Glycogenin is Dispensable for Glycogen Synthesis in Human Muscle, and Glycogenin Deficiency Causes Polyglucosan Storage

Glycogenin is considered to be an essential primer for glycogen biosynthesis. Nevertheless, patients with glycogenin-1 deficiency due to biallelic GYG1 (NM_004130.3) mutations can store glycogen in muscle. Glycogenin-2 has been suggested as an alternative primer for glycogen synthesis in patients with glycogenin-1 deficiency. OBJECTIVE: The objective of this article is to investigate the importance of glycogenin-1 and glycogenin-2 for glycogen synthesis in skeletal and cardiac muscle. DESIGN, SETTING, AND PATIENTS: Glycogenin-1 and glycogenin-2 expression was analyzed by Western blot, mass spectrometry, and immunohistochemistry in liver, heart, and skeletal muscle from controls and in skeletal and cardiac muscle from patients with glycogenin-1 deficiency. RESULTS: Glycogenin-1 and glycogenin-2 both were found to be expressed in the liver, but only glycogenin-1 was identified in heart and skeletal muscle from controls. In patients with truncating GYG1 mutations, neither glycogenin-1 nor glycogenin-2 was expressed in skeletal muscle. However, nonfunctional glycogenin-1 but not glycogenin-2 was identified in cardiac muscle from patients with cardiomyopathy due to GYG1 missense mutations. By immunohistochemistry, the mutated glycogenin-1 colocalized with the storage of glycogen and polyglucosan in cardiomyocytes. CONCLUSIONS: Glycogen can be synthesized in the absence of glycogenin, and glycogenin-1 deficiency is not compensated for by upregulation of functional glycogenin-2. Absence of glycogenin-1 leads to the focal accumulation of glycogen and polyglucosan in skeletal muscle fibers. Expression of mutated glycogenin-1 in the heart is deleterious, and it leads to storage of abnormal glycogen and cardiomyopathy

Nodular bilateral amygdala degeneration in demented individuals

Among more than 2050 brains in our Alzheimer disease brain banks we came across three brains with well demarcated indurated white-yellow nodules in the amygdalas. Microscopically, these nodules were composed of numerous lipid-laden macrophages located in the central region surrounded by an eosinophilic hyaline-like material with minimal reactive gliosis in the periphery. Neurons within these lesions had a normal appearance but were moderately decreased in number. Beta-amyloid, tau and alpha-synuclein immunostaining revealed no abnormal deposits within the nodules. The three patients had long histories of dementia (one linked to a presenilin-1 mutation). The neuropathological diagnoses were Alzheimer disease in two of them and an unclassified tauopathy with argyrophilic grains in the third

Glioblastoma on a microfluidic chip: Generating pseudopalisades and enhancing aggressiveness through blood vessel obstruction events

Background: Glioblastoma (GBM) is one of the most lethal tumor types. Hypercellular regions, named pseudo- palisades, are characteristic in these tumors and have been hypothesized to be waves of migrating glioblastoma cells.These “waves” of cells are thought to be induced by oxygen and nutrient depletion caused by tumor-induced blood vessel occlusion. Although the universal presence of these structures in GBM tumors suggests that they may play an instrumental role in GBM’s spread and invasion, the recreation of these structures in vitro has remained challenging. Methods: Here we present a new microfluidic model of GBM that mimics the dynamics of pseudopalisade forma- tion.To do this, we embedded U-251 MG cells within a collagen hydrogel in a custom-designed microfluidic device. By controlling the medium flow through lateral microchannels, we can mimic and control blood-vessel obstruction events associated with this disease. Results: Through the use of this new system, we show that nutrient and oxygen starvation triggers a strong migratory process leading to pseudopalisade generation in vitro.These results validate the hypothesis of pseudo- palisade formation and show an excellent agreement with a systems-biology model based on a hypoxia-driven phenomenon. Conclusions: This paper shows the potential of microfluidic devices as advanced artificial systems capable of mod- eling in vivo nutrient and oxygen gradients during tumor evolution

Heterozygous and Homozygous Variants in SORL1 Gene in Alzheimer's Disease Patients: Clinical, Neuroimaging and Neuropathological Findings

