Hdac6 deletion delays disease progression in the SOD1G93A mouse model of ALS

Defects in axonal transport are thought to contribute to the pathogenesis of neurodegenerative disease. Because α-tubulin acetylation facilitates axonal transport, inhibition of the α-tubulin deacetylating enzymes, histone deacetylase 6 (Hdac6) and silent information regulator 2 (Sirt2), is thought to be an interesting therapeutic strategy for these conditions. Amyotrophic lateral sclerosis (ALS) is a one such rapidly progressive and fatal neurodegenerative disorder, in which axonal transport defects have been found in vitro and in vivo. To establish whether the inhibition of Hdac6 or Sirt2 may be of interest for ALS treatment, we investigated whether deleting Hdac6 or Sirt2 from the superoxide dismutase 1, SOD1G93A mouse affects the motor neuron degeneration in this ALS model. Deletion of Hdac6 significantly extended the survival of SOD1G93A mice without affecting disease onset, and maintained motor axon integrity. This protective effect was associated with increased α-tubulin acetylation. Deletion of Sirt2 failed to affect the disease course, but also did not modify α-tubulin acetylation. These findings show that Hdac6, rather than Sirt2, is a therapeutic target for the treatment of ALS. Moreover, Sirt2 appears not to be a major α-tubulin deacetylase in the nervous syste

Hdac6 deletion delays disease progression in the SOD1(G93A) mouse model of ALS

Defects in axonal transport are thought to contribute to the pathogenesis of neurodegenerative disease. Because -tubulin acetylation facilitates axonal transport, inhibition of the -tubulin deacetylating enzymes, histone deacetylase 6 (Hdac6) and silent information regulator 2 (Sirt2), is thought to be an interesting therapeutic strategy for these conditions. Amyotrophic lateral sclerosis (ALS) is a one such rapidly progressive and fatal neurodegenerative disorder, in which axonal transport defects have been found in vitro and in vivo. To establish whether the inhibition of Hdac6 or Sirt2 may be of interest for ALS treatment, we investigated whether deleting Hdac6 or Sirt2 from the superoxide dismutase 1, SOD1(G93A) mouse affects the motor neuron degeneration in this ALS model. Deletion of Hdac6 significantly extended the survival of SOD1(G93A) mice without affecting disease onset, and maintained motor axon integrity. This protective effect was associated with increased -tubulin acetylation. Deletion of Sirt2 failed to affect the disease course, but also did not modify -tubulin acetylation. These findings show that Hdac6, rather than Sirt2, is a therapeutic target for the treatment of ALS. Moreover, Sirt2 appears not to be a major -tubulin deacetylase in the nervous system

CRISPR/Cas9 screen in human iPSC‐derived cortical neurons identifies NEK6 as a novel disease modifier of C9orf72 poly(PR) toxicity

Introduction The most common genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are hexanucleotide repeats in chromosome 9 open reading frame 72 (C9orf72). These repeats produce dipeptide repeat proteins with poly(PR) being the most toxic one. Methods We performed a kinome-wide CRISPR/Cas9 knock-out screen in human induced pluripotent stem cell (iPSC) -derived cortical neurons to identify modifiers of poly(PR) toxicity, and validated the role of candidate modifiers using in vitro, in vivo, and ex-vivo studies. Results Knock-down of NIMA-related kinase 6 (NEK6) prevented neuronal toxicity caused by poly(PR). Knock-down of nek6 also ameliorated the poly(PR)-induced axonopathy in zebrafish and NEK6 was aberrantly expressed in C9orf72 patients. Suppression of NEK6 expression and NEK6 activity inhibition rescued axonal transport defects in cortical neurons from C9orf72 patient iPSCs, at least partially by reversing p53-related DNA damage. Discussion We identified NEK6, which regulates poly(PR)-mediated p53-related DNA damage, as a novel therapeutic target for C9orf72 FTD/ALS

A genome-wide RNAi screen in mouse embryonic stem cells identifies Mp1 as a key mediator of differentiation

