In other species: domestic cat , sheep , Rhesus monkey

Possibly relevant human trait(s) and/or gene(s) (MIM number): 245200 (trait)

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal Recessive

Considered a defect: yes

Key variant known: yes

Year key variant first reported: 1996

Cross-species summary: Also known as globoid cell leukodystrophy (GLD), galactosylceramide lipidosis, galactocerebrosidase deficiency, GALC deficiency, globoid cell leukoencephalopathy, galactosylceramide beta-galactosidase deficiency. A lysosomal storage disease in which there is a buildup (storage) of myelin, due to the lack of the enzyme galactosylceramidase (galactocerebrosidase), whose task is to break down myelin into its constituent molecules. Characterised by weakness progressing to paralysis.

Species-specific name: globoid cell leukodystrophy

Species-specific symbol: GLD

Molecular basis: By cloning and sequencing a very likely comparative candidate gene (based on the homologous human disorder), Victoria et al. (1996) identified the cause of this disorder, in both West Highland White terriers and Cairn terriers, as a base substitution (A to C transversion) at position 473 of the cDNA for galactocerebriosidase (GALC), resulting in an amino acid substitution (tyrosine to serine) at position 158 in the peptide. They have developed a PCR genotyping test which is being used within both breeds, to identify carriers.

In an Irish Setter family, McGraw and Carmichael (2006) identified a 78 bp insertion in the same gene as the causative mutation.

Clinical features: Clinical signs are usually apparent in affected dogs by 4-6 weeks of age (Corado et al., 2020). Affected dogs initially present with tremors and pelvic limb weakness which then progresses to pelvic limb ataxia as well as thoracic limb dysmetria, followed by tetraparesis and then eventually hind limb paralysis (Corado et al., 2020). Other clinical signs may include a wide-based stance, hypermetria, generalised incoordination and muscle atrophy (Bradbury et al., 2018). [IT thanks DVM student Sharna Allison, who provided the basis of this contribution in April 2022]

Pathology: This disease results in extensive characteristic white matter demyelination, globoid cell infiltration and low leukocyte galactosylceramidase activity (Fletcher et al., 2010). Demyelination usually begins in the spinal cord, peripheral nerves and hindbrain before progressing to the cerebellum (Fletcher et al., 2010). Histopathological changes in GLD-affected dogs include reactive astrocytosis and microglial activation (Fletcher et al., 2010). Psychosine, a GALC substrate, is believed to be responsible for cell death in GLD (Corado et al., 2020). [IT thanks DVM student Sharna Allison, who provided the basis of this contribution in April 2022]

Breeds: Australian Kelpie, Basset Hound, Beagle, Bluetick Hound, Cairn Terrier, Dalmatian, Irish Setter, Miniature Poodle, Rottweiler, West Highland White Terrier.

Associated gene: