Distinct Modes of Neuron Addition in Adult Mouse Neurogenesis

Adult neurogenesis is restricted to two distinct areas of the mammalian brain: the olfactory bulb (OB) and the dentate gyrus (DG). Despite its spatial restriction, adult neurogenesis is of crucial importance for sensory processing and learning and memory. Although it has been shown that tens of thousands of new neurons arrive in the OB and DG every day with about half of them surviving after integration, the total contribution of adult neurogenesis to the pre-existing network remains mostly unknown. This is because of previous approaches labeling only a small proportion of adult-generated neurons. Here, we used genetic fate mapping to follow the majority of adult-generated neurons over long periods. Our data demonstrate two distinct modes of neuron addition to the pre-existing network. In the glomerular layer of the OB, there is a constant net addition of adult-generated neurons reaching a third of the total neuronal population within 9 months. In contrast, adult neurogenesis contributes to only a minor fraction of the entire neuronal network in the granular cell layer of the OB and the DG. Although the fraction of adult generated neurons can be further increased by an enriched environment, it still remains a minority of the neuronal network in the DG. Thus, neuron addition is distinct and tightly regulated in the neuronal networks that incorporate new neurons life long

Functional properties of neurons derived from in vitro reprogrammed postnatal astroglia

With the exception of astroglia-like cells in the neurogenic niches of the telencephalic subependymal or hippocampal subgranular zone, astroglia in all other regions of the adult mouse brain do not normally generate neurons. Previous studies have shown, however, that early postnatal cortical astroglia in culture can be reprogrammed to adopt a neuronal fate after forced expression of Pax6, a transcription factor (TF) required for proper neuronal specification during embryonic corticogenesis. Here we show that also the proneural genes neurogenin-2 and Mash1 (mammalian achaete schute homolog 1) possess the ability to reprogram astroglial cells from early postnatal cerebral cortex. By means of time-lapse imaging of green fluorescent astroglia, we provide direct evidence that it is indeed cells with astroglial characteristics that give rise to neurons. Using patch-clamp recordings in culture, we show that astroglia-derived neurons acquire active conductances and are capable of firing action potentials, thus displaying hallmarks of true neurons. However, independent of the TF used for reprogramming, astroglia-derived neurons appear to mature more slowly compared with embryonic-born neurons and fail to generate a functional presynaptic output within the culturing period. However, when cocultured with embryonic cortical neurons, astroglia-derived neurons receive synaptic input, demonstrating that they are competent of establishing a functional postsynaptic compartment. Our data demonstrate that single TFs are capable of inducing a remarkable functional reprogramming of astroglia toward a truly neuronal identity

Elucidation of xenobiotic metabolism pathways in human skin and human skin models by proteomic profiling

Human skin has the capacity to metabolise foreign chemicals (xenobiotics), but knowledge of the various enzymes involved is incomplete. A broad-based unbiased proteomics approach was used to describe the profile of xenobiotic metabolising enzymes present in human skin and hence indicate principal routes of metabolism of xenobiotic compounds. Several in vitro models of human skin have been developed for the purpose of safety assessment of chemicals. The suitability of these epidermal models for studies involving biotransformation was assessed by comparing their profiles of xenobiotic metabolising enzymes with those of human skin

Pax6 interactions with chromatin and identification of its novel direct target genes in lens and forebrain.

Pax6 encodes a specific DNA-binding transcription factor that regulates the development of multiple organs, including the eye, brain and pancreas. Previous studies have shown that Pax6 regulates the entire process of ocular lens development. In the developing forebrain, Pax6 is expressed in ventricular zone precursor cells and in specific populations of neurons; absence of Pax6 results in disrupted cell proliferation and cell fate specification in telencephalon. In the pancreas, Pax6 is essential for the differentiation of α-, β- and δ-islet cells. To elucidate molecular roles of Pax6, chromatin immunoprecipitation experiments combined with high-density oligonucleotide array hybridizations (ChIP-chip) were performed using three distinct sources of chromatin (lens, forebrain and β-cells). ChIP-chip studies, performed as biological triplicates, identified a total of 5,260 promoters occupied by Pax6. 1,001 (133) of these promoter regions were shared between at least two (three) distinct chromatin sources, respectively. In lens chromatin, 2,335 promoters were bound by Pax6. RNA expression profiling from Pax6⁺/⁻ lenses combined with in vivo Pax6-binding data yielded 76 putative Pax6-direct targets, including the Gaa, Isl1, Kif1b, Mtmr2, Pcsk1n, and Snca genes. RNA and ChIP data were validated for all these genes. In lens cells, reporter assays established Kib1b and Snca as Pax6 activated and repressed genes, respectively. In situ hybridization revealed reduced expression of these genes in E14 cerebral cortex. Moreover, we examined differentially expressed transcripts between E9.5 wild type and Pax6⁻/⁻ lens placodes that suggested Efnb2, Fat4, Has2, Nav1, and Trpm3 as novel Pax6-direct targets. Collectively, the present studies, through the identification of Pax6-direct target genes, provide novel insights into the molecular mechanisms of Pax6 gene control during mouse embryonic development. In addition, the present data demonstrate that Pax6 interacts preferentially with promoter regions in a tissue-specific fashion. Nevertheless, nearly 20% of the regions identified are accessible to Pax6 in multiple tissues

