Dysmyelinogenesis in animal model of GM1 gangliosidosis.
ABSTRACT Magnetic resonance imaging (MRI), pathologic examinations, and biochemical analyses were performed on 2 different canine mutants with GM1 gangliosidosis (i.e., English Springer Spaniel and Portuguese Water Dog) and on age- and sex-matched controls. Serial MRI studies were also performed on a child with infantile-onset GM1 gangliosidosis. The affected dogs had abnormalities on MRI, including a relative increase in gray matter and an abnormal signal intensity of cerebral and cerebellar white matter observed on T2-weighted MRI. White matter changes on MRI were similar to white matter abnormalities observed in a 15-month-old boy with GM1 gangliosidosis. The weight ratio of white to gray matter from the frontal lobe was markedly reduced. Microscopic examination revealed characteristic ballooned neurons which stained lightly with Luxol-fast blue. The central cerebral and cerebellar folia white matter exhibited pallor and gliosis, while the corpus callosum and fornix stained normally with Luxol-fast blue. Axons appeared intact on Bodian staining. Ultrastructural studies revealed fewer myelinated axons in affected puppies. Total gangliosides in gray matter were elevated. Thin-layer chromatography demonstrated GM1 ganglioside as the predominant ganglioside. The amount of cerebrosides and sulfatides was reduced in the gray and white matter when compared to controls but the ratio in gray and white matter remained unchanged. Immunostaining of neutral glycolipids disclosed increased amounts of stage-specific embryonic antigen-1 glycolipid in gray matter. These findings suggest that canine models for GM1 gangliosidosis are associated with abnormal myelin development which may be similar to the human disease.
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ABSTRACT: OBJECTIVE. We set out to determine functional white matter (WM) connections passing through the canine corpus callosum; these WM connections would be useful for subsequent studies of canine brains that serve as models for human WM pathway disease. Based on prior studies, we anticipated that the anterior corpus callosum would send projections to the anterior cerebral cortex whereas progressively posterior segments would send projections to more posterior cortex. MATERIALS AND METHODS. A postmortem canine brain was imaged using a 7-T MRI system producing 100-μm-isotropic-resolution diffusion-tensor imaging analyzed by tractography. Using regions of interest (ROIs) within cortical locations, which were confirmed by a Nissl stain that identified distinct cortical architecture, we successfully identified six important WM pathways. We also compared fractional anisotropy (FA), apparent diffusion coefficient (ADC), radial diffusivity, and axial diffusivity in tracts passing through the genu and splenium. RESULTS. Callosal fibers were organized on the basis of cortical destination (e.g., fibers from the genu project to the frontal cortex). Histologic results identified the motor cortex on the basis of cytoarchitectonic criteria that allowed placement of ROIs to discriminate between frontal and parietal lobes. We also identified cytoarchitecture typical of the orbital frontal, anterior frontal, and occipital regions and placed ROIs accordingly. FA, ADC, radial diffusivity, and axial diffusivity values were all higher in posterior corpus callosum fiber tracts. CONCLUSION. Using six cortical ROIs, we identified six major WM tracts that reflect major functional divisions of the cerebral hemispheres, and we derived quantitative values that can be used for study of canine models of human WM pathologic states.American Journal of Roentgenology 01/2014; 202(1):W19-25. · 2.90 Impact Factor
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ABSTRACT: GM1-gangliosidosis is a rare progressive neurodegenerative disorder due to an autosomal recessively inherited deficiency of lysosomal β-galactosidase. We have identified seven American Black Bears (Ursus americanus) found in the Northeast United States suffering from GM1-gangliosidosis. This report describes the clinical features, brain MRI, morphologic, biochemical and molecular genetic findings in the affected bears. Brain lipids were compared with those in the brain of the GM1-mouse. The bears presented at ages 10 – 14 months in poor clinical condition, lethargic, tremulous and ataxic. They continued to decline and were humanely euthanized. The T2-weighted MR images of the brain of one bear disclosed white matter hyperintensity. Morphological studies of brain from five of the bears revealed enlarged neurons with foamy cytoplasm containing granules. Axonal spheroids were present in white matter. Electron microscopic examination revealed lamellated membrane structures within neurons. Cytoplasmic vacuoles were found in the liver, kidneys and chondrocytes and foamy macrophages within the lungs. Acid β-galactosidase activity in cultured skin fibroblasts was only 1–2 percent of control values. In brain, ganglioside-bound sialic acid was increased more than 2-fold with GM1-ganglioside predominating. GA1 content was also increased whereas cerebrosides and sulfatides were markedly decreased. The distribution of gangliosides was similar to that in GM1-mouse brain, but the loss of myelin lipids was greater in the brain of the affected bear than in the brain of the GM1 mouse. Isolated full-length cDNA of the black bear GLB1 gene revealed 86% homology to its human counterpart in nucleotide sequence and 82% in amino acid sequence. GLB1 cDNA from liver tissue of an affected bear contained a homozygous recessive T1042 to C transition inducing a Tyr348 to His mutation (Y348H) within a highly conserved region of the GLB1 gene. The coincidence of several Black Bears with GM1-gangliosidosis in the same geographic area suggests increased frequency of a founder mutation in this animal population.Molecular Genetics and Metabolism 01/2014; · 2.83 Impact Factor
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ABSTRACT: The sphingolipidoses are a group of inherited lysosomal storage diseases in which sphingolipids accumulate due to the defective activity of one or other of the enzymes involved in their degradation. For most of the sphingolipidoses, little is known about the molecular mechanisms that lead to disease, which has negatively impacted attempts to develop therapies for these devastating human diseases. Use of both genetically-modified animals, ranging from mice to larger mammals, and of novel cell culture systems, is of utmost importance in delineating the molecular mechanisms that cause pathophysiology, and in providing tools that enable testing the efficacy of new therapies. In this review, we discuss eight sphingolipidoses, namely Gaucher disease, Fabry disease, Metachromatic leukodystrophy, Krabbe disease, Niemann-Pick diseases A and B, Farber disease, GM1 gangliosidoses, and GM2 gangliosidoses, and describe the tools that are currently available for their study. This article is part of a Special Issue entitled Tools to study lipid functions.Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids 01/2014; · 4.13 Impact Factor