Systematic proteome and proteostasis profiling in human Trisomy 21 fibroblast cells.

Down syndrome (DS) is mostly caused by a trisomy of the entire Chromosome 21 (Trisomy 21, T21). Here, we use SWATH mass spectrometry to quantify protein abundance and protein turnover in fibroblasts from a monozygotic twin pair discordant for T21, and to profile protein expression in 11 unrelated DS individuals and matched controls. The integration of the steady-state and turnover proteomic data indicates that protein-specific degradation of members of stoichiometric complexes is a major determinant of T21 gene dosage outcome, both within and between individuals. This effect is not apparent from genomic and transcriptomic data. The data also reveal that T21 results in extensive proteome remodeling, affecting proteins encoded by all chromosomes. Finally, we find broad, organelle-specific post-transcriptional effects such as significant downregulation of the mitochondrial proteome contributing to T21 hallmarks. Overall, we provide a valuable proteomic resource to understand the origin of DS phenotypic manifestations

Mesenchymal stem cells lack efficacy in the treatment of experimental autoimmune neuritis despite in vitro inhibition of T-cell proliferation.

Mesenchymal stem cells have been demonstrated to ameliorate experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis, prompting clinical trials in multiple sclerosis which are currently ongoing. An important question is whether this therapeutic effect generalises to other autoimmune neurological diseases. We performed two trials of efficacy of MSCs in experimental autoimmune neuritis (EAN) in Lewis (LEW/Han (M)Hsd) rats, a model of human autoimmune inflammatory neuropathies. No differences between the groups were found in clinical, histological or electrophysiological outcome measures. This was despite the ability of mesenchymal stem cells to inhibit proliferation of CD4+ T-cells in vitro. Therefore the efficacy of MSCs observed in autoimmune CNS demyelination models do not necessarily generalise to the treatment of other forms of neurological autoimmunity

Demyelination models in the spinal cord

Disruption of axonal conduction within the central nervous system has obvious, negative consequences on numerous functions, including the ability to execute movement successfully. One important cause of axonal conduction deficits is primary demyelination, that is, the loss of the myelin sheaths but sparing of the axons which they surround. Such demyelination leads to conduction deficits ranging from action potential slowing and loss of transmission fidelity, to conduction block, and this latter, most severe consequence is almost inevitably the first consequence of the loss of a whole internode(s) of myelin. Several methods have been developed to induce primary demyelination in the spinal cord and some of the more common of these will be discussed in this chapter. © 2011 Springer Science+Business Media, LLC

Mitochondrial damage and "plugging" of transport selectively in myelinated, small-diameter axons are major early events in peripheral neuroinflammation

BACKGROUND: Small-diameter, myelinated axons are selectively susceptible to dysfunction in several inflammatory PNS and CNS diseases, resulting in pain and degeneration, but the mechanism is not known. METHODS: We used in vivo confocal microscopy to compare the effects of inflammation in experimental autoimmune neuritis (EAN), a model of Guillain-Barré syndrome (GBS), on mitochondrial function and transport in large- and small-diameter axons. We have compared mitochondrial function and transport in vivo in (i) healthy axons, (ii) axons affected by experimental autoimmune neuritis, and (iii) axons in which mitochondria were focally damaged by laser induced photo-toxicity. RESULTS: Mitochondria affected by inflammation or laser damage became depolarized, fragmented, and immobile. Importantly, the loss of functional mitochondria was accompanied by an increase in the number of mitochondria transported towards, and into, the damaged area, perhaps compensating for loss of ATP and allowing buffering of the likely excessive Ca2+ concentration. In large-diameter axons, healthy mitochondria were found to move into the damaged area bypassing the dysfunctional mitochondria, re-populating the damaged segment of the axon. However, in small-diameter axons, the depolarized mitochondria appeared to "plug" the axon, obstructing, sometimes completely, the incoming (mainly anterograde) transport of mitochondria. Over time (~ 2 h), the transported, functional mitochondria accumulated at the obstruction, and the distal part of the small-diameter axons became depleted of functional mitochondria. CONCLUSIONS: The data show that neuroinflammation, in common with photo-toxic damage, induces depolarization and fragmentation of axonal mitochondria, which remain immobile at the site of damage. The damaged, immobile mitochondria can "plug" myelinated, small-diameter axons so that successful mitochondrial transport is prevented, depleting the distal axon of functioning mitochondria. Our observations may explain the selective vulnerability of small-diameter axons to dysfunction and degeneration in a number of neurodegenerative and neuroinflammatory disorders

