Deep morphological analysis of muscle biopsies from type III glycogenesis (GSDIII), debranching enzyme deficiency, revealed stereotyped vacuolar myopathy and autophagy impairment.

Glycogen storage disorder type III (GSDIII), or debranching enzyme (GDE) deficiency, is a rare metabolic disorder characterized by variable liver, cardiac, and skeletal muscle involvement. GSDIII manifests with liver symptoms in infancy and muscle involvement during early adulthood. Muscle biopsy is mainly performed in patients diagnosed in adulthood, as routine diagnosis relies on blood or liver GDE analysis, followed by AGL gene sequencing.

Lack of muscle mTOR kinase activity causes early onset myopathy and compromises whole-body homeostasis.

Background: The protein kinase mechanistic target of rapamycin (mTOR) controls cellular growth and metabolism. Although balanced mTOR signalling is required for proper muscle homeostasis, partial mTOR inhibition by rapamycin has beneficial effects on various muscle disorders and age-related pathologies. Besides, more potent mTOR inhibitors targeting mTOR catalytic activity have been developed and are in clinical trials.

Prestressed cells are prone to cytoskeleton failures under localized shear strain: an experimental demonstration on muscle precursor cells.

We report on a wavelet based space-scale decomposition method for analyzing the response of living muscle precursor cells (C2C12 myoblasts and myotubes) upon sharp indentation with an AFM cantilever and quantifying their aptitude to sustain such a local shear strain. Beyond global mechanical parameters which are currently used as markers of cell contractility, we emphasize the necessity of characterizing more closely the local fluctuations of the shear relaxation modulus as they carry important clues about the mechanisms of cytoskeleton strain release. Rupture events encountered during fixed velocity shear strain are interpreted as local disruptions of the actin cytoskeleton structures, the strongest (brittle) ones being produced by the tighter and stiffer stress fibers or actin agglomerates.

Identification of protein features encoded by alternative exons using Exon Ontology.

Transcriptomic genome-wide analyses demonstrate massive variation of alternative splicing in many physiological and pathological situations. One major challenge is now to establish the biological contribution of alternative splicing variation in physiological- or pathological-associated cellular phenotypes. Toward this end, we developed a computational approach, named "Exon Ontology," based on terms corresponding to well-characterized protein features organized in an ontology tree.

LSD1 Controls Timely MyoD Expression via MyoD Core Enhancer Transcription.

MyoD is a master regulator of myogenesis. Chromatin modifications required to trigger MyoD expression are still poorly described. Here, we demonstrate that the histone demethylase LSD1/KDM1a is recruited on the MyoD core enhancer upon muscle differentiation.

Phosphorylation of NBR1 by GSK3 modulates protein aggregation.

The autophagy receptor NBR1 (neighbor of BRCA1 gene 1) binds UB/ubiquitin and the autophagosome-conjugated MAP1LC3/LC3 (microtubule-associated protein 1 light chain 3) proteins, thereby ensuring ubiquitinated protein degradation. Numerous neurodegenerative and neuromuscular diseases are associated with inappropriate aggregation of ubiquitinated proteins and GSK3 (glycogen synthase kinase 3) activity is involved in several of these proteinopathies. Here we show that NBR1 is a substrate of GSK3.

A mutation causes MuSK reduced sensitivity to agrin and congenital myasthenia.

Congenital myasthenic syndromes (CMSs) are a heterogeneous group of genetic disorders affecting neuromuscular transmission. The agrin/muscle-specific kinase (MuSK) pathway is critical for proper development and maintenance of the neuromuscular junction (NMJ). We report here an Iranian patient in whom CMS was diagnosed since he presented with congenital and fluctuating bilateral symmetric ptosis, upward gaze palsy and slowly progressive muscle weakness leading to loss of ambulation.

Interactome mapping of the phosphatidylinositol 3-kinase-mammalian target of rapamycin pathway identifies deformed epidermal autoregulatory factor-1 as a new glycogen synthase kinase-3 interactor.

