Genetics of familial and sporadic amyotrophic lateral sclerosis

Diseases affecting motor neurons, such as amyotrophic lateral sclerosis (Lou Gerhig's disease), hereditary spastic paraplegia and spinal bulbar muscular atrophy (Kennedy's disease) are a heterogeneous group of chronic progressive diseases and are among the most puzzling yet untreatable illnesses. Over the last decade, identification of mutations in genes predisposing to these disorders has provided the means to better understand their pathogenesis. The discovery 13 years ago of SOD1 mutations linked to ALS, which account for less than 2% of total cases, had a major impact in the field. However, despite intensive research effort, the pathways leading to the specific motor neurons degeneration in the presence of SOD1 mutations have not been fully identified. This review provides an overview of the genetics of both familial and sporadic forms of ALS.     

Global Brain Gene Expression Analysis Links Glutamatergic and GABAergic Alterations to Suicide and Major Depression

Background

Most studies investigating the neurobiology of depression and suicide have focused on the serotonergic system. While it seems clear that serotonergic alterations play a role in the pathogenesis of these major public health problems, dysfunction in additional neurotransmitter systems and other molecular alterations may also be implicated. Microarray expression studies are excellent screening tools to generate hypotheses about additional molecular processes that may be at play. In this study we investigated brain regions that are known to be implicated in the neurobiology of suicide and major depression are likely to represent valid global molecular alterations.

Methodology/Principal Findings

We performed gene expression analysis using the HG-U133AB chipset in 17 cortical and subcortical brain regions from suicides with and without major depression and controls. Total mRNA for microarray analysis was obtained from 663 brain samples isolated from 39 male subjects, including 26 suicide cases and 13 controls diagnosed by means of psychological autopsies. Independent brain samples from 34 subjects and animal studies were used to control for the potential confounding effects of comorbidity with alcohol. Using a Gene Ontology analysis as our starting point, we identified molecular pathways that may be involved in depression and suicide, and performed follow-up analyses on these possible targets. Methodology included gene expression measures from microarrays, Gene Score Resampling for global ontological profiling, and semi-quantitative RT-PCR. We observed the highest number of suicide specific alterations in prefrontal cortical areas and hippocampus. Our results revealed alterations of synaptic neurotransmission and intracellular signaling. Among these, Glutamatergic (GLU) and GABAergic related genes were globally altered. Semi-quantitative RT-PCR results investigating expression of GLU and GABA receptor subunit genes were consistent with microarray data.

Conclusions/Significance

The observed results represent the first overview of global expression changes in brains of suicide victims with and without major depression and suggest a global brain alteration of GLU and GABA receptor subunit genes in these conditions.     

An overview of models of stomatal conductance at the leaf level

Stomata play a key role in plant adaptation to changing environmental conditions as they control both water losses and CO₂ uptake. Particularly, in the context of global change, simulations of the consequences of drought on crop plants are needed to design more efficient and water‐saving cropping systems. However, most of the models of stomatal conductance (g_s) developed at the leaf level link g_s to environmental factors or net photosynthesis (A_net), but do not include satisfactorily the effects of drought, impairing our capacity to simulate plant functioning in conditions of limited water supply. The objective of this review was to draw an up‐to‐date picture of the g_s models, from the empirical to the process‐based ones, along with their mechanistic or deterministic bases. It focuses on models capable to account for multiple environmental influences with emphasis on drought conditions. We examine how models that have been proposed for well‐watered conditions can be combined with those specifically designed to deal with drought conditions. Ideas for future improvements of g_s models are discussed: the issue of co‐regulation of g_s and A_net; the roles of CO₂, absissic acid and H₂O₂; and finally, how to better address the new challenges arising from the issue of global change.     

Evolution of xyloglucan-related genes in green plants

Background  

The cell shape and morphology of plant tissues are intimately related to structural modifications in the primary cell wall that are associated with key processes in the regulation of cell growth and differentiation. The primary cell wall is composed mainly of cellulose immersed in a matrix of hemicellulose, pectin, lignin and some structural proteins. Xyloglucan is a hemicellulose polysaccharide present in the cell walls of all land plants (Embryophyta) and is the main hemicellulose in non-graminaceous angiosperms.     

A regulated interaction with the UIM protein Eps15 implicates parkin in EGF receptor trafficking and PI(3)K-Akt signalling

Mutations in the parkin gene are responsible for a common familial form of Parkinson's disease. As parkin encodes an E3 ubiquitin ligase, defects in proteasome-mediated protein degradation are believed to have a central role in the pathogenesis of Parkinson's disease. Here, we report a novel role for parkin in a proteasome-independent ubiquitination pathway. We have identified a regulated interaction between parkin and Eps15, an adaptor protein that is involved in epidermal growth factor (EGF) receptor (EGFR) endocytosis and trafficking. Treatment of cells with EGF stimulates parkin binding to both Eps15 and the EGFR and promotes parkin-mediated ubiquitination of Eps15. Binding of the parkin ubiquitin-like (Ubl) domain to the Eps15 ubiquitin-interacting motifs (UIMs) is required for parkin-mediated Eps15 ubiquitination. Furthermore, EGFR endocytosis and degradation are accelerated in parkin-deficient cells, and EGFR signalling via the phosphoinositide 3-kinase (PI(3)K)-Akt pathway is reduced in parkin knockout mouse brain. We propose that by ubiquitinating Eps15, parkin interferes with the ability of the Eps15 UIMs to bind ubiquitinated EGFR, thereby delaying EGFR internalization and degradation, and promoting PI(3)K-Akt signalling. Considering the role of Akt in neuronal survival, our results have broad new implications for understanding the pathogenesis of Parkinson's disease.     

