In utero and lactational exposure to low-doses of the pyrethroid insecticide cypermethrin leads to neurodevelopmental defects in male mice-An ethological and transcriptomic study.

Accumulating evidence suggests that developmental exposure to environmental chemicals may modify the course of brain development, ultimately leading to neuropsychiatric / neurodegenerative disorders later in life. In the present study, we assessed the impact of one of the most frequently used pesticides in both residential and agricultural applications - the synthetic pyrethroid cypermethrin (CYP) - on developmental neurotoxicity (DNT). Female mice were perinatally exposed to low doses of CYP (5 and 20 mg/kg body weight) from gestation to postnatal day 15. Behavioral analyses were performed during the offspring's early life and during adulthood. Postnatal analyses revealed that perinatal exposure to CYP disturbed motor development without modifying sensory and communicative skills. We found that later in life, CYP-exposed offspring expressed maladaptive behaviors in response to highly challenging tasks and abnormal sociability. Transcriptomic analyses performed in the offspring's brain at the end of the exposure, highlighted mitochondrial dysfunction as a relevant pathomechanism underlying CYP-induced DNT. Interestingly, several genes involved in proteostasis maintenance were also shown to be dysregulated suggesting that alterations in biogenesis, folding, trafficking and degradation of proteins may significantly contribute to CYP-related DNT. From a regulatory perspective, this study highlights that behavioral and transcriptomic analyses are complementary tools providing useful direction for better DNT characterization, and as such, should be used together more systematically

Perinatal exposure to glufosinate ammonium herbicide impairs neurogenesis and neuroblast migration through cytoskeleton destabilization

Neurogenesis, a process of generating functional neurons from neural precursors, occurs throughout life in restricted brain regions such as the subventricular zone (SVZ). During this process, newly generated neurons migrate along the rostral migratory stream to the olfactory bulb to replace granule cells and periglomerular neurons. This neuronal migration is pivotal not only for neuronal plasticity but also for adapted olfactory based behaviors. Perturbation of this highly controlled system by exogenous chemicals has been associated with neurodevelopmental disorders. We reported recently that perinatal exposure to low dose herbicide glufosinate ammonium (GLA), leads to long lasting behavioral defects reminiscent of Autism Spectrum Disorder-like phenotype in the offspring (Laugeray, Herzine et al. 2014) . Herein, we demonstrate that perinatal exposure to low dose GLA induces alterations in neuroblast proliferation within the SVZ and abnormal migration from the SVZ to the olfactory bulbs. These disturbances are not only concomitant to changes in cell morphology, proliferation and apoptosis, but are also associated with transcriptomic changes. Therefore, we demonstrate for the first time that perinatal exposure to low dose GLA alters SVZ neurogenesis. Jointly with our previous work, the present results provide new evidence on the link between molecular and cellular consequences of early life exposure to the herbicide GLA and the onset of ASD-like phenotype later in life

Autisme, génétique et anomalies de la fonction synaptique

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Simultaneous two-voxel localized H-1-observed C-13-edited spectroscopy for in vivo MRS on rat brain at 9.4 T: Application to the investigation of excitotoxic lesions

International audienceC-13 spectroscopy combined with the injection of C-13-labeled substrates is a powerful method for the study of brain metabolism in vivo. Since highly localized measurements are required in a heterogeneous organ such as the brain, it is of interest to augment the sensitivity of C-13 spectroscopy by proton acquisition. Furthermore, as focal cerebral lesions are often encountered in animal models of disorders in which the two brain hemispheres are compared, we wished to develop a bi-voxel localized sequence for the simultaneous bilateral investigation of rat brain metabolism, with no need for external additional references. Two sequences were developed at 9.4 T: a bi-voxel H-1-(C-13) STEAM-POCE (Proton Observed Carbon Edited) sequence and a bi-voxel H-1-(C-13) PRESS-POCE adiabatically decoupled sequence with Hadamard encoding. Hadamard encoding allows both voxels to be recorded simultaneously, with the same acquisition time as that required for a single voxel. The method was validated in a biological investigation into the neuronal damage and the effect on the Tri Carboxylic Acid cycle in localized excitotoxic lesions. Following an excitotoxic quinolinate-induced localized lesion in the rat cortex and the infusion of U-C-13 glucose, two H-1-(C-13) spectra of distinct (4 x 4 x 4 mm(3)) voxels, one centred on the injured hemisphere and the other on the contralateral hemisphere, were recorded simultaneously. Two H-1 bi-voxel spectra were also recorded and showed a significant decrease in N-acetyl aspartate, and an accumulation of lactate in the ipsilateral hemisphere. The H-1-(C-13) spectra could be recorded dynamically as a function of time, and showed a fall in the glutamatelglutamine ratio and the presence of a stable glutamine pool, with a permanent increase of lactate in the ipsilateral hemisphere. This bi-voxel H-1-(C-13) method can be used to investigate simultaneously both brain hemispheres, and to perform dynamic studies. We report here the neuronal damage and the effect on the Tri Carboxylic Acid cycle in localized excitotoxic lesions

Multiple effects of the herbicide glufosinate-ammonium and its main metabolite on neural stem cells from the subventricular zone of newborn mice