The phosphatidylinositol 3-kinase-mammalian target of rapamycin (PI3K-mTOR) pathway plays pivotal roles in cell survival, growth, and proliferation downstream of growth factors. Its perturbations are associated with cancer progression, type 2 diabetes, and neurological disorders. To better understand the mechanisms of action and regulation of this pathway, we initiated a large scale yeast two-hybrid screen for 33 components of the PI3K-mTOR pathway.

Identification of an agrin mutation that causes congenital myasthenia and affects synapse function.

We report the case of a congenital myasthenic syndrome due to a mutation in AGRN, the gene encoding agrin, an extracellular matrix molecule released by the nerve and critical for formation of the neuromuscular junction. Gene analysis identified a homozygous missense mutation, c.5125G>C, leading to the p.

Evolution of the global internal dynamics of a living cell nucleus during interphase.

Progress in cellular biology based on fluorescent microscopy techniques, shows that the spatial organization of the nucleus is dynamic. This dynamic is very complex and involves a multitude of phenomena that occur on very different time and size scales. Using an original light scattering experimental device, we investigated the global internal dynamics of the nucleus of a living cell according to the phases of the cell cycle.

Internal dynamics of a living cell nucleus investigated by dynamic light scattering.

Recent progresses in cellular biology have shown that the nucleus of a living cell is a structured integration of many functional domains with a complex spatial organization. This organization, as well as molecular and biochemical processes, is time regulated. In the past years many investigations have been performed using fluorescent microscopy techniques to study the internal dynamics of the nucleus of a living cell.

Towards the molecular elucidation of congenital myasthenic syndromes: identification of mutations in MuSK.

Congenital myasthenic syndromes (CMS) are rare genetic diseases affecting the neuromuscular junction (NMJ) and characterized by a dysfunction of the neurotransmission. They are heterogeneous at the pathophysiological level and can be classified in three categories according to their origin: presynaptic, synaptic or postsynaptic. The strategy for the diagnosis and characterization of CMS relies on the clinic, EMG, muscle biopsy, identification of mutations in genes known to be responsible for CMS and the demonstration that the gene mutations are the cause of the disease by using experimental approaches.

[Pathophysiological characterization of congenital myasthenic syndromes: the example of mutations in the MUSK gene].

Congenital myasthenic syndromes (CMS) are rare genetic diseases affecting the neuromuscular junction (NMJ) and are characterized by a dysfunction of the neurotransmission. They are heterogeneous at their pathophysiological level and can be classified in three categories according to their presynaptic, synaptic and postsynaptic origins. We report here the first case of a human neuromuscular transmission dysfunction due to mutations in the gene encoding a postsynaptic molecule, the muscle-specific receptor tyrosine kinase (MuSK).

MUSK, a new target for mutations causing congenital myasthenic syndrome.

We report the first case of a human neuromuscular transmission dysfunction due to mutations in the gene encoding the muscle-specific receptor tyrosine kinase (MuSK). Gene analysis identified two heteroallelic mutations, a frameshift mutation (c.220insC) and a missense mutation (V790M).

Role for the pleckstrin homology domain-containing protein CKIP-1 in phosphatidylinositol 3-kinase-regulated muscle differentiation.

In this work, we report the implication of the pleckstrin homology (PH) domain-containing protein CKIP-1 in phosphatidylinositol 3-kinase (PI3-K)-regulated muscle differentiation. CKIP-1 is upregulated during muscle differentiation in C2C12 cells. We show that CKIP-1 binds to phosphatidylinositol 3-phosphate through its PH domain and localizes to the plasma membrane in a PI3-K-dependent manner.

Mitogen-activated protein kinase-mediated Fas apoptotic signaling pathway.

