Bone marrow transplantation for lysosomal diseases.
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Animals↗
Biomedical subjects
S U Walkley
Publications and source records attributed to S U Walkley.
GM2 ganglioside and pyramidal neuron dendritogenesis.
GM2 ganglioside, although scarce in normal adult brain, is the predominant ganglioside accumulating in several types of lysosomal disorders, most notably Tay-Sachs disease. Pyramidal neurons of cerebral cortex in Tay-Sachs, as well as many other types of neuronal storage disorders, are known to exhibit a phenomenon believed unique to storage disorders: growth of ectopic dendrites. Recent studies have shown that a common metabolic abnormality shared by storage diseases with ectopic dendrite growth is the abnormal accumulation of GM2 ganglioside. The correlation between increased levels of GM2 and the presence of ectopic dendrites has been found in both ganglioside and nonganglioside storage disorders, the latter including sphingomyelin-cholesterol lipidosis, mucopolysaccharidosis, and alpha-mannosidosis. Quantitative HPTLC analysis has shown that increases in GM2 occur in proportion to the incidence of ectopic dendrite growth, whereas other gangliosides, including GM1, lack similar increases. Immunocytochemical studies of all nonganglioside storage diseases which exhibit ectopic dendritogenesis have revealed heightened GM2 ganglioside-immunoreactivity in the cortical pyramidal cell population, whereas nerurons in normal adult brain exhibit little or no staining for this ganglioside. Further, studies examining disease development have consistently shown that accumulation of GM2 ganglioside precedes growth of ectopic dendrites, indicating that it is not simply occurring secondary to new membrane production. These findings have prompted an examination for a similar relationship between GM2 ganglioside and dendritogenesis in cortical neurons of normal developing brain. Results show that GM2 ganglioside-immunoreactivity is consistently elevated in immature neurons during the period when they are undergoing active dendritic initiation, but this staining diminishes dramatically as the dendritic trees of these cells mature. Collectively, these studies on diseased and normal brain offer compelling evidence that GM2 ganglioside plays a pivotal role in the regulation of dendritogenesis in cortical pyramidal neurons.
Adult↗
Pyramidal neurons with ectopic dendrites in storage diseases exhibit increased GM2 ganglioside immunoreactivity.
Cortical pyramidal neurons in several types of neuronal storage diseases have been shown by Golgi staining to sprout axon hillock-associated dendritic processes. Based on the relative incidence of this ectopic dendritogenesis, and on quantitative analyses of gangliosides in these same tissues, it has been proposed that abnormal accumulation of a specific metabolic product, GM2 ganglioside, is the pivotal event leading to re-initiation of dendritic sprouting [Siegel D. A. Walkley S.U. (1994) J. Neurochem. 62, 1852-1862]. In the present study, a monoclonal antibody was used to determine the cellular location of this ganglioside within the cerebral cortex of animal models of storage diseases with and without ectopic dendrite growth. Diseases exhibiting ectopic dendritogenesis included inherited and swainsonine-induced (juvenile-onset) alpha-mannosidosis, mucopolysaccharidosis type I, Niemann-Pick disease type C, and GM1 and GM2 gangliosidosis. Conditions lacking ectopic dendrite growth included adult-onset swainsonine-induced alpha-mannosidosis, fucosidosis, neuronal ceroid lipofuscinosis (Batten disease) and normal, mature brain. Immunocytochemical staining for GM2 ganglioside indicated that diseases exhibiting new dendritic sprouting with the exception of GM1 gangliosidosis, exhibited abundant GM2-like immunoreactivity within the cortical pyramidal cell population, whereas diseases without dendritic sprouting had GM2-like immunoreactivity limited to glia and/or to non-pyramidal neurons. Cortical tissues from normal animals at comparable ages and processed by similar procedures exhibited occasional glial cell staining but little or no neuronal labelling. Mechanisms by which normal cortical pyramidal regulate dendritic initiation are poorly understood. However, it is known that this event is developmentally restricted, occurring only during early brain development.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Bone marrow transplantation corrects the enzyme defect in neurons of the central nervous system in a lysosomal storage disease.