International audienceThe globally used herbicide glufosinate-ammonium (GLA) is structurally analogous to the excitatory neurotransmitter glutamate, and is known to interfere with cellular mechanisms involved in the glutamatergic system. In this report, we used an in vitro model of murine primary neural stem cell culture to investigate the neurotoxicity of GLA and its main metabolite, 4-methylphosphinico-2-oxobutanoic acid (PPO). We demonstrated that GLA and PPO disturb ependymal wall integrity in the ventricular-subventricular zone (V-SVZ) and alter the neuro-glial differentiation of neural stem cells. GLA and PPO impaired the formation of cilia, with reduced Celsr2 expression after PPO exposure. GLA promoted the differentiation of neuronal and oligodendroglial cells while PPO increased B1 cell population and impaired neuronal fate of neural stem cells. These results confirm our previous in vivo report that developmental exposure to GLA alters neurogenesis in the SVZ, and neuroblast migration along the rostral migratory stream. They also highlight the importance of investigating the toxicity of pesticide degradation products. Indeed, not only GLA, but also its metabolite PPO disrupts V-SVZ homeostasis and provides a novel cellular mechanism underlying GLA-induced neurodevelopmental toxicity. Furthermore, we were able to demonstrate a neurotoxic activity of a metabolite of GLA different from that of GLA active substance for the very first time

Perinatal exposure to low dose glufosinate ammonium induces autism-like phenotypes in mice

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Characterization of seizures induced by acute exposure to an organophosphate herbicide, glufosinate-ammonium

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IMPLICATION D'UN GENE DU SPLICEOSOME DANS UN CAS DE DEFICIENCE MENTALE SEVERE ?

International audienceLa déficience mentale (DM) se définit par un quotient intellectuel inférieur à 70 associé à un déficit fonctionnel du comportement adaptatif apparu avant l'âge de 18 ans (American Psychiatric Association, 1994). Sa prévalence est estimée à 1-3% de la population mondiale et ses étiologies sont extrêmement hétérogènes. Cependant, 25 à 50% des DM sévères sont d'origine génétique. Les réarrangements chromosomiques équilibrés de novo sont associés à un risque croissant de DM ou de malformations congénitales, ce qui suggère que le phénotype observé est causé par la suppression, la perturbation ou l'inactivation d'un ou plusieurs gène(s) dans les régions des points de cassure. C'est grâce à l'étude de tels remaniements chromosomiques que de nombreux gènes de DM ont été identifiés. Nous rapportons ici l'analyse moléculaire de la translocation réciproque équilibrée [46, X, t (X; 3) (p22 ; q13)] de novo portée par une fillette qui présente une déficience mentale sévère et une dysmorphie faciale. Une étude par approche « whole genome sequencing » s'est révélée non informative, le point de cassure du chromosome 3 étant situé en territoire centromérique répété. L'analyse pangénomique par puce haute résolution Affymetrix (SNP6.0 GenomeWide Human) nous a permis d'exclure l'existence de remaniements chromosomiques significatifs pouvant être à l'origine du phénotype. L'analyse transcriptomique par puce Affymetrix (Human EXON1.0) objectivait la dérégulation de l'expression de nombreux gènes. Parmi ces gènes, la baisse du taux de transcrit de gènes de déficience mentale, tels que FMR1 (syndrome de l'X fragile), CRBN (DM héréditaire), MECP2 (Syndrome de Rett) ou encore KCNMA1 (DM et autisme) expliquent le phénotype DM de la fillette porteuse du remaniement. De plus, cinq gènes se trouvent sous-exprimés dans la région de point de cassure Xp22. Parmi eux, un gène code pour une sous-unité régulatrice du complexe permettant la transcription génique, le spliceosome. Les anomalies transcriptionnelles multiples observées résultent donc probablement de cette anomalie. Cependant, à ce jour nous sommes encore dans l'incapacité de choisir entre une anomalie primaire de ce gène, liée au point de cassure Xp22, ou une anomalie secondaire ayant pour conséquence une dérégulation transcriptionnelle entrainant une déficience mentale

Morphological effects observed at the end of the treatment period (PND15).

<p>Morphological effects observed at the end of the treatment period (PND15).</p

Adult CYP20-exposed offspring displayed maladaptive behavior in response to highly stressful conditions.

<p><b>A</b>: The openfield was used as a weakly challenging task. Total distance travelled in the apparatus (1–2), time spent and the mean speed in different parts of the openfield were used to assess emotional reactivity (3). <b>B</b>: Emotional reactivity in response to highly challenging environments was evaluated by confronting mice to a novel cage with no sawdust. Total distance travelled was monitored over the total duration of the test (1). Data were also analyzed on a minute-by minute basis (2–3). <b>C-D</b>: Emotional reactivity in response to highly challenging environments was evaluated in the forced swimming task and the tail suspension task. In each condition, total time spent immobile was scored over the total duration of the test (1) and on a minute-by-minute basis (2). <b>E</b>: Habituation to a second exposure to stressful environments was assessed by confronting mice to the forced swimming task 24h later the first trial. Performance on day 2 is depicted on (1) and (2), and habituation between day 1 and day 2 is depicted on (3) and (4). Data are mean +/- sem; n = 20–21 /group. *** p < 0.001, ** p < 0.01, *p < 0.05 and # p < 0.09.</p