Margaret Z. Jones

Caprine β-Mannosidosis: Clinical and Pathological Features

Beta-mannosidosis, an inherited defect of glycoprotein catabolism associated with deficiency of tissue β-mannosidase and accumulation of Man(β1–4)GlcNAc and Man(β1–4)GlcNAc(β1–4)GlcNAc, appeared in four of 13 offspring of a single pair of clinically normal, related Nubian goats. Neurological examinations revealed that all four affected goats were unable to rise or walk. All had facial dysmorphism, dome-shaped skulls, small palpebral fissures, carpal contractures, hyperextension of the pastern joints, proximal muscle atrophy, intermittent ocular oscillations resembling pendular nystagmus, marked intention tremor, and deafness. With intensive care, three affected kids were hand-reared and then killed at 1, 7, and 21 days of age. Macroscopically, there were paucity of myelin in the cerebral and cerebellar hemispheres and ventricular dilatation. Microscopically, the extent and distribution of cytoplasmic vacuolation, myelin paucity, axonal spheroids, and filamentous expansions were evaluated in the cerebrum, cerebellum, brainstem, spinal cord, and peripheral nerves of the four affected kids and two age-matched, clinically normal kids. Widespread cytoplasmic vacuolation correlated with the previously reported accumulation of oligosaccharides in the brain and kidney and the deficiency of tissue β-mannosidase. β-Mannosidosis, not yet identified in man or other species, is characterized by distinctive neonatal clinical, pathological and biochemical features which differentiate it from the α-mannosidoses and other inherited diseases of glycoprotein catabolism.

Human mucopolysaccharidosis IIID: clinical, biochemical, morphological and immunohistochemical characteristics

Mucopolysaccharidosis IIID (MPS IIID) is one of the rarest of the MPS-III syndromes. To date, the clinical manifestations of 10 patients have been reported, the deficient N-acetylglucosamine 6-sulfatase (G6S) enzyme has been purified, and the G6S gene has been cloned, sequenced and localized. However, morphological manifestations of this condition have not been reported and the pathogenesis of the severe neurological deficits remains an enigma. In this paper we describe and correlate the clinical, biochemical and pathological observations for 2 cases of MPS IIID. We used monoclonal antibodies against heparan sulfate (HS) and GMZ-ganglioside, thin layer chromatography, mass spectrometry, and morphological techniques to demonstrate the nature and the distribution of the uncatabolized substrates. The majority of the cells in various tissues showed morphological changes expected with lysosomal storage of HS. The central nervous system (CNS) was most severely affected because of the secondary storage of GM2 and GM3 gangliosides in addition to the primary accumulation of HS. The extent as well as the distribution of the diverse storage materials varied within and among different neurons as observed in MPS-III A, B, and C syndromes. This study supports the hypothesis that the neurological dysfunction and neurodegencration common to the Sanfilippo syndromes is, in part, due to the secondary metabolic perturbations induced by HS accumulation.

Pathogenesis of methylazoxymethanol-induced lesions in the postnatal mouse cerebellum.

Previous studies have shown that methylazoxymethanol acetate (MAM) and methylazoxymethanol glucoside (cycasin) cause destruction of differentiating cells in the postnatal mouse cerebellum. The major features of the resulting architectural disarray were Purkinje cell misalignment and granule cell deletion along with cerebellar dysfunction. Although it was clear from a number of studies that destruction of differentiating cells in the immediate postnatal period was the primary lesion, several important facets of the pathogenesis of the lesions remained unexplained. For example, the cellular response to the injury was incompletely described. The relationship of the cellular response to the subsequent pathological alterations was not completely evaluated. Also, the presence of unattached Purkinje cell dendritic spine postsynaptic sites suggested that their development had occurred without presynaptic parallel fiber terminal differentiation. The possibility of early synaptogenesis and degeneration was not, however, completely ruled out. In this study, the early reaction to MAM-induced differentiating cell necrosis and its relationship to the resulting abnormal cerebellar architecture was evaluated. Concomitantly, an attempt was made to clarify whether Purkinje cell postsynaptic sites differentiated with certainty in the absence of parallel fiber contacts or resulted from selective degeneration of previously formed synaptic contacts. As in previous studies, cellular necrosis and a wide range of nuclear and cytoplasmic alterations in the differentiating cells of the cerebellum were demonstrated within forty-eight hours following MAM administration. Many necrotic elements were engulfed by astrocytes, by unaffected undifferentiated cells or by macrophages. Necrotic debris was rapidly and completely cleared by five days after treatment. Response to the injury induced by MAM was, largely confined to in situ cellular elements. The destruction and repair of the differentiating cells contributed to the pattern of the altered architecture regularly observed following MAM-induced injury to the postnatal cerebellum. Except for their abnormal orientation, Purkinje cells showed no significant alterations. Astrocytic reaction rather than destruction of differentiating cells appeared to be primarily responsible for Purkinje cell misalignment. A few undisturbed parallel fiber-Purkinje cell contacts were identified by electron microscopic study indicating earlier differentiation than described elsewhere. No evidence of presynaptic degeneration was, however, present.