Dendritic cells and allergy

Komórki dendrytyczne odgrywają kluczową rolę w regulacji aktywności układu immunologicznego. Celem pracy jest przedstawienie aktualnych poglądów na pochodzenie, biologię komórek dendrytycznych oraz znaczenie tych komórek w astmie oskrzelowej i immunoterapii.Dendritic cells (DC) are pivotal regulator of immune reactivity and immune tolerance. The aim of this paper is to present the current knowledge on the dendritic cell development, biology and their role in asthma and immunotherapy

New approaches for brain repair-from rescue to reprogramming.

The ability to repair or promote regeneration within the adult human brain has been envisioned for decades. Until recently, such efforts mainly involved delivery of growth factors and cell transplants designed to rescue or replace a specific population of neurons, and the results have largely been disappointing. New approaches using stem-cell-derived cell products and direct cell reprogramming have opened up the possibility of reconstructing neural circuits and achieving better repair. In this Review we briefly summarize the history of neural repair and then discuss these new therapeutic approaches, especially with respect to chronic neurodegenerative disorders.Roger Barker is funded by the NIHR Biomedical Research Centre in Cambridge, Cure PD, PDUK, European Research Council under the European Union’s Seventh Framework Programme: FP/2007-2013 NeuroStemcellRepair (no. 602278). Wellcome Trust MRC Stem Cell Institute and MRC UKRMP PSCP. He has received consultancy payment from FCDI and LCT. MG is funded by the German research foundation (CRC870, SPP1738, 1757, EXC1010 Synergy), The Ministry of Science and Research (MAIV), ERANET and the ERC (ChroNeuroRepair). Patent WO 2015/114059 A1. MP receives funding from the New York Stem Cell Foundation, the European Research Council under the European Union’s Seventh Framework Programme: FP/2007-2013 NeuroStemcellRepair (no. 602278) and ERC Grant Agreement no. 30971, the Swedish Research Council and the Strategic Research Area Multipark at Lund University Multipark. MP is a New York Stem Cell foundation Robertson Investigator. MP is the owner of Parmar Cells and co-inventor of patent 62/145,467

Repetitive injury and absence of monocytes promote astrocyte self-renewal and neurological recovery

Unlike microglia and NG2 glia, astrocytes are incapable of migrating to sites of injury in the posttraumatic cerebral cortex, instead relying on proliferation to replenish their numbers and distribution in the affected region. However, neither the spectrum of their proliferative repertoire nor their postinjury distribution has been examined in vivo. Using a combination of different thymidine analogs and clonal analysis in a model of repetitive traumatic brain injury, we show for the first time that astrocytes that are quiescent following an initial injury can be coerced to proliferate after a repeated insult in the cerebral cortex grey matter. Interestingly, this process is promoted by invasion of monocytes to the injury site, as their genetic ablation (using CCR2(-/-)mice) increased the number of repetitively dividing astrocytes at the expense of newly proliferating astrocytes in repeatedly injured parenchyma. These differences profoundly affected both the distribution of astrocytes and recovery period for posttraumatic behavior deficits suggesting key roles of astrocyte self-renewal in brain repair after injury

Mesenchymal Stem Cells Promote Oligodendroglial Differentiation in Hippocampal Slice Cultures

We have previously shown that soluble factors derived from mesenchymal stem cells (MSCs) induce oligodendrogenic fate and differentiation in adult rat neural progenitors (NPCs) in vitro. Here, we investigated if this pro-oligodendrogenic effect is maintained after cells have been transplanted onto rat hippocampal slice cultures, a CNS-organotypic environment. We first tested whether NPCs, that were pre-differentiated in vitro by MSC-derived conditioned medium, would generate oligodendrocytes after transplantation. This approach resulted in the loss of grafted NPCs, suggesting that oligodendroglial pre-differentiated cells could not integrate in the tissue and therefore did not survive grafting. However, when NPCs together with MSCs were transplanted in situ into hippocampal slice cultures, the grafted NPCs survived and the majority of them differentiated into oligodendrocytes. In contrast to the prevalent oligodendroglial differentiation in case of the NPC/MSC co-transplantation, naive NPCs transplanted in the absence of MSCs differentiated predominantly into astrocytes. In summary, the pro-oligodendrogenic activity of MSCs was maintained only after co-transplantation into hippocampal slice cultures. Therefore, in the otherwise astrogenic milieu, MSCs established an oligodendrogenic niche for transplanted NPCs, and thus, co-transplantation of MSCs with NPCs might provide an attractive approach to re-myelinate the various regions of the diseased CNS. Copyright (C) 2009 S. Karger AG, Base