Temporospatial Development of Neuropathologic Findings in a Canine Model of Mucopolysaccharidosis IIIB.

Mucopolysaccharidosis (MPS) IIIB is a neuropathic lysosomal storage disease characterized by the deficient activity of a lysosomal enzyme obligate for the degradation of the glycosaminoglycan (GAG) heparan sulfate (HS). The pathogenesis of neurodegeneration in MPS IIIB is incompletely understood. Large animal models are attractive for pathogenesis and therapeutic studies due to their larger size, outbred genetics, longer lifespan, and naturally occurring MPS IIIB disease. However, the temporospatial development of neuropathologic changes has not been reported for canine MPS IIIB. Here we describe lesions in 8 brain regions, cervical spinal cord, and dorsal root ganglion (DRG) in a canine model of MPS IIIB that includes dogs aged from 2 to 26 months of age. Pathological changes in the brain included early microscopic vacuolation of glial cells initially observed at 2 months, and vacuolation of neurons initially observed at 10 months. Inclusions within affected cells variably stained positively with PAS and LFB stains. Quantitative immunohistochemistry demonstrated increased glial expression of GFAP and Iba1 in dogs with MPS IIIB compared to age-matched controls at all time points, suggesting neuroinflammation occurs early in disease. Loss of Purkinje cells was initially observed at 10 months and was pronounced in 18- and 26-month-old dogs with MPS IIIB. Our results support the dog as a replicative model of MPS IIIB neurologic lesions and detail the pathologic and neuroinflammatory changes in the spinal cord and DRG of MPS IIIB-affected dogs.

Mucopolysaccharidosis IIIB (Sanfilippo syndrome B) in a commercial emu (Dromaius novaehollandiae) flock.

Clinicopathological diagnosis of mucopolysaccharidosis type IIIB (MPS IIIB; Sanfilippo syndrome B), an inherited autosomal recessive lysosomal storage disease, as a cause of losses in a commercial emu flock and screening breeders using a mutation-specific DNA test are described. Between 2012 and 2015, ∼5-10 juvenile emus from a few weeks to several months of age developed progressive neurological signs and died while others in the flock remained healthy. Necropsy of two affected siblings revealed multiple sites of haemorrhage, cytoplasmic periodic acid-Schiff and Luxol fast blue-positive inclusions in neurons, and aggregates of foamy macrophages in visceral organs. Affected emus were homozygous for the two-base deletion in the α-N-acetylglucosaminidase gene that causes MPS IIIB in emus. Mutation-specific DNA tests for MPS IIIB in emus were developed. Screening blood samples from 78 breeding emus revealed 14 (18%; 9 males, 4 females, and 1 unknown gender) carriers; an overall 0.09 mutant α-N-acetylglucosaminidase allele frequency. A "test and cull male carriers" programme, in which carrier males are culled but carrier females are retained, was proposed to avoid breeding affected emus together, ultimately eliminating the disease from future broods, and preserving the gene pool with as much breeding stock as possible. Molecular genetic diagnostic tests are simple, precise, and permit screening of all breeders for the mutant allele in any flock and can be used to eliminate MPS IIIB-related emu losses through informed breeding.

Pathological and biochemical studies of mucopolysaccharidosis type IIIB (Sanfilippo syndrome type B) in juvenile emus (Dromaius novaehollandiae).

Mucopolysaccharidosis (MPS) type IIIB was diagnosed in 14 juvenile emus (Dromaius novaehollandiae), ages 3 weeks to 6 months, based on pathological and biochemical analyses. The animals had a history of neurological signs or sudden death; one of the birds with neurological signs and 3 others experienced acute hemoabdomen. Histopathologically, neuronal swelling and vacuolation in the cerebrum, cerebellum, brainstem, and spinal cord (80%-92%); retina (100%); autonomic ganglia of the intestine (71%); gizzard (50%); adrenal gland (27%); and ear (50%) were noted in affected but not healthy emus. Cytoplasmic vacuoles were also observed in the pancreas, liver, intestine, adrenal glands, and kidneys. The intracytoplasmic inclusions were periodic acid-Schiff and Luxol Fast Blue positive, consistent with a storage disease. Foamy macrophages infiltrated the liver, intestine, tunica media of the aorta, and spleen. By transmission electron microscopy, typical lamellated cytoplasmic bodies were detected in neurons of the brain and retina, while electron-dense bodies consistent with glycosaminoglycan inclusions were observed in hepatocytes and/or hepatic macrophages. The livers of the 2 affected emus studied contained large amounts of heparan sulfate, which is suggestive of MPS type III. Compared with normal controls, hepatic and serum α-N-acetylglucosaminidase activity was very low (<8% of control), while other enzyme activities were normal to increased in the 2 affected emus studied. Moreover, affected emus were homozygous for a 2-bp deletion in the NAGLU gene. This study characterizes the pathology of MPS type IIIB in emus, which is one of the rare inborn errors in birds, showing the homology of this condition to Sanfilippo syndrome in humans.

Pathology of mucopolysaccharidosis IIIA in Huntaway dogs.

Dogs with mucopolysaccharidosis (MPS) IIIA were bred within an experimental colony. As part of characterizing them as a model for testing therapeutic strategies for the analogous disease of children, a pathologic study was undertaken. By histology, there were variably stained storage cytosomes within neurons, including many that stained for gangliosides. On ultrastructure examination, these cytosomes contained either moderately dense granular material, tentatively interpreted as precipitated glycosaminoglycan; a variety of multilaminar bodies, interpreted as being associated with secondary accumulation of gangliosides; or a mixture of both types. In the liver, storage vesicles also contained excess glycogen as a secondary storage product. In various tissues, there were large foamy macrophages. In the brain, many of these were in juxtaposition with neurons, and, on ultrastructure examination, they contained storage cytosomes similar to those in neurons. However, the neuron in association with such a macrophage frequently showed little such material.

Bovine mucopolysaccharidosis type IIIB.

Mucopolysaccharidosis IIIB, an autosomal recessive lysosomal storage disorder of heparan sulfate caused by mutations in the alpha-N-acetylglucosaminidase (NAGLU) gene, was recently discovered in cattle. Clinical signs include progressive ataxia, stumbling gait, swaying and difficulty in balance and walking. These clinical signs are usually first observed at approximately 2 years of age and then develop progressively over the lifespan of the animals. Affected bulls were found to be homozygous for the missense mutation E452K (c.1354G > A). The availability of mutational analysis permits screening for the NAGLU mutation to eradicate this mutation from the cattle breeding population.

Identification of a mutation causing mucopolysaccharidosis type IIIA in New Zealand Huntaway dogs.

Mucopolysaccharidosis type IIIA (MPS IIIA) is an autosomal recessive disease that occurs due to a deficiency of heparan sulfate sulfamidase (SGSH). The deficiency of SGSH results in the lysosomal accumulation and urinary excretion of the glycosaminoglycan heparan sulfate. The clinical severity of MPS IIIA is predominantly characterized by severe central nervous system degeneration. Naturally occurring MPS IIIA has recently been described in New Zealand Huntaway dogs, with similar disease progression and biochemical characteristics observed in severely affected MPS IIIA patients. Here, we identify the disease-causing mutation in the MPS IIIA Huntaway dog as 708-709insC. The frequency of the 708-709insC mutation in a sample group of 203 New Zealand Huntaway dogs was determined to be 3.8%. The identification of the 708-709insC mutation will permit the identification of heterozygous carriers as an initial step toward establishing a breeding colony of MPS IIIA dogs for the study of various therapeutic strategies targeted to the central nervous system.

Histological diagnosis of mucopolysaccharidosis IIIA in a wire-haired dachshund.

A four-year-old wire-haired dachshund developed progressive neurological signs of ataxia, intention tremor and finally dysuria. Two years later, histopathology showed that neurons throughout the brain and spinal cord were distended with lipopigment which was also present in macrophages. Ultrastructurally, the pigment in the neurons occurred predominantly as electron-dense membranous whorls and stacks. There were a few vacuolated macrophages in the meninges. Hepatocytes were highly vacuolated and electron microscopy suggested that they were empty membrane-bound vesicles. The disease was diagnosed as mucopolysaccharidosis IIIA because of its similarity to other biochemically confirmed cases in the same breed and in a New Zealand huntaway dog. Additional lesions included calcium oxalate uroliths, severe secondary calcification of tissues including the brain and storage deposits in some neurons, and lesions which may have been associated with high levels of the substrate, heparan sulphate.

Sulfamidase deficiency in a family of Dachshunds: a canine model of mucopolysaccharidosis IIIA (Sanfilippo A).

Mucopolysaccharidosis IIIA (MPS IIIA or Sanfilippo A, McKusick 25290) was diagnosed in two adult wire-haired Dachshund littermates. Clinical and pathologic features paralleled the human disorder; both dogs exhibited progressive neurologic disease without apparent somatic involvement. Pelvic limb ataxia was observed when the dogs were 3 y old and progressed gradually within 1-2 y to severe generalized spinocerebellar ataxia. Mentation remained normal throughout the course of the disease. A mucopolysaccharide storage disorder was indicated in both dogs by positive toluidine blue spot tests of urine. The diagnosis of MPS IIIA was confirmed by documentation of urinary excretion and tissue accumulation of heparan sulfate and decreased sulfamidase activity in fibroblasts and hepatic tissue. Mild cerebral cortical atrophy and dilation of the lateral ventricles were grossly evident in both dogs. Light microscopically, fibroblasts, hepatocytes, and renal tubular epithelial cells were vacuolated. Within the nervous system, cerebellar Purkinje cells, neurons of brainstem nuclei, ventral and dorsal horns, and dorsal ganglia were distended with brightly autofluorescent, periodic acid-Schiff-positive, sudanophilic material. Ultrastructurally, visceral storage presented as membrane-bound vacuoles with finely granular, variably electron-lucent contents. Neuronal storage appeared as membranous concentric whorls, lamellated parallel membrane stacks, or electron-dense lipid-like globules. This represents the first reported animal disease homolog of the human Sanfilippo A syndrome.

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 IIID 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 IIID 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 IIID is a suitable animal model for the investigation of therapeutic strategies for MPS III syndromes.