Neuronal storage disorders are fatal neurodegenerative diseases of humans and animals that are caused by inherited deficiencies of lysosomal hydrolase activity. Affected individuals often appear normal at birth but eventually develop progressive neurologic symptoms including sensory and motor deficits, mental retardation, and seizures. We have examined efficacy of bone marrow transplantation as a means of enzyme replacement, using cats with the lysosomal storage disease alpha-mannosidosis. Treated animals showed little or no progression of neurologic signs 1-2 years after transplant, whereas untreated cats became severely impaired and reached endstage disease by 6 months of age. Increased lysosomal alpha-mannosidase activity was found in brain tissue of the treated animals, and electron microscopy revealed no evidence of lysosomal storage within most neurons. Histochemical localization of acidic alpha-D-mannoside mannohydrolase (EC 3.2. 1.24), using 5-bromo-4-chloro-3-indolyl alpha-D-mannopyranoside, showed that functional enzyme was present in neurons, glial cells, and cells associated with blood vessels. This study provides direct evidence that bone marrow transplantation as treatment for a neuronal storage disease can lead to significant levels of a missing lysosomal hydrolase within neurons of the central nervous system and to compensation for the genetic metabolic defect.
Animals↗
Growth of ectopic dendrites on cortical pyramidal neurons in neuronal storage diseases correlates with abnormal accumulation of GM2 ganglioside.
Ganglioside analysis and quantitative Golgi studies of the cerebral cortex of cats with ganglioside and nonganglioside lysosomal storage diseases reveal a correlation between the amount of accumulated GM2 ganglioside and the extent of ectopic dendrite growth on cortical pyramidal neurons. This correlation was not observed with any of the other gangliosides assayed for, including GM1 ganglioside. These results suggest a specific role for GM2 ganglioside in the initiation of ectopic neurites on pyramidal cells in vivo and are consistent with the developing hypothesis that different gangliosides have specific roles in different cell types dependent upon the receptor or other effector molecules with which they may interact.
Aging↗
Feline Niemann-Pick disease type C.
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Alanine Transaminase↗
Biology of neuronal dysfunction in storage disorders.
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Animals↗
Ectopic dendrites occur only on cortical pyramidal cells containing elevated GM2 ganglioside in alpha-mannosidosis.
In a variety of neuronal storage diseases, cortical pyramidal cells elaborate ectopic dendrites at the axon hillock. A feature common to all the diseases characterized by ectopic dendrites is an elevated level of GM2 ganglioside in cerebral cortex. In cats with one such disease, alpha-mannosidosis, the number of pyramidal cells bearing ectopic dendrites is small; the present study shows that GM2 ganglioside is stored only in those pyramidal neurons exhibiting ectopic dendrites. Using a Golgi-electron microscopy method with periodic acid-Schiff (PAS) staining, we first established that pyramidal cells bearing ectopic dendrites contained PAS+ membranous inclusions, consistent with storage of glycolipids. In contrast, those with smooth axon hillocks accumulated PAS- floccular inclusions, consistent with storage of oligosaccharides. Next, application of a monoclonal antibody against GM2 ganglioside revealed that subsets of both pyramidal and intrinsic neurons contained GM2-like immunoreactivity. Every GM2+ cell contained PAS+ membranous inclusions, indicating that pyramidal cells bearing ectopic dendrites stored GM2 ganglioside. In cats with alpha-mannosidosis induced by swainsonine, some pyramidal neurons showed GM2-like immunoreactivity after 4 weeks of treatment, whereas ectopic dendrites only became evident after 7 weeks of treatment. Thus, GM2 ganglioside accumulated in pyramidal neurons before ectopic dendrites emerged from the axon hillock. We propose that the reinitiation of dendrite growth on mature pyramidal cells is brought about by accumulated GM2 ganglioside.
Animals↗
Neuroaxonal dystrophy in neuronal storage disorders: evidence for major GABAergic neuron involvement.
The formation of focal granular enlargements within axons (axonal spheroids or "torpedoes"; neuroaxonal dystrophy) is a well known phenomenon occurring in a variety of neurological diseases. The relative susceptibility of different types of neurons to this kind of axonal pathology, however, is largely unknown. An immunocytochemical study directed at localizing glutamic acid decarboxylase (GAD), the synthetic enzyme for the inhibitory neurotransmitter, gamma-aminobutyric acid (GABA), in various CNS regions in feline models of lysosomal storage disorders has revealed vast numbers of axonal spheroids containing this enzyme. In some storage diseases (GM1 and GM2 gangliosidosis), GAD-immunoreactive spheroids were a common occurrence in many brain regions, whereas in other disorders these structures were more limited in distribution (alpha-mannosidosis), or were absent (mucopolysaccharidosis type I). Axonal spheroids unreactive for GAD were encountered in large numbers in subcortical white matter in GM2 gangliosidosis, but were infrequently observed in the other diseases. The incidence and distribution of GAD-immunoreactive spheroids in the various diseases under study were found to correlate closely with the type and degree of neurological deficits exhibited by affected animals. This study indicates that the neuroaxonal dystrophy occurring in some types of storage disorders commonly involves axons of GABAergic neurons and suggests that a resulting defect in neurotransmission in inhibitory circuits may be an important factor underlying brain dysfunction in this family of diseases.
Animals↗
Distribution of ectopic neurite growth and other geometrical distortions of CNS neurons in feline GM2 gangliosidosis.
Golgi and combined Golgi-electron microscopic (EM) studies were carried out on cats in the terminal stages of GM2 ganglioside storage disease and the resulting data were compared with those from similar studies of other neuronal storage diseases in cats, including GM1 gangliosidosis. The results support the view that only limited types of neurons affected by the lysosomal hydrolase deficiency and subsequent intracellular storage have the capacity to sprout new dendritic-like growth processes from their axon hillocks, and that these neurons are essentially the same in all of these diseases studied to date. Golgi studies of CNS tissues from GM2 gangliosidosis cats revealed ectopic neurite growth on pyramidal neurons of cerebral cortex and multipolar cells of amygdala and claustrum, whereas other types of neurons responded to the metabolic defect with aspiny meganeurite formation or somatic enlargement, or appeared normal in terms of soma-dendritic morphology. Combined Golgi-EM studies of cortical pyramidal neurons revealed that ectopic, axon hillock neurites commonly possessed asymmetrical synapses which were similar to those observed in other storage disorders.
Animals↗
Initiation and growth of ectopic neurites and meganeurites during postnatal cortical development in ganglioside storage disease.
The incidence of cortical pyramidal neurons displaying meganeurites or enlarged axon hillocks with ectopic spines and neurites was evaluated developmentally using feline models of GM1 and GM2 gangliosidosis. Results of these studies demonstrated that the onset of ectopic neurite growth occurred after the elaboration of dendrites on cortical pyramidal neurons, and that the time of onset of this renewed dendritogenesis was similar in the two diseases. Initiation and growth of ectopic neurites also correlated in a general way with onset and progression of clinical deterioration in both diseases. In GM1 gangliosidosis there was a greater tendency toward formation of meganeurites, whereas in cats with GM2 gangliosidosis the growth of ectopic axon hillock neurites without meganeurites predominated. At end-stage disease in GM2 gangliosidosis, nearly 90% of pyramidal cells displayed some degree of axon hillock neurite growth as opposed to less than half this number for GM1 gangliosidosis cats at the same age. These data are consistent with the hypothesis that there are two separate driving forces behind these somadendritic abnormalities of pyramidal neurons in the gangliosidoses. Excessive intraneuronal accumulation of storage vacuoles accounts for the formation of meganeurites, whereas some type of intrinsic metabolic defect results in axon hillock neurite growth which in turn offers new surface area for synaptic input. Currently available data indicate that GM2 or GM3 ganglioside, or a closely related metabolic product other than GM1 ganglioside, may be primarily associated with the growth of ectopic dendritic processes on morphologically mature neurons in storage diseases.
Animals↗
The effects of gabaculine in vivo on the distribution of GABA-like immunoreactivity in the rat retina.
gamma-Aminobutyric acid (GABA) is an inhibitory transmitter found in the retinae of mammals largely within certain amacrine cells. In previous studies from this laboratory, subcutaneous administration to rats of gabaculine, an enzyme-activated irreversible inhibitor of gamma-aminobutyric acid (GABA)-transaminase, produced large, rapid and long-lasting increases in levels of retinal GABA. We employed immunocytochemistry to determine whether such changes in the levels of retinal GABA are accompanied by changes in the cellular distribution of GABA. Using a recently developed antiserum to a GABA-protein conjugate, and the peroxidase-antiperoxidase method, we examined retinae from control rats and from rats 2 or 8 h after administration of 10 mg/kg gabaculine. From previous work, retinal levels of GABA were respectively elevated 3- or 6-fold at those postgabaculine times. In the present study, marked changes in the distribution of GABA-like immunoreactivity (GABA-LIR) were apparent by 2 h after injection of gabaculine, and were more striking at 8 h postgabaculine. The pattern of staining for GABA-LIR strongly suggested that much of the GABA in gabaculine-treated retinae was within Müller glial cells. That observation provides evidence for the importance of those cells in the uptake and degradation of GABA after its release from retinal neurons.
