Loss of neuronal 3d chromatin organization causes transcriptional and behavioural deficits related to serotonergic dysfunction

The interior of the neuronal cell nucleus is a highly organized three-dimensional (3D) structure where regions of the genome that are linearly millions of bases apart establish sub-structures with specialized functions. To investigate neuronal chromatin organization and dynamics in vivo, we generated bitransgenic mice expressing GFP-tagged histone H2B in principal neurons of the forebrain. Surprisingly, the expression of this chimeric histone in mature neurons caused chromocenter declustering and disrupted the association of heterochromatin with the nuclear lamina. The loss of these structures did not affect neuronal viability but was associated with specific transcriptional and behavioural deficits related to serotonergic dysfunction. Overall, our results demonstrate that the 3D organization of chromatin within neuronal cells provides an additional level of epigenetic regulation of gene expression that critically impacts neuronal function. This in turn suggests that some loci associated with neuropsychiatric disorders may be particularly sensitive to changes in chromatin architecture

Sublayer- and cell-type-specific neurodegenerative transcriptional trajectories in hippocampal sclerosis

Altres ajuts: Fundación Tatiana Pérez de Guzman el Bueno; SynCogDis Network (SAF2014-52624-REDT, SAF2017-90664-REDT); Human Frontiers Science Program (HFSP RGP0022/2013); Fondo Europeo de Desarrollo Regional (FEDER).Hippocampal sclerosis, the major neuropathological hallmark of temporal lobe epilepsy, is characterized by different patterns of neuronal loss. The mechanisms of cell-type-specific vulnerability and their progression and histopathological classification remain controversial. Using single-cell electrophysiology in vivo and immediate-early gene expression, we reveal that superficial CA1 pyramidal neurons are overactive in epileptic rodents. Bulk tissue and single-nucleus expression profiling disclose sublayer-specific transcriptomic signatures and robust microglial pro-inflammatory responses. Transcripts regulating neuronal processes such as voltage channels, synaptic signaling, and cell adhesion are deregulated differently by epilepsy across sublayers, whereas neurodegenerative signatures primarily involve superficial cells. Pseudotime analysis of gene expression in single nuclei and in situ validation reveal separated trajectories from health to epilepsy across cell types and identify a subset of superficial cells undergoing a later stage in neurodegeneration. Our findings indicate that sublayer- and cell-type-specific changes associated with selective CA1 neuronal damage contribute to progression of hippocampal sclerosis

Brain size regulations by cbp haploinsufficiency evaluated by in-vivo MRI based volumetry