Knockdown of the scaffolding protein Mek binding protein 1 (Mp1) in mouse embryonic stem cells suppresses differentiation but not proliferation, and more invasive human germ cell tumors express lower amounts of Mp1

The adult pituitary contains a cell population displaying stem/progenitor cell and early embryonic characteristics

A side population (SP) has been identified in a number of tissues, where it typically represents a small population enriched in stem/progenitor cells. In this study we show that the adult mouse anterior pituitary (AP) also contains a characteristic SP displaying verapamil-sensitive Hoechst dye efflux capacity. A majority of the SP cells express stem cell antigen 1 at a high level (Sca1high). Using (semi)quantitative RT-PCR and immunofluorescence, we characterized the Sca1high SP as a population enriched in cells expressing stem/progenitor cell-associated factors and components of the Notch, Wnt, and sonic hedgehog signaling pathways, functional in stem cell homeostasis as well as in early pituitary embryogenesis. Lhx4, a transcription factor pivotal for early embryonic development of the AP, was only detected in the Sca1high SP, whereas Lhx3, in contrast to Lhx4 not down-regulated after AP development, was only found in the main population. The Sca1high SP was depleted from cells expressing phenotypic markers of differentiated AP cells (hormones), but contained a small proportion of folliculo-stellate cells. Stem cells of many tissues can clonally expand to nonadherent spheres in culture. Clonal spheres also developed in AP cell cultures. Spheres showed an expression pattern resembling that of Sca1high SP cells. Moreover, the sphere-initiating cells of the pituitary segregated to the SP and not to the main population. In conclusion, we show that the adult pituitary contains a hitherto undescribed population of cells with SP phenotype and clonal expansion capacity. These cells express (signaling) molecules generally found in stem/progenitor cells and/or operative during pituitary early embryonic development. These characteristics are supportive of a stem/progenitor cell phenotype.status: publishe

VEGF protects motor neurons against excitotoxicity by upregulation of GluR2

Influx of Ca(2+) ions through the alpha-amino-3-hydroxy-5-methylisoxazole propionic acid (AMPA) receptors is toxic to neurons and contributes to motor neuron degeneration observed in amyotrophic lateral sclerosis (ALS). The Ca(2+) permeability of the AMPA receptor depends on its subunit composition. If the GluR2 subunit is present in the receptor complex, the AMPA receptor is impermeable to Ca(2+). In this study, we identified vascular endothelial growth factor-A (VEGF) as a GluR2 inducing molecule. Cultured motor neurons pretreated with VEGF displayed higher GluR2 levels. This resulted in AMPA receptor currents with a low relative Ca(2+) permeability and in motor neurons that were less vulnerable to AMPA receptor-mediated excitotoxicity. This effect of VEGF was mediated through the VEGFR2 present on the motor neurons and was due to stimulation of GluR2 transcription. Intracerebroventricular treatment with VEGF similarly induced GluR2 expression in the ventral spinal cord of rats and this mechanism contributes to the protective effect of VEGF on motor neurons.status: publishe

A zebrafish model for C9orf72 ALS reveals RNA toxicity as a pathogenic mechanism

The exact mechanism underlying amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) associated with the GGGGCC repeat expansion in C9orf72 is still unclear. Two gain-of-function mechanisms are possible: repeat RNA toxicity and dipeptide repeat protein (DPR) toxicity. We here dissected both possibilities using a zebrafish model for ALS. Expression of two DPRs, glycine-arginine and proline-arginine, induced a motor axonopathy. Similarly, expanded sense and antisense repeat RNA also induced a motor axonopathy and formed mainly cytoplasmic RNA foci. However, DPRs were not detected in these conditions. Moreover, stop codon-interrupted repeat RNA still induced a motor axonopathy and a synergistic role of low levels of DPRs was excluded. Altogether, these results show that repeat RNA toxicity is independent of DPR formation. This RNA toxicity, but not the DPR toxicity, was attenuated by the RNA-binding protein Pur-alpha and the autophagy-related protein p62. Our findings demonstrate that RNA toxicity, independent of DPR toxicity, can contribute to the pathogenesis of C9orf72-associated ALS/FTD