N-acetylglucosamine 6-sulphatase deficiency in a Nubian goat: A model of Sanfilippo syndrome type D (mucopolysaccharidosis IIID)

SummaryA male Nubian goat (SD-1) presented at birth with neurological manifestations consistent with a lysosomal storage disease. Histological studies of tissue obtained at autopsy suggested glycosaminoglycan storage. Total urinary glycosaminoglycan levels, as measured by the uronic acid method, were elevated but overlapped with levels in a younger control goat. However,N-sulphate content was increased 2- to 5-fold, suggestive of heparan sulphate excretion, and this elevation was confirmed by cellulose acetate electrophoresis. Further, urinary levels of freeN-acetylglucosamine 6-sulphate were increased 6-fold over controls, SD-1 cultured skin fibroblasts, labelled with [35S]sulphate, incorporated twice as much radioactivity into macromolecular material as did normal fibroblasts. Forty-eight hours after removal of [35S]sulphate from the medium the SD-1 fibroblasts retained 58% of the label, whereas in control fibroblasts it had declined to 20%, indicative of [35S]proteoglycan storage in SD-1. The assay of fibroblast extracts revealed a profound deficiency ofN-acetylglucosamine 6-sulphatase whereas eight other activities includingβ-mannosidase, arylsulphatase B, iduronate 2-sulphatase,N-acetylgalactosamine 6-sulphatase, and heparin sulphamidase were normal. Mixing of SD-1 sonicates with normal sonicates showed no evidence of an inhibitor, and mixing of SD-1 sonicates with Sanfilippo D cell sonicates yielded no activity. These data ruled out multiple sulphatase deficiency and suggested the first example of the human Sanfilippo syndrome, type D (N-acetylglucosamine 6-sulphatase deficiency) in goats.

α-Mannosidosis in the Guinea Pig: A New Animal Model for Lysosomal Storage Disorders

α-Mannosidosis is a lysosomal storage disorder resulting from deficient activity of lysosomal α-mannosidase. It has been described previously in humans, cattle, and cats, and is characterized in all of these species principally by neuronal storage leading to progressive mental deterioration. Two guinea pigs with stunted growth, progressive mental dullness, behavioral abnormalities, and abnormal posture and gait, showed a deficiency of acidic α-mannosidase activity in leukocytes, plasma, fibroblasts, and whole liver extracts. Fractionation of liver demonstrated a deficiency of lysosomal (acidic) α-mannosidase activity. Thin layer chromatography of urine and tissue extracts confirmed the diagnosis by demonstrating a pattern of excreted and stored oligosaccharides almost identical to that of urine from a human α-mannosidosis patient. Widespread neuronal vacuolation was observed throughout the CNS, including the cerebral cortex, hippocampus, thalamus, cerebellum, midbrain, pons, medulla, and the dorsal and ventral horns of the spinal cord. Lysosomal vacuolation also occurred in many other visceral tissues and was particularly severe in pancreas, thyroid, epididymis, and peripheral ganglion. Axonal spheroids were observed in some brain regions, but gliosis and demyelination were not observed. Ultrastructurally, most vacuoles in both the CNS and visceral tissues were lucent or contained fine fibrillar or flocculent material. Rare large neurons in the cerebral cortex contained fine membranous structures. Skeletal abnormalities were very mild. α-Mannosidosis in the guinea pig closely resembles the human disease and will provide a convenient model for investigation of new therapeutic strategies for neuronal storage diseases, such as enzyme replacement and gene replacement therapies.

Caprine Mucopolysaccharidosis-IIID: Clinical, Biochemical, Morphological and Immunohistochemical Characteristics

Several animal models have been developed for the mucopolysaccharidoses (MPSs), a group of lysosomal storage disorders caused by lysosomal hydrolase deficiencies that disrupt the catabolism of glycosaminoglycans (GAG). Among the MPS, the MPS-III (Sanfilippo) syndromes lacked an animal counterpart until recently. In this investigation of caprine MPS-IIID, the clinical, biochemical, morphological, and immunohistochemical studies revealed severe and mild phenotypes like those observed in human MPS III syndromes. Both forms of caprine MPS HID result from a nonsense mutation and consequent deficiency of lysosomal N-acetylglucosamine 6-sulfatase (G6S) activity and are associated with tissue storage and urinary excretion of heparan sulfate (HS). Using special stains, immunohistochemistry, and electron microscopy, secondary lysosomes filled with GAG were identified in most tissues from affected goats. Primary neuronal accumulation of HS and the secondary storage of gangliosides were observed in the central nervous system (CNS) of these animals. In addition, morphological changes in the CNS such as neuritic expansions and other neuronal alterations that may have functional significance were also seen. The spectrum of lesions was greater in the severe form of caprine MPS HID and included mild cartilaginous, bony, and corneal lesions. The more pronounced neurological deficits in the severe form were partly related to a greater extent of CNS dysmyelination. These findings demonstrate that caprine MPS HID is a suitable animal model for the investigation of therapeutic strategies for MPS III syndromes.

Oligosaccharides accumulated in the kidney of a goat with β-mannosidosis: Mass spectrometry of intact permethylated derivatives

Abstract Two oligosaccharides accumulate in the kidney of a goat with β-mannosidosis. These oligosaccharides were isolated and purified from kidney extracts by Bio-Gel P2 gel permeation column chromatography. Their structures were characterized as Manβ1 → 4GlcNAc and Manβ1 → 4G1cNAcβ1 → 4G1cNAc by mass spectrometry of the permethylated intact oligosaccharide alcohols and permethylated native oligosaccharides. Carbohydrate composition analysis, methylation linkage studies, and enzymatic hydrolysis were also performed. Stored in 1 g of kidney were 1.6 μmol of disaccharide and 7.6 μmol of trisaccharide, which was three times that found in the brain of this affected animal ( M. Z. Jones and R. A. Laine, 1981, J. Biol. Chem., 256, 5181–5184 ). In both the brain and kidney of the affected goat, oligosaccharide accumulation was evidently represented by membrane-bound, electron-lucent vacuoles in numerous cell types. While lesions in the brain were associated with profound neurological deficits, functional impairment of the kidney was not apparent. Similar oligosaccharides excreted in urine may be derived from those stored in the kidney. The mass spectrometric methods utilized in this investigation will facilitate comparison of oligosaccharide composition in different tissues and biological samples in β-mannosidosis and other disorders of glycoprotein catabolism.

Distribution of central nervous system lesions in β-mannosidosis

SummaryCentral nervous system (CNS) morphological changes were delineated in goats affected with β-mannosidosis to determine the extent and distribution of lesions associated with this inherited glycoprotein metabolic perturbation. Coronal sections of one cerebral hemisphere, sagittal sections of one cerebellar hemisphere, and transverse sections of the brain stem of 4- and 16-week-old affected and control goats were analyzed. Lysosomal storage vacuoles, probably representing storage of uncleaved oligosaccharides, were present to various extents in different cell types, with variation in the size of vacuoles. Axonal spheroids were present throughout the white matter, but were most numerous in the rostal thalamic peduncle and brachium of the inferior colliculus. Mineralization occurred only in the globus pallidus and cerebellum. Unlike related storage disorders, severe deficiency of myelin occurred throughout the brain, with regional variation in the extent of myelin deficits. White matter of the corpus callosum, anterior commissure, alvens, fornix, fimbria, and medullary pyramids showed the most severe myelin paucity. Reduction in the number of oligodendroglia and vacuolation of remaining oligodendroglia occurred throughout the white matter. In general, later myelinating tracts showed the most severe myelin deficiency, suggesting that the time of myelination may be a major factor in determining the severity of myelin paucity in β-mannosidosis.

Accumulation of Intracellular Amyloid-β Peptide (Aβ 1–40) in Mucopolysaccharidosis Brains

To evaluate whether in vivo accumulations of heparan sulfate caused by inborn errors in the metabolism of glycosaminoglycans lead to the formation of neurofibrillary tangles and/or senile plaques, as seen in Alzheimer disease (AD), we studied postmortem brains from 9 patients, ages 1 to 42 years, with mucopolysaccharidosis (MPS). The brains of patients with Hurlers syndrome (MPS I: n = 5) and Sanfilippos syndrome (MPS III; n = 4) as well as from caprine MPS IIID and murine MPS VII models were evaluated by thioflavine-S staining and by immunohistochemistry using antibodies directed against heparan sulfate proteoglycans, hyperphosphorylated tau, amyloid-beta peptide precursor proteins (APP), and amyloid-beta peptides (A beta [1-40], and A beta [1-42]). A two-site sandwich enzyme-linked immunosorbent assay (ELISA) was also utilized to compare levels of total soluble and insoluble A beta (1-40) and A beta (1-42) obtained from temporal cortex of MPS patients. Although no neurofibrillary tangles, senile plaques, or tau-positive lesions were detected in any of the MPS brains studied here, antibodies directed against A beta (1-40) intensely and diffusely stained the cytoplasm of cells throughout the brains of the MPS patients and the caprine MPS model. The ELISA assay also demonstrated a significant 3-fold increase in the level of soluble A beta (1-40) in the MPS brains compared with normal control brains. Thus, at least some of the metabolic defects that lead to accumulations of glycosaminoglycans in MPS also are associated with an increase in immunoreactive A beta (1-40) within the cytoplasmic compartment where they could contribute to the dysfunction and death of affected cells in these disorders, but not induce the formation of plaques and tangles. Models of MPS may enable mechanistic studies of the role A beta and glycosaminoglycans play in the amyloidosis that is a neuropathological feature of AD.

AMYLOPECTINOSIS IN FETAL AND NEONATAL QUARTER HORSES

Three Quarter Horses, a stillborn filly (horse No. 1), a female fetus aborted at approximately 6 months of gestation (horse No. 2), and a 1-month-old colt that had been weak at birth (horse No. 3), had myopathy characterized histologically by large spherical or ovoid inclusions in skeletal and cardiac myofibers. Smaller inclusions were also found in brain and spinal cord and in some cells of all other tissues examined. These inclusions were basophilic, red-purple after staining with periodic acid-Schiff (both before and after digestion with diastase), and moderately dark blue after staining with toluidine blue. The inclusions did not react when stained with Congo red. Staining with iodine ranged from pale blue to black. Their ultrastructural appearance varied from amorphous to somewhat filamentous. On the basis of staining characteristics and diastase resistance, we concluded that these inclusions contained amylopectin. A distinctly different kind of inclusion material was also present in skeletal muscle and tongue of horse Nos. 1 and 3. These inclusions were crystalline with a sharply defined ultrastructural periodicity. The crystals were eosinophilic and very dark blue when stained with toluidine blue but did not stain with iodine. Crystals sometimes occurred freely within the myofibers but more often were encased by deposits of amylopectin. This combination of histologic and ultrastructural features characterizes a previously unreported storage disease in fetal and neonatal Quarter Horses, with findings similar to those of glycogen storage disease type IV. We speculate that a severe inherited loss of glycogen brancher enzyme activity may be responsible for these findings. The relation of amylopectinosis to the death of the foals is unknown.