In the last few years, the SORL1 gene has been strongly implicated in the development of Alzheimer’s disease (AD). We performed whole-exome sequencing on 37 patients with early-onset dementia or family history suggestive of autosomal dominant dementia. Data analysis was based on a custom panel that included 46 genes related to AD and dementia. SORL1 variants were present in a high proportion of patients with candidate variants (15%, 3/20). We expand the clinical manifestations associated with the SORL1 gene by reporting detailed clinical and neuroimaging findings of six unrelated patients with AD and SORL1 mutations. We also present for the first time a patient with the homozygous truncating variant c.364C>T (p.R122*) in SORL1, who also had severe cerebral amyloid angiopathy. Furthermore, we report neuropathological findings and immunochemistry assays from one patient with the splicing variant c.4519+5G>A in the SORL1 gene, in which AD was confirmed by neuropathological examination. Our results highlight the heterogeneity of clinical presentation and familial dementia background of SORL1-associated AD and suggest that SORL1 might be contributing to AD development as a risk factor gene rather than as a major autosomal dominant gene.This work was supported by the Instituto de Salud Carlos III (PI17/01067) and AGAUR from the Autonomous Catalan Government (2017SGR1134). Dr. Víctor Antonio Blanco-Palmero is supported by the Instituto de Salud Carlos III (ISCIII, Spanish Biomedical Research Institute) through a “Río Hortega” contract (CM18/0095). Dr. Sara Llamas-Velasco is supported by the Instituto de Salud Carlos III (ISCIII; Spanish Biomedical Research Institute) through a “Juan Rodés” contract (JR 18/00046).S

De novo RYR1 heterozygous mutation (I4898T) causing lethal core-rod myopathy in twins

"Core-rod myopathy" is a rare congenital myopathy characterized by the presence of "cores" and "rods" in distinct locations in the same or different muscle fibres. This association is linked currently to mutations in RYR1, NEB and ACTA1 genes. We report identical twins who presented with polyhydramnios and loss of fetal motility during pregnancy; hypotonia, arthrogryposis and swallowing impairment at birth; need of immediate respiratory support and death at 27 and 50 days of life. Muscle biopsies, performed at 27 days of life in twin 1 and at 49 days in twin 2, showed the presence of separate cores and rods in the muscle fibres, both at light and electron microscopy. The molecular analysis showed a heterozygous de novo mutation (Ile4898Thr) of the RYR1 gene. The molecular study of ACTA1, TMP2 and TMP3 genes did not show abnormalities. This is the first report of a lethal form of congenital "core-rod myopathy". The mutation Ile4898Thr has been previously described in central core disease but not in core-rod myopathy. The report enlarges the phenotypic spectrum of "core-rod myopathy" and highlights the morphological variability associated to special RYR1 mutations.status: publishe

De novo RYR1 heterozygous mutation (I4898T) causing lethal core-rod myopathy in twins

International audience"Core-rod myopathy" is a rare congenital myopathy characterized by the presence of "cores" and "rods" in distinct locations in the same or different muscle fibres. This association is linked currently to mutations in RYR1, NEB and ACTA1 genes. We report identical twins who presented with polyhydramnios and loss of fetal motility during pregnancy; hypotonia, arthrogryposis and swallowing impairment at birth; need of immediate respiratory support and death at 27 and 50 days of life. Muscle biopsies, performed at 27 days of life in twin 1 and at 49 days in twin 2, showed the presence of separate cores and rods in the muscle fibres, both at light and electron microscopy. The molecular analysis showed a heterozygous de novo mutation (Ile4898Thr) of the RYR1 gene. The molecular study of ACTA1, TMP2 and TMP3 genes did not show abnormalities. This is the first report of a lethal form of congenital "core-rod myopathy". The mutation Ile4898Thr has been previously described in central core disease but not in core-rod myopathy. The report enlarges the phenotypic spectrum of "core-rod myopathy" and highlights the morphological variability associated to special RYR1 mutations

A new muscle glycogen storage disease associated with glycogenin-1 deficiency

International audienceWe describe a slowly progressive myopathy in 7 unrelated adult patients with storage of polyglucosan in muscle fibers. Genetic investigation revealed homozygous or compound heterozygous deleterious variants in the glycogenin-1 gene (GYG1). Most patients showed depletion of glycogenin-1 in skeletal muscle, whereas 1 showed presence of glycogenin-1 lacking the C-terminal that normally binds glycogen synthase. Our results indicate that either depletion of glycogenin-1 or impaired interaction with glycogen synthase underlies this new form of glycogen storage disease that differs from a previously reported patient with GYG1 mutations who showed profound glycogen depletion in skeletal muscle and accumulation of glycogenin-1. Ann Neurol 2014;76:891–89