Animals↗
Inherited lysosomal storage disease associated with deficiencies of beta-galactosidase and alpha-neuraminidase in sheep.
Histopathologic, ultrastructural and Golgi impregnation studies disclosed lesions characteristic of a neuronal lysosomal storage disease in related sheep with onset of neurologic signs at 4-6 months. Biochemical and enzymatic evaluation disclosed storage of GM1 ganglioside, asialo-GM1, and neutral long chain oligosaccharides in brain, urinary excretion of neutral long chain oligosaccharides, and deficiencies of lysosomal beta-galactosidase and alpha-neuraminidase. Retrospective and limited prospective genetic studies suggested autosomal recessive inheritance. A gene-dosage effect on beta-galactosidase levels was documented in fibroblasts from putative heterozygous sheep. Fibroblasts from affected sheep did not have increased beta-galactosidase activity after incubation with the protease inhibitor, leupeptin. In some aspects this disease is similar to GM1 gangliosidosis, but is unique in that a genetic defect in lysosomal beta-galactosidase may cause the deficiency of lysosomal alpha-neuraminidase.
Animals↗
Alterations in neuron morphology in mucopolysaccharidosis type I. A Golgi study.
Morphological changes in neurons with inborn defects of the lysosomal hydrolase, alpha-L-iduronidase, and with concomitant storage of glycosaminoglycans, were evaluated by Golgi staining in two animal models and compared to a similar study of a child with the same disease. Cortical pyramidal neurons in feline mucopolysaccharidosis type I often displayed axon hillock enlargements (meganeurites) and/or ectopic, secondary neuritic processes sprouting from this same region of the cell. The latter structures were prominent and often appeared longer than similar neurites reported in other neuronal storage diseases. Although most meganeurites were aspiny, a few were observed which possessed spine-like processes or neurites. Other than these morphological changes in cortical pyramidal neurons, few other cell types displayed abnormalities demonstrable by Golgi impregnation. In the canine model of this disorder, abnormal Golgi-impregnated cortical neurons resembled more closely those seen in human mucopolysaccharidosis. That is, they possessed meganeurites which typically were aspiny in appearance. Ectopic neurite growth was not observed on any Golgi-impregnated neurons in the cases of canine or human mucopolysaccharidosis used in this study. The latter finding, given the advanced ages of these cases, is consistent with the view that ectopic neuritogenesis seen in neuronal storage diseases may be subject to a developmental window, albeit one open well beyond the period of early postnatal maturation.
Animals↗
Pathobiology of neuronal storage disease.
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Animals↗
Ectopic dendritogenesis and associated synapse formation in swainsonine-induced neuronal storage disease.
Ectopic dendrite growth and new synapse formation are known to occur on select kinds of neurons in a wide variety of neuronal storage diseases. As these changes in connectivity occur just proximal to the axonal initial segment, it has been hypothesized that they underlie the generation of abnormal neuronal function in these diseases. We have studied certain aspects of this phenomenon through the use of a plant-derived indolizadine alkaloid, swainsonine, which specifically inhibits the lysosomal hydrolase, alpha-mannosidase. These studies fully document the close morphological similarity between swainsonine-induced and inherited feline alpha-mannosidosis. This includes the presence of clear and floccule-filled storage vacuoles, as seen with routine EM, and axon hillock neurite growth on select cell types, as seen with Golgi staining. The latter was found only on cortical pyramidal neurons and multipolar cells of amygdala, and these same cell types are known to be involved in ectopic neuritogenesis in other storage diseases. Combined Golgi-electron-microscopic studies demonstrated the presence of normal-appearing synapses on these aberrant neuritic processes and also unusual, membranous inclusions specifically within the neurite-bearing pyramidal cells. The latter may be indicative of unique metabolic changes in these neurons and is consistent with the hypothesis that storage of gangliosides or other glycolipids underlies the recapitulation of dendritic growth features in these diseases. Experimental manipulation of the disease process using the swainsonine model indicated that induction of cortical pyramidal neuron neurite growth could be influenced by both age of onset and intensity of intraneuronal storage. Although Golgi studies clearly demonstrated neuritic sprouting in animals with disease onset as late as at 1 year, cortical pyramidal cells of older, adult animals appeared to undergo significant storage without a similar induction of neurite growth. These studies support the view that induced neuritogenesis in neuronal storage disease is associated with changes in metabolism, specifically within the neurite-bearing cells, that this change possibly involves gangliosides, and that the neuritogenic response may be limited to pre-adult stages of brain maturation.
