Le bleu de méthylène comme traitement potentiel de sclérose latérale amyotrophique : étude de modèles murins surexprimant la superoxyde dismutase ou la TDP-43

La sclérose latérale amyotrophique (SLA) est une maladie neurodegenerative incurable. Un seul médicament existe pour traiter la SLA et il ne fait que prolonger la durée de vie des patients de 3 à 6 mois, sans en diminuer les symptômes. Parmi les meilleurs modèles pour étudier la SLA, les souris S0D1G93A sont largement utilisées, notamment pour tester de nouveaux composés. Aussi, le modèle murin TDP-43 , récemment généré dans notre laboratoire, représente très bien la pathologie observée dans une autre sous-portion des patients atteints de SLA (protéinopathies TDP-43). Dans une tentative de découvrir un nouveau traitement pour la SLA, nous avons administré à des souris S0D1G93A et TDP-43 du bleu de méthylène, médicament connu pour traiter une variété des désordres neurologiques et ayant des propriétés neuroprotectrices toutes indiquées pour traiter la SLA. Nous l'avons aussi administré conjointement avec le lithium qui est connu pour avoir des effets synergiques avec certains composés

Core and region-enriched networks of behaviorally regulated genes and the singing genome

Songbirds represent an important model organism for elucidating molecular mechanisms that link genes with complex behaviors, in part because they have discrete vocal learning circuits that have parallels with those that mediate human speech. We found that ~10% of the genes in the avian genome were regulated by singing, and we found a striking regional diversity of both basal and singing-induced programs in the four key song nuclei of the zebra finch, a vocal learning songbird. The region-enriched patterns were a result of distinct combinations of region-enriched transcription factors (TFs), their binding motifs, and presinging acetylation of histone 3 at lysine 27 (H3K27ac) enhancer activity in the regulatory regions of the associated genes. RNA interference manipulations validated the role of the calcium-response transcription factor (CaRF) in regulating genes preferentially expressed in specific song nuclei in response to singing. Thus, differential combinatorial binding of a small group of activity-regulated TFs and predefined epigenetic enhancer activity influences the anatomical diversity of behaviorally regulated gene networks

Ablation of Proliferating Cells in the CNS Exacerbates Motor Neuron Disease Caused by Mutant Superoxide Dismutase

Proliferation of glia and immune cells is a common pathological feature of many neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). Here, to investigate the role of proliferating cells in motor neuron disease, SOD1G93A transgenic mice were treated intracerebroventicularly (ICV) with the anti-mitotic drug cytosine arabinoside (Ara-C). ICV delivery of Ara-C accelerated disease progression in SOD1G93A mouse model of ALS. Ara-C treatment caused substantial decreases in the number of microglia, NG2+ progenitors, Olig2+ cells and CD3+ T cells in the lumbar spinal cord of symptomatic SOD1G93A transgenic mice. Exacerbation of disease was also associated with significant alterations in the expression inflammatory molecules IL-1β, IL-6, TGF-β and the growth factor IGF-1

Cognitive and neural correlates of innovation in wild finches

Behavioral innovations are defined as novel solutions to problems encountered by animals in the wild. Innovativeness can facilitate survival in new or changing environments. Anthropization is a major perturbation that is expected to favor innovative animals. While innovation rate is known to vary geographically and with relative brain size in vertebrates, the environmental and molecular bases of innovation are largely unknown. The work presented in this thesis aims at elucidating some of the ultimate and proximate causes of innovation, specifically 1) how innovations appear in the wild and how urbanization influences them 2) what are the neuromolecular bases of innovation. We characterized innovation in the Barbados bullfinch Loxigilla barbadensis, a tame and innovative bird species. First, we found that innovations can spread among individuals in the field, but they also appear independently. We also showed that innovative problem-solving skills positively vary with the gradient of urbanization, along with boldness, neophobia and immunocompetence. To elucidate the neural bases of innovativeness, we compared L. barbadensis with its sister species in Barbados, the black-faced grassquit Tiaris bicolor. Both species are territorial and overlap in their habitat use, but are highly divergent in their foraging strategies, T. bicolor being shy and conservative. Following a battery of tests in captivity, we found that the two species differed sharply in their problem-solving skills and risk-taking behaviors, but were similar for all other measured traits. Molecular analyses revealed that genes related to synaptic activity were particularly differentially expressed between the species in the associative pallium (mesopallium, nidopallium). Genes related to neurogenesis and neuron signaling were more expressed in L. barbadensis and those differences were more pronounced in the nidopallium caudolaterale (NCL), a region thought to be functionally analogous to the mammalian prefrontal cortex. At a finer scale, we identified two groups of neurotransmitter receptors that were remarkably divergent: NMDA and metabotropic glutamate receptors. In particular, the GRIN2B:GRIN2A ratio differed, which is in accordance with the literature on mammalian cognition. Our results suggest precise molecular targets for a potential case of convergent evolution of cognition in birds and mammals.Les innovations comportementales sont définies comme étant de nouvelles solutions à des problèmes rencontrés par les animaux en nature. L'anthropisation est une cause de perturbation majeure qui est censée favoriser les animaux innovateurs. Au niveau proximal, l'innovation devrait être contrôlée par des propriétés neurales intrinsèques spécifiques. Toutefois, bien qu'il soit établi que le taux d'innovation varie géographiquement et en fonction et de la taille relative du cerveau chez les vertébrés, les bases environnementales et moléculaires de l'innovation sont largement inconnues. Les travaux présentés dans cette thèse visent à élucider certaines causes ultimes et proximales de l'innovation, à savoir 1) comment les innovations apparaissent en nature et comment l'urbanisation affecte l'innovation et 2) quelles sont les bases neuromoléculaires de l'innovation. Nous avons caractérisé l'innovation chez le sporophile de la Barbade Loxigilla barbadensis, une espèce d'oiseau innovatrice et facile à approcher. Premièrement, nous avons trouvé que les innovations peuvent se diffuser entre individus, mais aussi apparaître de façon indépendante. Nous avons également découvert que la capacité de résolution de problèmes variait positivement avec le gradient d'urbanisation, en même temps que la témérité, la néophobie et l'immunocompétence. Pour élucider les bases neurales de l'innovation, nous avons comparé L. barbadensis avec son espèce-sœur à la Barbade le sporophile cici T. bicolor. Les espèces sont toutes deux territoriales et se recoupent sur le terrain, mais sont hautement divergentes dans leurs stratégies d'alimentation, T. bicolor étant timide et conservateur. Suivant une batterie de tests comportementaux en captivité, nous avons montré que les deux espèces différaient fondamentalement dans leur capacité à résoudre des problèmes et leur comportement de prise de risque, mais qu'elles étaient similaires pour tous les autres traits mesurés. Nos analyses moléculaires ont révélé que les gènes reliés à l'activité synaptique étaient particulièrement différentiellement exprimés entre les deux espèces dans le pallium associatif (mésopallium et nidopallium). Les gènes associés à la neurogenèse et la signalisation synaptique étaient plus exprimés chez L. barbadensis et ces différences se sont avérées plus prononcées dans le nidopallium caudolaterale (NCL), une région considérée comme étant fonctionnellement analogue au cortex préfrontal chez les mammifères. À une échelle encore plus fine, nous avons identifié deux groupes de récepteurs de neurotransmetteurs qui étaient remarquablement divergents : les récepteurs de glutamate NMDA et métabotropiques. En particulier, le ratio GRIN2B:GRIN2A différerait entre les deux espèces, ce qui est en accord avec la littérature sur la cognition mammalienne. Nos résultats suggèrent des cibles moléculaires précises pour un cas potentiel d'évolution convergente de la cognition chez les oiseaux et les mammifères

Bajan Birds Pull Strings: Two Wild Antillean Species Enter the Select Club of String-Pullers

