Increased number of mucocytes in Aiptasia pallida following heat-induced bleaching

Poster (2012)

Establishment of endosymbiosis: The case of cnidarians and Symbiodinium

in Journal of Experimental Marine Biology and Ecology (2012), 420–421

The symbiosis between cnidarians and Symbiodinium algae (dinoflagellates) is the keystone responsible for the formation of the huge and important structures that are coral reefs. Today many environmental ... [more ▼]

The symbiosis between cnidarians and Symbiodinium algae (dinoflagellates) is the keystone responsible for the formation of the huge and important structures that are coral reefs. Today many environmental and/or anthropogenic threats compromise this tight relationship and lead to more frequent events of drastic loss of Symbiodinium pigments and eventually of algae themselves from cnidarians, better known as cnidarian bleaching. While the mechanisms underlying the collapse of the algae–coral symbiosis are progressively getting unraveled, the understanding of the mechanisms involved in the de novo infection of bleached cnidarians by Symbiodinium remains elusive. In this review, we describe the various steps needed to establish a stable symbiotic relationship between Symbiodinium and cnidarians. We review the mechanisms implicated in host–symbiont recognition and in symbiosome formation and persistence, with a special emphasis on the role played by lectins and Rab proteins. A better understanding of these molecular mechanisms may contribute to the development of strategies to promote post-bleaching recovery of corals. [less ▲]

Evaluation of long-term functional deficits following transient cerebral ischemia in two mouse strains

Poster (2011, November 03)

Nowadays, no suitable animal model exists to assess long-term disabilities after cerebral ischemia. The aim of this study was to compare long-term behavioral and histological differences between two ... [more ▼]

Nowadays, no suitable animal model exists to assess long-term disabilities after cerebral ischemia. The aim of this study was to compare long-term behavioral and histological differences between two common mouse strains (129S2/SvPasCrl and C57BL6H) after 30 minutes of middle cerebral artery occlusion (MCAo). Sensorimotor assessments were conducted at one and at three weeks post-surgery using accelerated Rotarod and open-field locomotion. Long-term behavioral testing began four weeks after MCAo using operant conditioning in a progressive fixed-ratio (FR) schedule. Experiments ended with volumetric determination of the infarcted area using NeuN immunostaining. Although no effect of ischemia was detected in 129S2 mice using these tests, in C57 mice, results showed obvious short-term motor and locomotor deficits. Furthermore, subtle but persistent disturbances of endurance and executive functioning were recorded by the progressive schedule tests but not highlighted by sensorimotor tests. Ischemic lesion extended to the dorsolateral part of the striatum in both strains and recurrent cortical damages were also observed in C57 mice. All those results are in accordance with inherent morphological and behavioral features of each strain. Since the motor cortex is spared by 30 minutes MCAo, functional disabilities could be related to striatal damages. In conclusion, C57BL/6H mouse strain, by offering an acceptable survival rate and enough sensitivity to MCAo, seems to be a mouse strain suitable to evaluate long-term deficits and possible functional recovery after cerebral ischemia. [less ▲]

Increased gastrodermal mitosis after bleaching in the sea anemone A. pallida

Poster (2010, December)

A short upstream promoter region mediates transcriptional regulation of the mouse doublecortin gene in differentiating neurons.

in BMC Neuroscience (2010), 11(1), 64

ABSTRACT: BACKGROUND: Doublecortin (Dcx), a MAP (Microtubule-Associated Protein), is transiently expressed in migrating and differentiating neurons and thereby characterizes neuronal precursors and ... [more ▼]

ABSTRACT: BACKGROUND: Doublecortin (Dcx), a MAP (Microtubule-Associated Protein), is transiently expressed in migrating and differentiating neurons and thereby characterizes neuronal precursors and neurogenesis in developing and adult neurogenesis. In addition, reduced Dcx expression during development has been related to appearance of brain pathologies. Here, we attempt to unveil the molecular mechanisms controlling Dcx gene expression by studying its transcriptional regulation during neuronal differentiation. RESULTS: To determine and analyze important regulatory sequences of the Dcx promoter, we studied a putative regulatory region upstream from the mouse Dcx coding region (pdcx2kb) and several deletions thereof. These different fragments were used in vitro and in vivo to drive reporter gene expression. We demonstrated, using transient expression experiments, that pdcx2kb is sufficient to control specific reporter gene expression in cerebellar cells and in the developing (E14.5) brain. We determined the temporal profile of Dcx promoter activity during neuronal differentiation of mouse embryonic stem cells (mESC) and found that transcriptional activation of the Dcx gene varies along with neuronal differentiation of mESC. Deletion experiments and sequence comparison of Dcx promoters across rodents, human and chicken revealed the importance of a highly conserved sequence in the proximal region of the promoter required for specific and strong expression in neuronal precursors and young neuronal cells. Further analyses revealed the presence in this short sequence of several conserved, putative transcription factor binding sites: LEF/TCF (Lymphoid Enhancer Factor/T-Cell Factor) which are effectors of the canonical Wnt pathway; HNF6/OC2 (Hepatocyte Nuclear Factor-6/Oncecut-2) members of the ONECUT family; and NF-Y/CAAT (Nuclear Factor-Y). CONCLUSIONS: Studies of Dcx gene regulatory sequences using native, deleted and mutated constructs suggest that fragments located upstream of the Dcx coding sequence are sufficient to induce specific Dcx expression in vitro: in heterogeneous differentiated neurons from mESC, in primary mouse cerebellar neurons (PND3) and in organotypic slices cultures. Furthermore, a region in the 3'-end region of the Dcx promoter is highly conserved across several species and exerts positive control on Dcx transcriptional activation. Together, these results indicate that the proximal 3'-end region of the mouse Dcx regulatory sequence is essential for Dcx gene expression during differentiation of neuronal precursors. [less ▲]

Photoacclimation responses of a symbiotic sea anemone reveal an important host cellular plasticity

Poster (2010)

The high productivity of coral reef ecosystems is largely attributed to the mutualistic symbiosis between reef-building corals and their intracellular dinoflagellate in the genus Symbiodinium commonly ... [more ▼]

The high productivity of coral reef ecosystems is largely attributed to the mutualistic symbiosis between reef-building corals and their intracellular dinoflagellate in the genus Symbiodinium commonly referred to as zooxanthellae. These photosynthetic algae translocate a majority of their photosynthetically fixed carbon to the host and contribute to their metabolic needs and the calcification process. <i>Symbiodinium</i> must maintain a balance between the energy derived from the light reactions in the chloroplast and the amount of energy used during dark reactions and other metabolic processes. Nevertheless, in the natural environment the holobiont have to cope with daily and seasonal changes in light intensity, upsetting that balance and creating a stress that induces a physiological response (photoacclimation) to optimize growth rates. After a ten day exposition to high and very low light intensity, morphological and photophysiological analysis conducted on the symbiotic sea anemone, Anemonia manjano, reveal significant modifications of the host tissues ultrastructure and the Symbiodinium metabolic processes (photosynthesis, respiration). Those results highlight particularly important gastrodermal and ectodermal plasticity in which symbiotic cnidarians acclimate to the Symbiodinium physiological status (mainly photosynthesis) by varying the density of particular cellular types (e.g.: cnidocytes, gastrodermal cells) contained in their tissues. [less ▲]

NOS Activity in the sea anemone following light-induced stress.

Poster (2009, October 28)

Subchronic Alpha-Linolenic Acid Treatment Enhances Brain Plasticity and Exerts an Antidepressant Effect: A Versatile Potential Therapy for Stroke.

in Neuropsychopharmacology : Official Publication of the American College of Neuropsychopharmacology (2009)

Omega-3 polyunsaturated fatty acids are known to have therapeutic potential in several neurological and psychiatric disorders. However, the molecular mechanisms of action underlying these effects are not ... [more ▼]

Omega-3 polyunsaturated fatty acids are known to have therapeutic potential in several neurological and psychiatric disorders. However, the molecular mechanisms of action underlying these effects are not well elucidated. We previously showed that alpha-linolenic acid (ALA) reduced ischemic brain damage after a single treatment. To follow-up this finding, we investigated whether subchronic ALA treatment promoted neuronal plasticity. Three sequential injections with a neuroprotective dose of ALA increased neurogenesis and expression of key proteins involved in synaptic functions, namely, synaptophysin-1, VAMP-2, and SNAP-25, as well as proteins supporting glutamatergic neurotransmission, namely, V-GLUT1 and V-GLUT2. These effects were correlated with an increase in brain-derived neurotrophic factor (BDNF) protein levels, both in vitro using neural stem cells and hippocampal cultures and in vivo, after subchronic ALA treatment. Given that BDNF has antidepressant activity, this led us to test whether subchronic ALA treatment could produce antidepressant-like behavior. ALA-treated mice had significantly reduced measures of depressive-like behavior compared with vehicle-treated animals, suggesting another aspect of ALA treatment that could stimulate functional stroke recovery by potentially combining acute neuroprotection with long-term repair/compensatory plasticity. Indeed, three sequential injections of ALA enhanced protection, either as a pretreatment, wherein it reduced post-ischemic infarct volume 24 h after a 1-hour occlusion of the middle cerebral artery or as post-treatment therapy, wherein it augmented animal survival rates by threefold 10 days after ischemia.Neuropsychopharmacology advance online publication, 29 July 2009; doi:10.1038/npp.2009.84. [less ▲]

Differential organ-specific response of heat-shock protein 90a in fish following contamination by PCB169

Poster (2008, October)

Effects of the transcription factor HNF-6 on double cortin promoter regulation in mouse embryonic stem cells

Poster (2008)