Iron and exercise induced alterations in antioxidant status. Protection by dietary milk proteins

Lipid peroxidation stress induced by iron supplementation can contribute to the induction of gut lesions. Intensive sports lead to ischemia reperfusion, which increases free radical production. Athletes frequently use heavy iron supplementation, whose effects are unknown. On the other hand, milk proteins have in vitro antioxidant properties, which could counteract these potential side effects. The main aims of the study were: (1) to demonstrate the effects of combined exercise training (ET) and iron overload on antioxidant status; (2) to assess the protective properties of casein in vivo; (3) to study the mechanisms involved in an in vitro model.

Antioxidant status was assessed by measuring the activity of antioxidant enzymes (superoxide dismutase (SOD); glutathione peroxidase (GSH-Px)), and on the onset of aberrant crypts (AC) in colon, which can be induced by lipid peroxidation. At day 30, all ET animals showed an increase in the activity of antioxidant enzymes, in iron concentration in colon mucosa and liver and in the number of AC compared to untrained rats. It was found that Casein's milk protein supplementation significantly reduced these parameters. Additional information on protective effect of casein was provided by measuring the extent of TBARS formation during iron/ascorbate-induced oxidation of liposomes. Free casein and casein bound to iron were found to significantly reduce iron-induced lipid peroxidation. The results of the overall study suggest that Iron supplementation during intensive sport training would decrease anti-oxidant status. Dietary milk protein supplementation could at least partly prevent occurrence of deleterious effects to tissue induced by iron overload.     

Homogeneous and nonradioactive high-throughput screening platform for the characterization of kinase inhibitors in cell lysates

Protein kinases are directly implicated in many human diseases; therefore, kinase inhibitors show great promises as new therapeutic drugs. In an effort to facilitate the screening and the characterization of kinase inhibitors, a novel application of the AlphaScreen technology was developed to monitor JNK activity from (1) purified kinase preparations and (2) endogenous kinase from cell lysates preactivated with different cytokines. The authors confirmed that both adenosine triphosphate (ATP) competitive as well as peptide-based JNK inhibitors were able to block the activity of both recombinant and HepG2 endogenous JNK activity. Using the same luminescence technique adapted for binding studies, the authors characterized peptide inhibitor mechanisms by measuring the binding affinity of the inhibitors for JNK. Because of the versatility of the technology, this cell-based JNK kinase assay could be adapted to other kinases and would represent a powerful tool to evaluate endogenous kinase activity and test a large number of potential inhibitors in a more physiologically relevant environment.     

Identification of a novel gene (HSN2) causing hereditary sensory and autonomic neuropathy type II through the Study of Canadian Genetic Isolates

Hereditary sensory and autonomic neuropathy (HSAN) type II is an autosomal recessive disorder characterized by impairment of pain, temperature, and touch sensation owing to reduction or absence of peripheral sensory neurons. We identified two large pedigrees segregating the disorder in an isolated population living in Newfoundland and performed a 5-cM genome scan. Linkage analysis identified a locus mapping to 12p13.33 with a maximum LOD score of 8.4. Haplotype sharing defined a candidate interval of 1.06 Mb containing all or part of seven annotated genes, sequencing of which failed to detect causative mutations. Comparative genomics revealed a conserved ORF corresponding to a novel gene in which we found three different truncating mutations among five families including patients from rural Quebec and Nova Scotia. This gene, termed "HSN2," consists of a single exon located within intron 8 of the PRKWNK1 gene and is transcribed from the same strand. The HSN2 protein may play a role in the development and/or maintenance of peripheral sensory neurons or their supporting Schwann cells.     

Bradykinin metabolism in rat hearts with left-ventricular hypertrophy following myocardial infarction

The aim of the present study was to assess the contribution of angiotensin I converting enzyme (ACE)and neutral endopeptidase (NEP) in the coronary degradation of bradykinin (BK) after left-ventricular hypertrophy following myocardial infarction (MI) in rats. Myocardial infarction was induced by left descendant coronary artery ligation, and the contribution of ACE and NEP in the degradation of exogenous BK after a single passage through the coronary bed was assessed at 2, 5, and 36 days post-MI. BK degradation rate (V(max)/Km) was found to be significantly lower in hearts at 36 days (3.30 +/- 0.28 min(-1)) compared with 2 days (4.39 +/- 0.32 min(-1)) for noninfarcted hearts, but this reduction was just above the statistical level of significance for post-MI hearts. In infarcted hearts, V(max)/Km was increased significantly 5 days post-MI (4.91 +/- 0.28 min(-1)) compared with the 2 and 36 day-groups (3.43 +/- 0.20 and 2.78 +/- 0.16 min(-1), respectively). The difference between noninfarcted and MI was significant only 2 days post-MI. Treatment with the vasopeptidase inhibitor, omapatrilat, showed that the relative contribution of ACE and NEP combined increased over time in infarcted hearts and became significantly higher 36 versus 2 days post-MI. Finally, the treatment with an ACE inhibitor (enalaprilat) and a NEP inhibitor (retrothiorphan) in the 36-day infarcted and noninfarcted hearts showed that the relative contribution of ACE in infarcted hearts was comparable with that of noninfarcted hearts, whereas the relative contribution of NEP was increased significantly in infarcted hearts. In conclusion, experimental MI in rats induces complex changes in the metabolism of exogenous BK. The changes resulted in an increased relative contribution of NEP 36 days after infarction.