Additional file 4: of Mitochondrial damage and “plugging” of transport selectively in myelinated, small-diameter axons are major early events in peripheral neuroinflammation

Video S4. High-power time-lapse video of axonal mitochondria labeled with TMRM on the day of onset of EAN taken 80 min upon exposing the saphenous nerve. Eighty minutes following the Additional file 3: Video S3, the focal accumulations of functional axonal mitochondria (yellow arrow) appear enlarged in comparison with the earlier time point. Anterograde mitochondrial movement in these axons seems unaffected. Notably, in an axon positioned between the two axons with accumulations (green arrow) and which is of larger diameter than the two indicated with yellow arrows, mitochondrial distribution and morphology appear normal. The video is shown in gray scale in order to improve contrast. (AVI 1353 kb

Origins of Gliogenic Stem Cell Populations Within Adult Skin and Bone Marrow

The generation of Schwann cells from precursors within adult skin and bone marrow is of significant clinical interest because of the opportunities for disease modelling and strategies for remyelination. Recent evidence has suggested that glial cells can be generated from (i) mesenchymal stem cells (MSCs) within adult bone marrow and (ii) skin-derived precursor cells (SKPs) within adult skin. However, there is a need to clarify the developmental mechanism whereby such multipotent adult stem cell populations generate glia. We used Wnt1-Cre/Rosa26RLacZ and Wnt1-Cre/Rosa26RYFP neural crest reporter mice to test the hypothesis that (i) MSCs and (ii) SKPs represent adult gliogenic precursor cells of neural crest origin. We demonstrate that, although labeled cells can be identified within long bone preparation, such cells are rarely found in marrow plugs. Moreover, we did not find evidence of a neural crest origin of bone marrow-derived MSCs and were not able to provide a developmental rationale for the derivation of glial cells from MSCs using this approach. In contrast, we provide robust evidence for the neural crest origin of SKPs derived from adult skin. These precursor cells reliably generate cells with a Schwann cell phenotype, expressing appropriate transcription factors and Schwann cell markers. We demonstrate multiple anatomical origins of gliogenic SKPs within adult skin. We conclude that SKPs, rather than bone marrow-derived MSCs, represent a more defined and developmentally rational source for the study and generation of Schwann cells from readily accessible adult tissues

Additional file 3: of Mitochondrial damage and “plugging” of transport selectively in myelinated, small-diameter axons are major early events in peripheral neuroinflammation

Video S3. High-power time-lapse video of axonal mitochondria labeled with TMRM on the day of onset of EAN taken immediately upon exposing the saphenous nerve. Focal accumulation of functional axonal mitochondria (yellow arrow) is observed, with mitochondria moving in anterograde direction. Distal to the accumulation, axons appear depleted of functional mitochondria. In contrast, mitochondrial distribution and morphology appears normal in another axon (green arrow) which is of larger caliber than the two axons affected by mitochondrial accumulation. The video is shown in gray scale in order to improve contrast. (AVI 3253 kb

Additional file 5: of Mitochondrial damage and “plugging” of transport selectively in myelinated, small-diameter axons are major early events in peripheral neuroinflammation

Video S5. High-power time-lapse video of axonal mitochondria labeled with TMRM immediately following laser-induced phototoxic damage to mitochondria. The side of the imaging field left to the white line was not exposed to photo-toxic damage. The imaging field to the right of the white line was exposed to laser-induced photo-toxic damage, using the red laser to specifically damage functional mitochondria. Notably, the number of mobile mitochondria transported into the area exposed to photo-toxic damage appears overwhelmingly biased in the favor of anterograde movement. (AVI 2466 kb