Alkaloids↗
Ectopic axon hillock-associated neurite growth is maintained in metabolically reversed swainsonine-induced neuronal storage disease.
An experimentally induced and reversible model of a neuronal storage disease, swainsonine-induced feline alpha-mannosidosis, has been used to study the modifiability of ectopic, axon hillock-associated neurites and their new synaptic contacts. Earlier studies have fully documented that a variety of neuronal storage disorders are characterized by such changes in neuronal geometry and connectivity. Swainsonine administration was ended after 6 months of continuous treatment which had resulted in characteristic signs of alpha-mannosidosis. Studies of this animal 6 months after reversal showed that even though neuronal vacuolation and other CNS changes essentially normalized, ectopic neurites and their synaptic connections were still present and appeared similar to those of another animal which had been treated with swainsonine for the entire 12-month period. These results suggest that once initiated during the disease process, ectopic axon hillock-associated dendrites become an integral part of the soma-dendritic domain of affected neurons and may not be reversible. These findings may have relevance for current attempts to devise therapies involving enzyme replacement for individuals with inherited neuronal storage disease.
Alkaloids↗
Further studies on ectopic dendrite growth and other geometrical distortions of neurons in feline GM1 gangliosidosis.
Systematic Golgi studies have been performed on major subcortical, diencephalic, brain stem and spinal cord regions from cats with the inherited neuronal storage disease, GM1 gangliosidosis. Resulting data have been compared with other Golgi studies of neuronal storage disorders in man and animals, including an earlier, more limited examination of this same disease model. These previous studies have shown that in human and feline gangliosidoses cortical pyramidal neurons undergo remarkable changes in soma-dendritic geometry. The latter include the formation of conspicuous cellular enlargements between somata and axonal initial segments (meganeurites) and the sprouting of secondary neuritic processes from this same region of the cell. Further, ultrastructural studies have revealed normal appearing synapses on the surface of this ectopically placed dendritic-like membrane. Results of the present study indicate that the distribution of meganeurites, secondary neurites and other geometrical distortions of neurons in GM1 gangliosidosis varies with cell type and brain region. This cell type-specific response to the metabolic error and subsequent storage could be categorized in three ways. Firstly, certain types of cells (e.g. multipolar neurons of the amygdala and claustrum) exhibited changes similar to those reported for cortical pyramidal neurons. That is, cells of these regions either displayed spine or neurite-bearing meganeurites, or enlarged axon hillocks which were covered with similar processes. Other types of neurons did not demonstrate ectopic neurite growth or spine-covered meganeurites, but did display prominent aspiny meganeurites (e.g. neurons of the superior colliculus, periaqueductal gray, hypothalamus and basal forebrain nuclei). A third category of neurons did not possess meganeurites or neurite growth but instead demonstrated massive somatic expansion which exceeded that observed in meganeurite-bearing cell types (e.g. certain brain stem and spinal cord neurons). These data have been compared with the more limited Golgi studies of other types of neuronal storage disorders and the same types of neurons appeared to respond in similar fashion across this spectrum of diseases. The data presented and discussed in this paper demonstrate three significant morphological events which occur in neurons as a result of lysosomal hydrolase deficiency. These are storage, which occurs in all neurons but manifests as meganeurite formation or somatic enlargement depending on the cell type, axon hillock or meganeurite-associated spine and neurite growth, and new synapse formation on spine-covered meganeurites and on neurites.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