point Glasgow Outcome Scale (GOS).

RESULTS

Secondary ischemia occurred more often in patients with the 4G genotype than in patients homozygous for the 5G allele (RR: 3.3; 95% CI: 1.1 to 10.0). No significant differences were found between the groups for rebleeding or other events. Patients with the 4G genotype tended to have a higher risk for poor outcome than patients with the 5G/5G genotype (RR 1.2; 95% CI 0.7 to 2.2).

CONCLUSIONS

The 4G allele in the PAI-1 gene increases the risk for cerebral ischemia after aneurysmal subarachnoid hemorrhage (SAH) and probably also the risk for poor outcome. After early aneurysm occlusion, treatment aimed at enhancing fibrinolysis might be effective to prevent and treat cerebral ischemia in patients with aneurysmal SAH.

Hereditary motor and sensory neuropathy (HMSN) IA, developmental delay and autism related disorder in a boy with duplication (17)(p11.2p12)

We present a 6-year-old boy with moderate developmental delay, gait disturbance, autism related disorder and mild dysmorphic features. He was seen for evaluation of his retardation since the age of 2.8 years. At first sight, a cytogenetic analysis showed a normal 46,XY karyotype. Neurological examination at the age of 5.5 years revealed a motor and sensory polyneuropathy. A quantitative Southern blot with probes PMP22 and VAW409 specific for Charcot-Marie-Tooth type 1 (CMT1) disclosed a duplication which confirmed the diagnosis HMSN Ia. Subsequently, GTG banded metaphases were re-evaluated and a small duplication 17p was seen on retrospect. Additional FISH with probe LSISMS (Vysis) specific for the Smith-Magenis region at 17p11.2 again showed a duplication. Both parents had a normal karyotype and the duplication test for CMT1 showed normal results for both of them. The boy had a de novo 46,XY,dup(17)(p11.2p12) karyotype. The present observation confirms previous findings of mild psychomotor delay, neurobehavioural features and minor craniofacial anomalies as the major phenotypic features of dup(17)(p11.2) and dup(17)(p11.2p12); in cases of duplications comprising the PMP22 locus HMSN1 is associated. A recognizable facial phenotype emerges characterized by a broad forehead, hypertelorism, downslant of palpebral fissures, smooth philtrum, thin upper lip and ear anomalies.

Killing cancer by targeting genes that cancer cells have lost: allele-specific inhibition, a novel approach to the treatment of genetic disorders

Oligonucleotide-based drugs are now rapidly establishing themselves as an important tool in both research and treatment of genetic disorders. In the past many problems were encountered in using antisense oligonucleotides. Our expanding knowledge and new oligonucleotide chemistries are giving us the chance to treat serious genetic disorders such as cancer in novel, elegant and effective ways not previously possible. In addition, recent knowledge about RNA interference may add to these new approaches for disease treatment with oligonucleotide-based drugs. In this review we discuss one such novel therapeutic strategy against cancer called allele-specific inhibition (ASI). ASI is an approach where cancer cells are attacked at one of the few widely occurring and consistently weak points: the loss of large segments of DNA. Oligonucleotide-based drugs may provide the required selectivity for this therapeutic approach.

Two amino-acid substitutions in the myelin protein zero gene of a case of Charcot-Marie-Tooth disease associated with light-near dissociation

Charcot-Marie-Tooth disease caused by mutations of the myelin protein zero gene demonstrates considerable phenotypical variability. We describe a 45-year-old female with a peripheral neuropathy with demyelinating and axonal features, pes cavus and pupillary light-near dissociation. She was heterozygous for two mutations in the myelin protein zero gene (His81Tyr and Val113Phe), both present on the same allele. Our patient shows a less severe phenotype than previously described patients with a His81Arg mutation. Multiple mutations in the myelin protein zero gene, as well as Charcot-Marie-Tooth with pupillary abnormalities have previously been described in rare instances. However, concurrent occurrence of both phenomena is a novel finding.