Peter F. Jezyk

β-Glucuronidase Deficiency in a Dog: a Model of Human Mucopolysaccharidosis VII

Summary: This report describes a third mucopolysaccharidosis in animals: canine mucopolysaccharidosis VII. The affected dog was the offspring of a father-daughter mating. Weakness in the rear legs was evident at 8 weeks of age and became progressively worse. He had a large head, a shortened maxilla, and corneal granularities. Most joints were extremely lax, easily subluxated, with joint capsules that were swollen and fluctuant.The dog was alert and had apparently normal pain perception. At 13 months of age, there was radiographic evidence of extensive skeletal disease including bilateral femoral head luxation, abnormalities in the shape and density of the carpal and tarsal bones, radiolucent lesions of the epiphyseal regions of most long bones, and cervical vertebral dysplasia and platyspondylia. The electrophoretic pattern of precipitated glycosaminoglycans indicated a predominance of chondroitin sulfate.The animal died suddenly from gastric dilatation. There was generalized hepatomegaly, thickening of the atrioventricular heart valves, and generalized polyarthropathy. Vacuolated cytoplasm was observed in hepatocytes, keratocytes, fibroblasts, chondrocytes and cells of the synovial membrane, retinal pigment epithelium, and cardiac valves. Neurons had cytoplasmic vacuoles. Electron microscopy demonstrated membrane-bound cytoplasmic inclusions in polymorphonuclear leukocytes, hepatocytes, synovium, heart valves and spleen.The activities of 12 lysosomal hydrolases were determined in liver from the affected and control dogs: β-glucuronidase (EC 3.2.1.31), β-hexosaminidases A and B (EC 3.2.1.30), α-hexosaminidase (EC 3.2.1.-), α-L-iduronidase (EC 3.2.1.76), α-galactosidase A (EC 3.2.1.22), β-galactosidase (EC 3.2.1.23), arylsulfatases A and B (EC 3.1.6.1), acid α-mannosidase (EC 3.2.1.24), acid β-mannosidase (EC 3.2.1.25), and N-acetyl-D-galactosamine-6-sulfate sulfatase (EC 3.1.6.-). The activity of β-glucuronidase was reduced to less than 2% of the normal mean value of normal controls.

Inherited Selective Intestinal Cobalamin Malabsorption and Cobalamin Deficiency in Dogs

ABSTRACT: Inherited selective intestinal malabsorption of cobalamin (Cbl) was observed in a family of giant schnauzer dogs. Family studies and breeding experiments demonstrated simple autosomal recessive inheritance of this disease. Affected puppies exhibited chronic inappetence and failure to thrive beginning between 6 and 12 wk of age. Neutropenia with hypersegmentation, anemia with anisocytosis and poikilocytosis, and megaloblastic changes of the bone marrow were present. Serum Cbl concentrations were low, and methylmalonic atiduria and homocysteinemia were present. Parenteral, but not oral, cyanocobalamin administration rapidly eliminated all signs of Cbl deficiency except for low serum Cbl concentrations. Cbl malabsorption in affected dogs was documented by oral administration of [57Co]cyanocobalamin with or without simultaneous oral administration of intrinsic factor or normal dog gastric juice. Quantitation and function studies of intrinsic factor and transcobalamin-II from affected dogs revealed no abnormality. Other gastrointestinal functions and ileal morphology were normal, indicating a selective defect of Cbl absorption at the level of the ileal enterocyte. Immunoelectron microscopy of ileal biopsies showed that the receptor for intrinsic factor-Cbl complex was absent from the apical brush border microvillus pits of affected dogs. This canine disorder resembles inherited selective intestinal Cbl malabsorption (Imerslund-Grasbeck syndrome) in humans, and is a spontaneously occurring animal model of early onset Cbl deficiency.

Alpha-L-iduronidase deficiency in a cat: a model of mucopolysaccharidosis I.

Summary: A 1-yr-old male domestic shorthair cat was referred to the University of Pennsylvania Veterinary Hospital with a history of progressive lameness. The cat had a short, broad face, frontal bossing, a depressed nasal bridge, small ears, bilateral corneal clouding, and thickened skin over the dorsal aspect of his neck. Radiographically, the cervical vertebrae were wide, assymetrical, and appeared nearly fused; there was bilateral coxofemoral sub-luxation and pectus excavatum. Electrophoresis of glycosamino-glycans (GAG) from the urine revealed an excess of both dermatan sulfate and heparan sulfate. The incorporation of 35SO4 into the GAG of fibroblasts revealed an exaggerated accumulation of [35S] -glycosaminoglycans. By light microscopy, neurons swollen with vacuolated cytoplasm were observed. By electron microscopy, the spinal cord neurons contained membrane-bound “zebra bodies”. Membrane-bound inclusions containing granular material or an occasional myelin-like figure were present in hepatocytes. The activities of seven lysosomal hydrolases (α-L-iduronidase EC. 3.2.1.76, β-D-glucuronidase EC. 3.2.1.31, arylsulfatase A EC. 3.1.6.1, arylsulfatase B EC. 3.1.6.1, α-D-glucosaminidase EC. 3.2.1.50, β-D-glucosaminidase EC. 3.2.1.30, and β-D-galactosidase EC. 3.2.1.33) were investigated in cells from the affected cat. The activity of α-L-iduronidase was deficient in both cultured fibroblasts and peripheral leucocytes, while the activity of the other enzymes was similar to that in normal cats. It is apparent that the pattern of GAG excretion, evidence of lysosomal storage in various tissues, evidence of defective GAG degradation in cultured fibroblasts, and the specific deficiency in activity of α-L-iduronidase in the affected cat parallel closely the findings in mucopolysaccharidosis (MPS) I of man.Speculation: This feline model of MPS I (Hurler, Scheie, or Hurler/Scheie Syndrome) should allow advances in the understanding of the pathogenesis and approaches to therapy for this and related genetic storage diseases.

Mucopolysaccharide Storage Disease in Three Families of Cats with Arylsulfatase B Deficiency: Leukocyte Studies and Carrier Identification

Summary: This report gives a more complete description of pathologic and enzymologic findings in the feline Maroteaux-Lamy Syndrome based on additional studies in the cat originally described, three other affected Siamese cats from two additional families and an affected kitten produced by an experimental mating between obligate heterozygotes from two independently ascertained families.All affected animals had facial dysmorphia with a small head and broad, shortened maxilla. None had hepatosplenomegaly. All had a diffuse ground glass appearance of all layers of the cornea.All long bones had multiple severe exostoses with epiphyseal dysplasia and irregular articular surfaces.There was no indication in these cats of any deficit comparable to what is defined in man as mental retardation.The electrophoretic patterns obtained showed that the primary glycosaminoglycan (GAG) excreted in the urine by the affected cats was dermatan sulfate.In two human mucopolysaccharidoses (MPS) VI patients and all five affected cats, 90–100% of the circulating polymorphonu-clear (PMN) leukocytes contained, by light microscopy, excessive coarse granulations in the cytoplasm. In the human MPS VI patients, most PMN leukocytes contained, by electron microscopy, small (0.2–0.5u) round membrane bound inclusions, a majority of which contained an amorphous to granular electron dense material. The predominant inclusion type in the cat varied among families: lamellar, granular, and crystalloid, but all three inclusion types were present in some cells of all affected individuals.The data indicate that the detection of normals, heterozygotes, and homozygotes for the mutant gene was possible using an assay for arylsulfatase B (ASB) in peripheral blood leukocytes. The existence of an obligate heterozygote which has very low ASB activity with the nitrocatechol sulfate assay indicates that clinical criteria must be combined with assays of enzyme activity before an individual can be defined as affected.Pedigree information in the three independently ascertained families of cats is consistent with autosomal recessive inheritance. An experimental mating between obligate heterozygotes in families 2 and 3 produced a kitten with characteristic signs and enzymatic deficiency of the syndrome, indicating that the same locus, and in all probability the same mutant allele, is involved in these two families.Speculation: This feline model of mucopolysaccharidosis VI (Maroteaux-Lamy Syndrome) can be produced by experimental mating and should allow advances in the understanding of the pathogenesis and approaches to therapy for this and related genetic storage diseases.

Selective IgA deficiency in the dog

This study documents the occurrence of selective IgA deficiency in the dog. This is a unique spontaneous animal model with clinical and immunologic findings similar to that of selective IgA deficiency in humans, the most common human primary immunodeficiency. The disease in the dog is characterized by chronic, recurrent respiratory infections and dermatitis, low concentrations of serum IgA, normal concentrations of serum IgG and IgM, normal T-cell function as measured by lymphocyte transformation tests, the presence of autoantibodies, and a defect in the maturation or terminal differentiation of IgA B cells into IgA-secreting plasma cells.

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.

X-linked severe combined immunodeficiency in the dog.

This study documents the occurrence of a form of X-linked severe combined immunodeficiency (SCID) in the dog with clinical, immunologic, and pathologic features similar to those of X-linked SCID with B cells in man. The disease in the dog is characterized by growth retardation and increased susceptibility to bacterial and viral infections in young pups. Affected pups have all died or were euthanatized by 5 months with signs of canine distemper, infectious hepatitis, or bacterial pneumonia. Laboratory findings include normal numbers of circulating B lymphocytes and normal concentrations of serum IgM, but low to absent concentrations of serum IgG and IgA, indicating a defect in the terminal differentiation of IgG and IgA B cells into immunoglobulin-secreting plasma cells. This is supported by the failure of peripheral lymphocytes to produce IgG or IgA plaque-forming cells in response to polyclonal activation. There are low-to-normal numbers of circulating T cells, but a severely depressed blastogenic response to T cell mitogens. Postmortem findings include thymic dysplasia and hypoplasia of lymphoid tissue. Family studies and breeding experiments are consistent with an X-linked recessive mode of inheritance.

Models of Human Genetic Disease in Domestic Animals

It is well recognized that naturally occurring diseases of animals can provide insights into the causal mechanisms, pathogenesis, and therapy of human disease.37,55,75,117,170,224 Animal models are particularly useful in the study of genetic disorders, in which the chain of events between the underlying cause and the pathologic phenotype is difficult or impossible to study in man (e.g., pathogenesis of congenital malformations), or in which evaluation of therapy requires a whole mammalian organism (e.g., enzyme replacement therapy in metabolic disease). Since accurate models of genetic disorders cannot be readily produced by experimental manipulation of normal laboratory animals, genetically determined counterparts of human disease in animals offer the most plausible alternative.

Organic aciduria and butyryl CoA dehydrogenase deficiency in BALB/cByJ mice

A metabolic screening program of inbred strains of mice has detected a marked organic aciduria in the BALB/cByJ strain. Gas chromatographic and mass spectrometric analysis identified large quantities ofn-butyrylglycine plus lesser quantities of ethylmalonic acid. Crosses with the nonexcreting C57BL/6J strain indicate that this condition is inherited as an autosomal recessive trait. Independently from this screening a variant with no detectable enzyme activity of butyryl CoA dehydrogenase (BCD) in liver and kidney of the BALB/cByJ strain but not other BALB/c sublines was discovered. Data from a three-point cross indicated that the null variant maps to the structural locus for the enzyme,Bcd-1, on chromosome 5. The findings indicate that a mutation at or nearBcd-1 in the BALB/cByJ strain resulted in a biochemical abnormality manifest as the BCD deficiency. It is concluded that accumulation of butyryl CoA due to a block in the oxidation of short-chain fatty acids results in an overproduction of organic metabolites leading to the observed organic aciduria. The fact that other BALB/c substrains do not exhibit this abnormality further suggests that this disorder reflects subline divergence within the BALB/c family.

Familial Glomerulonephropathy in the Bullmastiff

Glomerular disease was diagnosed by histopathologic examination in 11 related Bullmastiff dogs, and clinical and laboratory data were collected retrospectively. Four female and seven male dogs between the ages of 2.5 and 11 years were affected. Clinical signs, including lethargy and anorexia, were nonspecific and occurred shortly before death or euthanasia. In five affected dogs serial blood samples were obtained, and dramatically elevated blood urea nitrogen and creatinine levels were demonstrated up to 2.75 years before death. Protein-creatinine ratios were elevated in six of six dogs and were above normal 3.5 years before death in one dog. The kidneys appeared grossly normal to slightly smaller than normal at necropsy. Histologic abnormalities of the kidneys were consistent with chronic glomerulonephropathy with sclerosis. Examination of the pedigrees of related affected dogs yielded evidence supporting an autosomal recessive mode of inheritance.