Hereditary myelopathy of Afghan hounds, a myelinolytic disease

TSEN54 missense variant in Standard Schnauzers with leukodystrophy

We report a hereditary leukodystrophy in Standard Schnauzer puppies. Clinical signs occurred shortly after birth or started at an age of under 4 weeks and included apathy, dysphoric vocalization, hypermetric ataxia, intension tremor, head tilt, circling, proprioceptive deficits, seizures and ventral strabismus consistent with a diffuse intracranial lesion. Magnetic resonance imaging revealed a diffuse white matter disease without mass effect. Macroscopically, the cerebral white matter showed a gelatinous texture in the centrum semiovale. A mild hydrocephalus internus was noted. Histopathologically, a severe multifocal reduction of myelin formation and moderate diffuse edema without inflammation was detected leading to the diagnosis of leukodystrophy. Combined linkage analysis and homozygosity mapping in two related families delineated critical intervals of approximately 29 Mb. The comparison of whole genome sequence data of one affected Standard Schnauzer to 221 control genomes revealed a single private homozygous protein changing variant in the critical intervals, TSEN54:c.371G>A or p.(Gly124Asp). TSEN54 encodes the tRNA splicing endonuclease subunit 54. In humans, several variants in TSEN54 were reported to cause different types of pontocerebellar hypoplasia. The genotypes at the c.371G>A variant were perfectly associated with the leukodystrophy phenotype in 12 affected Standard Schnauzers and almost 1000 control dogs from different breeds. These results suggest that TSEN54:c.371G>A causes the leukodystrophy. The identification of a candidate causative variant enables genetic testing so that the unintentional breeding of affected Standard Schnauzers can be avoided in the future. Our findings extend the known genotype-phenotype correlation for TSEN54 variants.

Various hereditary diseases of the cerebral white matter occur in humans and dogs. We describe a new leukodystrophy in Standard Schnauzers. Genetic mapping and whole genome sequence analysis identified a likely candidate causative variant in the TSEN54 gene encoding tRNA splicing endonuclease 54. These results provide new information about the role of TSEN54 in cell metabolism and the development of the central nervous system in the late gestational and early post-natal period. The affected dogs potentially represent a translational large animal model for similar leukoencephalopathies in human medicine. The clinical phenotype in Schnauzers included multifocal central nervous system signs. A holistic pathogenically driven understanding of disease initiation and perpetuation requires a solid analysis of the underlying genetics and characterization of the disease phenotype at the clinical and cellular as well as sub-cellular level. In contrast to the canine phenotype with a predominant manifestation in the cerebrum white matter, other TSEN54 variants in humans have been reported to result in a different pathological phenotype characterized by pontocerebellar hypoplasia. The differences between humans and dogs underscore the need for comparative analysis at the clinical, pathological and molecular level to understand species-specific protein mediated pathways, interactions and outcomes.

A leukomyeloencephalopathy of unknown origin in an Azawakh dog

A diffuse bilaterally symmetrical leukomyeloencephalopathy was observed in a 6-year-old male Azawakh dog showing a slowly progressive ataxia of six months duration associated with sensory disorders. Severe bilaterally symmetrical demyelination and vacuolisation were confined to the dorsal columns along the entire spinal cord with a minor axonal degeneration. The main changes of myelin sheaths consisted in splitting and intramyelin vacuolization. Naked axons were scattered in a network of astrocytic processes and collagen fibres. Few reactive macrophages exhibiting a foamy pattern were observed adjacent to the small vessels. In the brain, cuneatus nuclei showed a number of atrophic neurons. A spongy change was observed in the raphe nuclei, spinal tract and nuclei of trigeminal nerve, and caudal cerebellar peduncles. Lesions there were neither in the spinal and trigeminal nerves, nor in the spinal ganglia. Although in the absence of a pedigree analysis support an inherited cause cannot be completely excluded.

Leukoencephalopathy associated with parvovirus infection in Cretan hound puppies

Leukoencephalopathies in dogs encompass presumably inherited conditions such as leukodystrophies, hypomyelination or spongiform degeneration, but other causes, such as virus infections and toxic or nutritional factors, might also play a contributory role. In this report, we provide evidence of parvovirus infection and replication in the brains of five 6-week-old Cretan hound puppies suffering from a puppy shaker syndrome and leukoencephalopathy. Although these puppies belonged to two different litters, they were closely related, tracing back two generations to the same sire. Histologically, a mild to moderate lymphohistiocytic meningitis, with focal lymphohistiocytic leukoencephalitis in two animals, and a mild to moderate vacuolation with myelin loss, mainly in the white matter of the cerebellum was detected. Vacuolation was also found in the corpus callosum, fimbria hippocampi, mesencephalon, capsula interna, basal ganglia, and hypothalamus. By immunohistology and in situ hybridization, either parvoviral antigen, DNA, mRNA, or replicative intermediate DNA were detected in the cerebellum, hippocampus, periventricular areas, corpus callosum, cerebral cortex, medulla oblongata, and spinal cord. Parvovirus antigen, DNA, and mRNA were present in cells of the outer granular layer of the cerebellum and in periventricular cells, most likely representing spongioblasts, glial cells, neurons, endothelial cells, occasional macrophages, and ependymal cells. Sequencing revealed canine parvovirus type 2 stretches. Thus, an association of parvovirus infection with the leukoencephalopathy seems likely, possibly facilitated by a genetic predisposition due to the mode of inbreeding in this particular dog breed.

A novel leucodystrophy in a dog

A diffuse, bilaterally symmetrical leucoencephalopathy was observed in a 2-month-old female crossbred puppy with a clinical history of progressive tetraparesis with front limb hypermetria, head tremor and seizures. Severe myelinolytic lesions with significant macrophage infiltration were confined to the white matter, mainly of the cerebellum and spinal cord. Moderate loss of myelin with severe gliosis predominated in the cerebrum. Axonal degeneration and axonal loss accompanied myelin degeneration. This disease was classified as a leucodystrophy. The clinical signs and certain features of the lesions (morphology and distribution), differed from those in previously described degenerative myelinolytic diseases in animals. The possible occurrence of the disorder in a littermate suggested a genetic basis.

A presumed inherited spongiform leucoencephalomyelopathy of Romney lambs in New Zealand

This paper records a unique ovine encephalomyelopathy seen on several farms in the Otago Region of New Zealand. It occurred in 2-3 month-old Romney lambs as a rapidly progressive posterior paresis leading to flaccid paralysis. Pathologically, it was characterised by severe spongy vacuolation of white matter in both brain and spinal cord. It is suspected that the condition is inherited.

Hereditary necrotising myelopathy in Kooiker dogs

A retrospective clinicopathological study of a neurological disorder in 22 Kooiker dogs (Dutch decoy dog) was made. The disease was found to occur equally in both sexes and clinical signs began at three to 12 months old. Physical examination revealed a progressive paresis of the hindlimbs. Post mortem examination showed symmetrical areas of malacia in the ventral, lateral and dorsal white matter of the spinal cord. In one dog dorsal white matter was spared. Cervical segments C4 to C8 were involved in all subjects. Rostral and caudal to these areas, Wallerian degeneration was prominent. The disease has much in common with similar myelopathies in the Afghan hound and the rottweiler. Indications of heritability were the similarity in clinical and pathological findings, the age of onset of the disease, and the significantly higher inbreeding coefficient in the patients than in the breed population (P = 0.001). All patients were descended from one pair. Segregation analysis suggested inheritance involving a simple autosomal recessive trait.

Leucoencephalomyelopathy in Australian Rottweiler dogs

Clinical and pathological studies of a neurological disorder of 3 adult Rottweiler dogs are described. Dogs developed proprioceptive losses involving the limbs, leading to progressively worsening ataxia and hypermetria. Blood and CSF fluid analyses were normal and radiographs and myelograms showed no compressive lesions of the spinal cord. At necropsy, severe demyelination of the dorsal and lateral funiculi of the cervical spinal cord was visible grossly. Microscopically there was more extensive, symmetrical involvement of the spinal cord and brain than was apparent grossly, with demyelination of white matter tracts and sparing of axons in affected areas. These changes were considered diagnostic for leucoencephalomyelopathy. This condition has not been previously reported in Australia, and is probably transmitted genetically, presumably as an autosomal recessive trait.

Progressive ataxia due to central demyelination in Rottweiler dogs

A clinicopathological study of a neurologic disease in Rottweiler dogs was conducted. Clinical data were available on 16 dogs, 11 of which were examined pathologically. All dogs had a history of progressive gait abnormalities, which had commenced insidiously at an age varying from 1.5 to 3.5 years. In most dogs the fore limbs were affected prior to the hind limbs. At neurologic examination ataxia of all 4 limbs was seen, in some instances accompanied by an apparent paresis. Proprioceptive positioning was delayed whereas spinal reflexes were often hyperactive. Plain and contrast radiographs of the spine did not reveal any compressive lesions in 5 dogs examined. Cerebrospinal fluid analysis in 4 dogs was normal. Electrodiagnostic testing in 3 dogs revealed no abnormalities. At pathologic examination demyelinating lesions were found in the central nervous system. These were largely confined to the cervical spinal cord and brain stem and had a rather characteristic more or less symmetric distribution. Pedigree data suggested that the disease is transmitted genetically.

A progressive spinal myelinopathy in beef cattle

Ataxia of the hind limbs in nine calves was associated with degenerative lesions in spinal white matter and neuronal chromatolysis in red nucleus, spinal grey matter and various nuclei of the medulla oblongata and cerebellum. The clinical signs and lesions were similar to those observed in enzootic ataxia of red deer and occurred predominantly in calves of the Murray Grey breed. The pathogenesis appears to involve a primary defect in central nervous system myelin with progressive myelin loss primarily in the spinal cord.

A leukoencephalomyelopathy of rottweiler dogs

Two adult rottweiler dogs were evaluated for slowly progressive ataxia and paresis of all four limbs of over seven months duration. On neurologic examination, signs referable to a lesion in the cervical spinal cord affecting motor and sensory white matter tracts were found. Both dogs were necropsied and were found to have demyelinating lesions in the spinal cord, brain stem, and deep cerebellar white matter. Primary morphologic alterations were intact naked axons and thinly myelinated axons accompanied by reactive astrogliosis. The spinal cord lesions tended to have bilateral symmetry and were found in the lateral funiculi and occasionally in the dorsal funiculi. The cause and pathogenesis of the lesion were not determined.