Ligation of the cell surface receptor Fas/APO-1 (CD95) by its specific ligand or by anti-Fas antibodies rapidly induces apoptosis in susceptible cells. To characterize the molecular events involved in Fas-induced apoptosis, we examined the contribution of two subgroups of the mitogen-activated protein (MAP) kinase family, the Jun kinases or stress-activated protein kinases (JNKs/SAPKs) and the extracellular signal-regulated kinases (ERKs), in a Fas-sensitive neuroblastoma cell line. Here we show that both JNK and ERK protein kinases were activated upon Fas crosslinking through a Ras-dependent mechanism.

Tumor induction and tissue atrophy in mice lacking E2F-1.

The retinoblastoma tumor suppressor protein (pRB) is a transcriptional repressor that regulates gene expression by physically associating with transcription factors such as E2F family members. Although pRB and its upstream regulators are commonly mutated in human cancer, the physiological role of the pRB-E2F pathway is unknown. To address the function of E2F-1 and pRB/E2F-1 complexes in vivo, we have produced mice homozygous for a nonfunctional E2F-1 allele.

IL-10 inhibits alloreactive cytotoxic T lymphocyte generation in vivo.

In this report, we present evidence that the CTL response directed against MHC Class I allo-determinants can be inhibited as a result of IL-10 expression in vivo. The presence of localized IL-10 secretion at the site of allogeneic tumor cell challenge resulted in marked inhibition of the CTL response and allowed growth of the tumor in the allogeneic host. Using purified CD4+ T cells from mice immunized in the presence or absence of IL-10, we have shown that the loss of alloreactivity as a consequence of IL-10 expression results from the inhibition of CD4+ T cell function.

Serum level of interleukin 6 as a prognosis factor in metastatic renal cell carcinoma.

Interleukin (IL) 6 was measured in the serum of 138 patients with metastatic renal carcinoma before the initiation of IL-2 treatment. IL-6 was detectable in 66 patients with renal cancer (48%) and in only 8 of 70 normal adults (11%). Serum C reactive protein (CRP) and IL-6 levels are correlated, suggesting that IL-6 is involved in CRP increase in these patients.

Tumor necrosis factor as an autocrine growth factor for neuroblastoma.

Recombinant tumor necrosis factor (TNF) stimulates the proliferation of two neuroblastoma cell lines, SKNFI and SKNBE, in both serum-free medium and fetal calf serum-supplemented medium but has no effect in medium without insulin. This effect is very similar with TNF doses ranging from 5 to 500 ng/ml but depends on the duration of treatment; when cells are treated for 168 h with TNF, the maximal index of proliferation is observed between 120 and 144 h of treatment. The two neuroblastoma cell lines express type A and type B TNF receptors and contain TNF protein; however, TNF is undetectable in culture supernatants.

Fetal liver cell transplantation in various murine models.

Allogeneic fetal liver cell transplantation has been shown to be able to reconstitute lymphopoietic systems of mice when these systems are defective or destroyed. Lethally irradiated mice or mice with inherited severe combined immunodeficiency disease (SCID) were grafted with 14 days gestation allogeneic fetal liver cells, then subjected to a follow-up for the immune tolerance to the donor and the normal or subnormal immune reconstitution allowing prevention of diabetes in NOD mice or cure of leukemia in AKR mice and of immunodeficiency in SCID mice. Briefly, when normal CBA mice were lethally irradiated and then grafted with allogeneic fetal liver cells from Balb/c mice, a specific immune tolerance was induced to donor skin grafts.

Expression of integrin receptors on 45 clinical neuroblastoma specimens.

Immunohistological expression of integrins has been analyzed on 45 neuroblastoma specimens representative of the different clinical and histological forms of the tumor. None of the specimens expressed the alpha 5 chain of the integrins. The beta 1 chain was expressed on all specimens, the alpha 1 chain on 44 specimens and the alpha 3 chain on 42; the 4 specimens which lacked alpha 1 or alpha 3 were stage-4 neuroblastomas.