<div><p>String-pulling is one of the most popular tests in animal cognition because of its apparent complexity, and of its potential to be applied to very different taxa. In birds, the basic procedure involves a food reward, suspended from a perch by a string, which can be reached by a series of coordinated pulling actions with the beak and holding actions of the pulled lengths of string with the foot. The taxonomic distribution of species that pass the test includes several corvids, parrots and parids, but in other families, data are much spottier and the number of individuals per species that succeed is often low. To date, the association between string-pulling ability and other cognitive traits was never tested. It is generally assumed that string-pulling is a complex form of problem-solving, suggesting that performance on string-pulling and other problem-solving tasks should be correlated. Here, we show that individuals of two innovative species from Barbados, the bullfinch <i>Loxigilla barbadensis</i> and the Carib grackle <i>Quiscalus lugubris fortirostris</i>, pass the string-pulling test. Eighteen of the 42 bullfinches tested succeeded, allowing us to correlate performance on this test to that on several other behavioral measurements. Surprisingly, string-pulling in bullfinches was unrelated to shyness, neophobia, problem-solving, discrimination and reversal learning performance. Only two of 31 grackles tested succeeded, precluding correlational analyses with other measures but still, the two successful birds largely differed in their other behavioral traits.</p></div

Ablation of proliferating cells in CNS decreases lifespan of SOD1^G93A mice.

<p>Kaplan-Meier survival curve shows that transgenic mice Sod1^G93A (n = 7) treated with Ara-C between 75 and 115 days had a mean survival of 134 days while untreated SOD1^G93A (n = 9) had a mean survival of 141 days. Log-rank test shows that this difference is significant (<i>p</i> = 0.0081).</p

Modulation of the inflammatory response in Ara-C treated SOD1^G93A mice.

<p>Quantitative RT-PCR results (values are normalized to GADPH and relative to wild-type control treated with vehicle; no significant difference was found between wild-type controls treated with vehicle or M-CSF for any marker). Significant differences were found between Ara-C and vehicle treated SOD1^G93A in levels of mRNA for TGF-b1 (*<i>p</i> = 0.0148), IL-1b (**<i>p</i> = 0.0072), IL-6 (**<i>p</i> = 0.0014) and IGF-1 (*<i>p</i> = 0.0108). Note that all mRNA levels were significantly higher in vehicle treated transgenic mice compared to WT, treated or not (<i>p</i><0.0025), except for IL-4 (<i>p</i> = 0.7582). All values are mean ± SEM; <i>n</i>(WT) = 9, <i>n</i>(Tg-Vehicle) = 6, <i>n</i>(Tg-Ara-C) = 15.</p

Ara-C treatment caused a decrease in microglia, NG2+ progenitors, oligodendrocytes, astrocytes and T cells in the spinal cord of SOD1^G93A mice.

<p>Immunofluorescence for cell markers Iba1 (A), CD68 (B), NG2 (C), GFAP (D), CD3 (E) and Olig2 (F) in the lumbar spinal cord of mutant SOD1 transgenic mice treated with vehicle or Ara-C. (G) Quantification of Iba positive cells showed a 1.5 folds reduction of cells in Ara-C treated mice compared to controls (**<i>p</i> = 0.0086). (H) Quantification of CD68 marker showed a 1.5 folds reduction of cells in Ara-C treated mice compared to controls (**<i>p</i> = 0.0099). (I) Quantification of NG2+ marker showed a 1.7 folds reduction of cells in Ara-C treated mice compared to controls (<i>p</i> = 0.0713) (J) Quantification of GFAP marked cells showed a slightly reduced number of astrocytes (1.2 folds) in Ara-C treated mice compared to controls, although this result was not significant (<i>p</i> = 0.3430). (K) Quantification of Olig2 positive cells showed a 2.0 folds reduction of cells in Ara-C treated mice compared to controls (*<i>p</i> = 0.0236) (L) Quantification of CD3+ cells showed 3.8 folds reduction of cells in Ara-C treated mice compared to controls (*<i>p</i> = 0.0122). All mice were analyzed at 115 days. All values are means ± SEM. Scale bars: 100 µm.</p