The Rubinstein-Taybi Syndrome (RSTS) is a congenital disease that affects brain development causing severe cognitive deficits. In most cases the disease is associated with dominant mutations in the gene encoding the CREB binding protein (CBP). In this work, we present the first quantitative analysis of brain abnormalities in a mouse model of RSTS using magnetic resonance imaging (MRI) and two novel self-developed automated algorithms for image volumetric analysis. Our results quantitatively confirm key syndromic features observed in RSTS patients, such as reductions in brain size (-16.31%, p < 0.05), white matter volume (-16.00%, p < 0.05), and corpus callosum (-12.40%, p < 0.05). Furthermore, they provide new insight into the developmental origin of the disease. By comparing brain tissues in a region by region basis between cbp(+/-) and cbp(+/+) littermates, we found that cbp haploinsufficiency is specifically associated with significant reductions in prosencephalic tissue, such us in the olfactory bulb and neocortex, whereas regions evolved from the embryonic rhombencephalon were spared. Despite the large volume reductions, the proportion between gray-, white-matter and cerebrospinal fluid were conserved, suggesting a role of CBP in brain size regulation. The commonalities with holoprosencephaly and arhinencephaly conditions suggest the inclusion of RSTS in the family of neuronal migration disorders.We are grateful to Begona Fernandez for her excellent technical assistance. We would like to thank S. Sawiak (Wolfson Imaging Centre, University of Cambridge, Cambridge, United Kingdom) for the mouse brain tissue probability maps and the SPMmouse plug-in, and to N. Kovacevic (Mouse Imaging Centre, Hospital for Sick Children, Toronto, Ontario, Canada) for the atlas of the mouse brain. Supported by grants from the Spanish MINECO to S.C. (BFU 2012-39958) and MINECO and FEDER to D.M. (TEC 2012-33778) and from MINECO (SAF2011-22855) and Generalitat Valenciana (Prometeo/2012/005) to A.B. The Instituto de Neurociencias is "Centre of Excellence Severo Ochoa".Ateca Cabarga, JC.; Cosa, A.; Pallares, V.; Lopez-Atalaya, JP.; Barco, A.; Canals, S.; Moratal Pérez, D. (2015). Brain size regulations by cbp haploinsufficiency evaluated by in-vivo MRI based volumetry. Scientific Reports. 5. https://doi.org/10.1038/srep16256S5Rubinstein, J. H. & Taybi, H. Broad thumbs and toes and facial abnormalities. A possible mental retardation syndrome. Am J Dis Child 105, 588–608 (1963).Van Belzen, M., Bartsch, O., Lacombe, D., Peters, D. J. & Hennekam, R. C. Rubinstein-Taybi syndrome (CREBBP, EP300). Eur J Hum Genet. 19, preceeding 118–120 (2011).Hennekam, R. C. 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The brain-specific tissue-type plasminogen activator inhibitor, neuroserpin, protects neurons against excitotoxicity both in vitro and in vivo.

Considering its brain-specific expression, neuroserpin (NS), a potent inhibitor of tissue-type plasminogen activator (tPA), might be a good therapeutic target to limit the pro-excitotoxic effects of tPA within the cerebral parenchyma, without affecting the benefit from thrombolysis in stroke patients. Here, we aimed at determining the mechanisms of action responsible for the previously reported neuroprotective activity of NS in rodent experimental cerebral ischemia. First, we show in vivo that exogenous NS protects the cortex and the striatum against NMDA-induced injury. Then, the cellular mechanisms of this neuroprotection were investigated in primary cultures of cortical neurons. We show that NS fails to prevent serum deprivation-induced apoptotic neuronal death, while it selectively prevents NMDA- but not AMPA-induced excitotoxicity. This beneficial effect is associated to a decrease in NMDA receptor-mediated intracellular calcium influx. Altogether, these data suggest that an overexpression of neuroserpin in the brain parenchyma might limit the deleterious effect of tPA on NMDA receptor-mediated neuronal death, which occurs following experimental ischemia

Histone acetylation deficits in lymphoblastoid cell lines from patients with Rubinstein-Taybi syndrome.

ABSTRACT Background RubinsteineTaybi syndrome (RSTS) is a congenital neurodevelopmental disorder defined by postnatal growth deficiency, characteristic skeletal abnormalities and mental retardation and caused by mutations in the genes encoding for the transcriptional co-activators with intrinsic lysine acetyltransferase (KAT) activity CBP and p300. Previous studies have shown that neuronal histone acetylation is reduced in mouse models of RSTS. Methods The authors identified different mutations at the CREBBP locus and generated lymphoblastoid cell lines derived from nine patients with RSTS carrying distinct CREBBP mutations that illustrate different grades of the clinical severity in the spectrum of the syndrome. They next assessed whether histone acetylation levels were altered in these cell lines. Results The comparison of CREBBP-mutated RSTS cell lines with cell lines derived from patients with an unrelated mental retardation syndrome or healthy controls revealed significant deficits in histone acetylation, affecting primarily histone H2B and histone H2A. The most severe defects were observed in the lines carrying the whole deletion of the CREBBP gene and the truncating mutation, both leading to a haploinsufficiency state. Interestingly, this deficit was rescued by treatment with an inhibitor of histone deacetylases (HDACi). Conclusions The authors\u2019 results extend to humans the seminal observations in RSTS mouse models and point to histone acetylation defects, mainly involving H2B and H2A, as relevant molecular markers of the disease