In other species: emu , domestic cat , taurine cattle , sheep

Categories: Lysosomal storage disease , Nervous system phene

Links to possible relevant human trait(s) and/or gene(s) in OMIM: 230500 (trait) , 230650 (trait) , 230600 (trait) , 253010 (trait) , 611458 (gene)

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal recessive

Disease-related: yes

Key variant known: yes

Year key variant first reported: 2000

Cross-species summary: A lysosomal storage disease in which there is a buildup (storage) of GM1 gangliosides (a type of glycolipid) in various tissues, due to the lack of the enzyme beta-galactosidase, whose task is to break down the GM1 ganglioside into its constituents. Characterised by progressive neuromuscular dysfunction and impaired growth from an early age.

Species-specific description: GM1 gangliosidosis is a lysosomal storage disease caused by beta galactosidase deficiency and characterized by progressive neurological deterioration. It is caused by mutations in GLB1, although the mutations differ by breed. There is a genetic test available.

Mapping: CFA23

Molecular basis: By cloning and sequencing a very likely comparative candidate gene (based on the homologous human disorder), Wang et al. (2000) showed that the causative mutation in Portuguese water dogs is a G to A transition in exon 2 of the GLB1 gene, that causes an amino acid change from arginine to histidine in the resultant peptide. The causative mutation in Shiba dogs is a deletion of a cytosine in exon 15 that causes a premature stop codon in GLB1 (Yamato et al., 2002). The causative mutation in Alaskan huskies is a 19 base pair duplication in exon 15 that variably disrupts mRNA splicing and result in no functional GLB1 (Kreutzer et al., 2005).

Clinical features: Affected dogs generally have proportional dwarfism, which is easily observed in the Alaskan husky, and all develop progressive cerebellar dysfunction and limb weakness. Signs include weight loss, ataxia, wide-based gait, decreased proprioception, intention tremor of the head, ataxia, hypermetria, dysmetria, internal strabismus, and positional nystagmus. Signs begin around 6 to 8 weeks of age, and are clearly noticeable by 7 months of age. Abnormal endochondral ossification of vertebral epiphyses was visible in radiographs of 5.5 month old affected Alaskan huskies. Affected dogs occasionally have an increase in serum ALP. Coarse facial features are seen in affected English springer spaniels (Müller et al., 2001, Alroy et al., 1992). Bone marrow transplantation therapy was attempted but ineffective in affected Portugese water dogs (O’Brien et al., 1990).

Pathology: Affected dogs are deficient in acid beta-galactosidase and are unable to completely degrade complex oligosaccharides. The result is lysosomal accumulation of GM1 gangliosides and other galactose-containing glycoconjugates with a nonreduced terminal beta-galactosidic linkage (Müller et al., 2001). On histologic examination, most neurons in the central nervous system contain densely packed, PAS positive cytoplasmic inclusions, giving the appearance of foamy or granular cytoplasm. Other changes include mild demyelination, axonal degeneration, significant astrogliosis, and significant loss of oligodendrocytes (Müller et al., 2001). Vacuoles are also found in hepatocytes and renal tubular epithelial cells (Shell et al 1989).

Prevalence: The frequency of heterozygotes in normal (unaffected) Shiba Inu dogs in Japan has been reported by Yamato et al. (2008) as 2/68 (2.94%) and by Uddin et al. (2013) as 6/590 (1.02%). In unaffected miniature Shibu Inu (called Mame Shiba), Pervin et al. (2022) reported a heterozygote frequency of 9/1832 (= 0.49%).

Control: Relatives of affected dogs should be tested and breeding of affected or carrier dogs should be avoided.

Genetic testing: There are tests available to detect the known causative mutations.

Breeds: Alaskan Husky (Dog) (VBO_0200015), Beagle (Dog) (VBO_0200131), English Springer Spaniel (Dog) (VBO_0200497), Portuguese Water Dog (Dog) (VBO_0201077), Shiba Inu (Dog) (VBO_0201220).
Breeds in which the phene has been documented. (If a likely causal variant has been documented for the phene, see the variant table breeds in which the variant has been reported).

Associated gene: