Abnormalities in the cerebellum and brainstem in homozygous Lurcher mice

The lurcher mutation induces Purkinje cell degeneration in heterozygous mice, and neonatal death in homozygous animals. Using the D6Mit16 Simple Sequence Length Polymorphic marker in F2 hybrids between AKR +/+ mice and B6+/Lc mice, homozygous lurcher fetuses and newborns as well as heterozygous and normal littermates were identified, and their brain morphology was analysed. In homozygous lurcher embryos at embryonic day 18 and neonates the cerebellum was hypotrophic, particularly in the posterior half. Purkinje cells were smaller in the whole cerebellum and showed a maturational delay. Calretinin-positive cells were less frequently observed in the depth of the vermis than in normal mice. Both Purkinje cells and the vermal calretinin- positive cells were more abnormal in fetuses at day 19 and newborn mutants than one day earlier. An abnormal number of pycnotic cells were observed in the cerebellum, especially in newborn mutants. Brainstem abnormalities were characterized by abnormal curvature, caudal displacement of the pontine gray nuclei which were located caudally along the ventral border of the superior olivary complex, a drastic decrease in Purkinje cell axons in all the vestibular nuclei and the presence of dystrophic processes in at least two calbindin-positive cell groups of the dorsal pontine region. These results show that the mutation, which is semidominant in Purkinje cells, is recessive in other cell groups of the cerebellum and brainstem. They reveal that the sequence leading to Purkinje cell death appears to be similar in homozygous and heterozygous mice, although occurring earlier and worsening more quickly in the former. Lastly, they confirm the absence of effect of the mutation on the neurons of the inferior olivary complex.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

GTP-cyclohydrolase-I like immunoreactivity in rat brain

GTPCH-I immunoreactive structures in the rat brain were studied using a polyclonal antibody raised in the chick. General mapping was made using the avidin-biotin-peroxidase technique and compared with the distribution of tyrosine hydroxylase and serotonin immunoreactivities. Double immunofluorescence was performed in order to establish real intracellular colocalization. GTPCH-I immunoreactivity was generally found to be low. Immunostained neurons were present in all the serotonin cell groups. In catecholaminergic neurons, although tyrosine hydroxylase immunoreactivity was always very high, GTPCH-I immunoreactivity was extremely variable, from relatively strong (substantia nigra, ventral tegmental area) to low (locus coeruleus, caudal part of the hypothalamus), extremely low (rostral hypothalamus, ventral brainstem) or almost absent (dorsal brainstem, some hypothalamic nuclei). When feasible, double immunolabeling revealed that all the serotonin cells and most of the tyrosine hydroxylase cells were also expressing GTPCH-I. Our results argue in favor of a regulation of tyrosine hydroxylase activity by the intracellular synthesis of BH4.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Pterin-4α-carbinolamine dehydratase in rat brain. I. Patterns of co-localization with tyrosine hydroxylase

The bifunctional protein, PCD/DCoH, is both a pterin-4α-carbinolamine dehydratase (PCD) and a dimerization cofactor of the hepatic nuclear factor 1α (DCoH). In association with brain tyrosine hydroxylase (TH), which is required for dopamine synthesis, PCD catalyses dehydration and thus recycling of the cofactor tetrahydrobiopterin (BH4). PCD immunoreactivity in the catecholaminergic system of the rat brain was studied using a rabbit polyclonal antibody. Double immunofluorescence was performed to establish intracellular co-localization with TH. PCD immunoreactivity was found to be high and consistently present in all the neuron groups expressing TH. More than 90% of the TH+ cells were also expressing PCD. The highest co-expression (99-100% of TH+ cells) was observed in pontine catecholaminergic cell groups including locus coeruleus. Lower co-expression was observed in substantia nigra (17% of TH+ cells without PCD) and particularly in arcuate nucleus (41% of TH+ cells without PCD). Our results argue in favor of a generalized recycling of BH4 in catecholaminergic neurons except when the neuron terminal field is located outside the blood-brain barrier. The respective roles of synthesis and recycling of BH4 in the control of TH activity are discussed. Copyright (C) 2000 Elsevier Science B.V.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Chronic intoxication with 3-nitropropionic acid in rats induces the loss of striatal dopamine terminals without affecting nigral cell viability.

3-Nitropropionic acid (3NP) is a succinate dehydrogenase inhibitor allowing the generation of animal models of Huntington's disease. In the present study, we found that a 5-day continuous chronic infusion of 3NP produces loss of [3H]mazindol binding and tyrosine hydroxylase (TH) immunoreactivity in the striatal area of degeneration. This loss of dopamine terminals was not due to a loss of nigral neurons since the expression of TH as well as the number of TH-expressing neurons remained unaltered in the substantia nigra of rats treated by 3NP. This suggests that the 3NP-induced dopamine terminal loss is secondarily related to the striatal degeneration andlor to a direct effect of 3NP on striatal terminals and not to a primary effect on nigral cells.Comparative StudyJournal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Immunohistochemical localisation of pterin-4α-carbinolamine dehydratase in rat peripheral organs

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Striatal and cortical neurochemical changes induced by chronic metabolic compromise in the 3-nitropropionic model of Huntington's disease.

In the present study, we aimed to determine the time-course of neurochemical changes occurring following metabolic impairments produced by 3-nitropropionic (3NP) acid in a rat model of Huntington's disease. We found that the occurrence of striatal lesions was accompanied by (1) strong transcriptional alterations within the degenerative lateral striatum, (2) receptor upregulations within the preserved medial striatum, and (3) transcriptional increases within the unaltered cerebral cortex. These phenomena were preceded by transcriptional modifications in striatal subareas prone to degeneration even before the lesion was visible but not in the overlying cortex, known to be spared in this model. Of great interest, the density of A(2A) receptor binding sites, located on striato-pallidal neurons, was (1) downregulated at the time of worsening of symptoms and (2) strongly upregulated within the spared medial striatum after the lesion occurrence. This study therefore highlights the differential neurochemical responses produced by 3NP depending on the fate of the metabolically inhibited area and strongly suggests the involvement of A(2A) receptors in the development of striatal pathology under metabolic compromise.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Spreading Dynamics of Biomimetic Actin Cortices

Reconstituted systems mimicking cells are interesting tools for understanding the details of cell behavior. Here, we use an experimental system that mimics cellular actin cortices, namely liposomes developing an actin shell close to their inner membrane, and we study their dynamics of spreading. We show that depending on the morphology of the actin shell inside the liposome, spreading dynamics is either reminiscent of a bare liposome (in the case of a sparse actin shell) or of a cell (in the case of a continuous actin shell). We use a mechanical model that qualitatively accounts for the shape of the experimental curves. From the data on spreading dynamics, we extract characteristic times that are consistent with mechanical estimates. The mechanical characterization of such stripped-down experimental systems paves the way for a more complex design closer to a cell. We report here the first step in building an artificial cell and studying its mechanics

Distribution of SV2C mRNA and protein expression in the mouse brain with a particular emphasis on the basal ganglia system.

Synaptic vesicle 2 proteins (SV2), SV2A, SV2B and SV2C, are integral proteins localized on the surface of synaptic vesicles in all neurons. SV2 proteins appear to play an important, but not yet fully understood role in synaptic vesicle exocytosis and neurotransmitter release. Moreover, SV2 seems to be the receptor of the botulinum neurotoxin A. In the present study, using single and double-labeling fluorescent immunohistochemistry and in situ hybridization we have identified the brain pattern of SV2C mRNA and protein expression in mice. Our results indicated that SV2C protein was expressed in a small subset of brain regions including the olfactory bulb, olfactory tubercle, nucleus accumbens, caudate-putamen, ventral pallidum, globus pallidus, substantia nigra and the ventral tegmental area. These results were confirmed by means of in situ hybridization, except for the globus pallidus and the substantia nigra pars reticulata, in which no labeling was found, suggesting that SV2C-positive fibers in these areas are terminals of striatal projecting neurons. In the striatum, we found that, in addition to its presence in the projection neurons, SV2C was densely expressed in a fraction (around 45%) of cholinergic interneurons. In addition, our data also showed that SV2C was densely expressed in most dopaminergic neurons in the substantia nigra pars compacta and the ventral tegmental area (more than 70% of the dopaminergic neurons analyzed were SV2C-positive). Altogether, our results suggest that SV2C may contribute to the regulation of neurotransmitter release and synaptic transmission in the basal ganglia including cholinergic striatal interneurons and nigro-striatal/mesolimbic dopamine neurons.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Differential expression of calbindin and calmodulin in motoneurons after hypoglossal axotomy.

Axotomy induces a profound modification of Ca2+ homeostasis in injured neurons which may lead to neuronal death. Remarkably, after axotomy and resection of the hypoglossal nerve, 65-75% of the hypoglossal motoneurons survive in the long term and this suggests some adaptive mechanisms compensating the massive calcium influx. As potential components of this adaptation, we have examined calmodulin and calbindin-D28k by in situ hybridisation and immunohistochemistry in motoneurons of the rat after hypoglossal nerve transection. Neuronal calbindin mRNA and protein content was low in normal state, transiently increased to 200% of the basal expression at 8 days post-operation (dpo), then declined to normal again until 28 dpo. Calmodulin mRNA was highly expressed in normal hypoglossal motoneurons and remained constant after axotomy. Calmodulin protein immunoreactivity, however, was transiently decreased in axotomised motoneurons suggesting post-transcriptional modification. The upregulation of calbindin expression may facilitate the survival of injured motoneurons.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Death of cortical and striatal neurons induced by mitochondrial defect involves differential molecular mechanisms.

An important aspect of Huntington's disease (HD) pathogenesis which may have important therapeutic implications is that the cellular events leading to cell death may be different in cortical and striatal neurons. In the present study, we characterized cellular changes in cortical and striatal neurons treated with the mitochondrial toxin 3-nitropropionic acid (3NP) in culture. Degeneration induced by 3NP was similar in both striatal and cortical neurons as observed using markers of cell viability and DNA fragmentation. However, in striatal neurons, 3NP produced a marked delocalization of Bad, Bax, cytochrome c and Smac while this was not observed in cortical neurons. Death of striatal neurons was preceded by activation of calpain and was blocked by calpain inhibitor I. In cortical neurons, calpain was not activated and calpain inhibitor I was without effect. In both cell types, caspase-9 and -3 were not activated by 3NP and the caspase inhibitor zVAD-fmk did not provide neuroprotective effect. Interestingly, treatment with staurosporine (STS) triggered caspase-9 and -3 in cortical and striatal cells, suggesting that the molecular machinery related to caspase-dependent apoptosis was functional in both cell types even though this machinery was not involved in 3NP toxicity. The present results clearly demonstrate that under mitochondrial inhibition, striatal and cortical neurons die through different pathways. This suggests that mitochondrial defects in HD may trigger the death of cortical and striatal neurons through different molecular events.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe