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Genome-wide mRNA sequencing of a single canine cerebellar cortical degeneration case leads to the identification of a disease associated SPTBN2 mutation.

ABSTRACT: BACKGROUND: Neonatal cerebellar cortical degeneration is a neurodegenerative disease described in several canine breeds including the Beagle. Affected Beagles are unable to ambulate normally from the onset of walking and the main pathological findings include Purkinje cell loss with swollen dendritic processes. Previous reports suggest an autosomal recessive mode of inheritance. The development of massively parallel sequencing techniques has presented the opportunity to investigate individual clinical cases using genome-wide sequencing approaches. We used genome-wide mRNA sequencing (mRNA-seq) of cerebellum tissue from a single Beagle with neonatal cerebellar cortical degeneration as a method of candidate gene sequencing, with the aim of identifying the causal mutation. RESULTS: A four-week old Beagle dog presented with progressive signs of cerebellar ataxia and the owner elected euthanasia. Histopathology revealed findings consistent with cerebellar cortical degeneration. Genome-wide mRNA sequencing (mRNA-seq) of RNA from cerebellum tissue was used as a method of candidate gene sequencing. After analysis of the canine orthologues of human spinocerebellar ataxia associated genes, we identified a homozygous 8 bp deletion in the ?-III spectrin gene, SPTBN2, associated with spinocerebellar type 5 in humans. Genotype analysis of the sire, dam, ten clinically unaffected siblings, and an affected sibling from a previous litter, showed the mutation to fully segregate with the disorder. Previous studies have shown that ?-III spectrin is critical for Purkinje cell development, and the absence of this protein can lead to cell damage through excitotoxicity, consistent with the observed Purkinje cell loss, degeneration of dendritic processes and associated neurological dysfunction in this Beagle. CONCLUSIONS: An 8 bp deletion in the SPTBN2 gene encoding ?-III spectrin is associated with neonatal cerebellar cortical degeneration in Beagle dogs. This study shows that mRNA-seq is a feasible method of screening candidate genes for mutations associated with rare diseases when a suitable tissue resource is available.

SUBMITTER: Forman OP

PROVIDER: S-EPMC3413603 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Genome-wide mRNA sequencing of a single canine cerebellar cortical degeneration case leads to the identification of a disease associated SPTBN2 mutation.

Forman Oliver P OP De Risio Luisa L Stewart Jennifer J Mellersh Cathryn S CS Beltran Elsa E

BMC genetics 20120710

<h4>Background</h4>Neonatal cerebellar cortical degeneration is a neurodegenerative disease described in several canine breeds including the Beagle. Affected Beagles are unable to ambulate normally from the onset of walking and the main pathological findings include Purkinje cell loss with swollen dendritic processes. Previous reports suggest an autosomal recessive mode of inheritance. The development of massively parallel sequencing techniques has presented the opportunity to investigate indivi ...[more]

PMID: 22781464

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Project description:BackgroundCerebellar cortical degeneration (CCD) is an increasingly recognised neurodegenerative disease process affecting many dog breeds. Typical presentation consists of a progressive cerebellar ataxia, with a variable age at onset and rate of progression between different breeds. Cerebellar histopathological findings typically consist of primary Purkinje neuronal degeneration and loss, with variable secondary depletion of the granular and molecular cell layers. Causative genes have been identified associated with CCD in several breeds, allowing screening for selective breeding to reduce the prevalence of these conditions. There have been no previous reports of CCD in Hungarian Vizslas.ResultsTwo full-sibling Hungarian Vizsla puppies from a litter of nine presented with a history of progressive ataxia, starting around three months of age. Clinical signs included marked hypermetric and dysmetric ataxia, truncal sway, intention tremors and absent menace responses, with positional horizontal nystagmus in one dog. Routine diagnostic investigations were unremarkable, and magnetic resonance imaging performed in one dog revealed mild craniodorsal cerebellar sulci widening, supportive of cerebellar atrophy. Owners of both dogs elected for euthanasia shortly after the onset of signs. Histopathological examination revealed primary Purkinje neuron loss consistent with CCD. Whole genome sequencing was used to successfully identify a disease-associated splice donor site variant in the sorting nexin 14 gene (SNX14) as a strong causative candidate. An altered SNX14 splicing pattern for a CCD case was demonstrated by RNA analysis, and no SNX14 protein could be detected in CCD case cerebellum by western blotting. SNX14 is involved in maintaining normal neuronal excitability and synaptic transmission, and a mutation has recently been found to cause autosomal recessive cerebellar ataxia and intellectual disability syndrome in humans. Genetic screening of 133 unaffected Hungarian Vizslas revealed the presence of three heterozygotes, supporting the presence of carriers in the wider population.ConclusionsThis is the first report of CCD in Hungarian Vizsla dogs and identifies a highly associated splice donor site mutation in SNX14, with an autosomal recessive mode of inheritance suspected.

Project description:See King et al. (doi:10.1093/aww348) for a scientific commentary on this article.Detailed mapping of clinical dysfunctions to the cerebellar lobules in disease populations is necessary to establish the functional significance of lobules implicated in cognitive and motor functions in normal subjects. This study constitutes the first quantitative examination of the lobular correlates of a broad range of cognitive and motor phenomena in cerebellar disease. We analysed cross-sectional data from 72 cases with cerebellar disease and 36 controls without cerebellar disease. Cerebellar lobule volumes were derived from a graph-cut based segmentation algorithm. Sparse partial least squares, a variable selection approach, was used to identify lobules associated with motor function, language, executive function, memory, verbal learning, perceptual organization and visuomotor coordination. Motor dysfunctions were chiefly associated with the anterior lobe and posterior lobule HVI. Confrontation naming, noun fluency, recognition, and perceptual organization did not have cerebellar associations. Verb and phonemic fluency, working memory, cognitive flexibility, immediate and delayed recall, verbal learning, and visuomotor coordination were variably associated with HVI, Crus I, Crus II, HVII B and/or HIX. Immediate and delayed recall also showed associations with the anterior lobe. These findings provide preliminary anatomical evidence for a functional topography of the cerebellum first defined in task-based functional magnetic resonance imaging studies of normal subjects and support the hypotheses that (i) cerebellar efferents target frontal lobe neurons involved in forming action representations and new search strategies; (ii) there is greater involvement of the cerebellum when immediate recall tasks involve more complex verbal stimuli (e.g. longer words versus digits); and (iii) it is involved in spontaneous retrieval of long-term memory. More generally, they provide an anatomical background for studies that seek the mechanisms by which cognitive and motor dysfunctions arise from cerebellar degeneration. Beyond replicating these findings, future research should employ experimental tasks to probe the integrity of specific functions in cerebellar disease, and new imaging methods to quantitatively map atrophy across the cerebellum.

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Genome-wide mRNA sequencing of a single canine cerebellar cortical degeneration case leads to the identification of a disease associated SPTBN2 mutation.

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Genome-wide mRNA sequencing of a single canine cerebellar cortical degeneration case leads to the identification of a disease associated SPTBN2 mutation.

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