Tay-Sachs disease is a progressive neurodegenerative disease.  Its clinical manifestations range from progressive neurodegeneration beginning at 3-6 months old and death before the age of 4 to variable neurological findings in the adult onset variant.  This disease is caused by an autosomal recessively inherited deficiency of a lysosomal enzyme, HEX A.  There are two subunits, α and β, that are encoded by the HEX A gene.  Tay-Sachs and its variants are caused by defects in the α subunit induced by mutations of the HEX A gene.

To date there is no effective treatment or cure for Tay-Sachs.  Some therapeutic approaches for lysosomal storage disease include bone marrow transplantation, enzyme replacement, and chaperone and gene therapy. However, research into treatments for Tay-Sachs have hit a wall because there are not any animal models that present with this disease.  Potential treatments must first show efficacy in animal models prior to human applications.  Dogs, cats, mice, deer, and swine have been reported to suffer from the same excessive lysosomal storage in neuronal cells as people who suffer from Tay-Sachs, but most of the diseases in these animals are due to deficiencies in the β subunit of the HEX A gene.

Fortunately, two cases involving American flamingoes have given researchers hope for finding an animal model that is suitable for this disease.  A 6 week old female flamingo and a 5 month old old flamingo male, both being housed at zoological institutions, were presenting with symptoms of a neurological disorder.  The flamingoes showed lethargy, unwillingness to eat, abnormal head positioning and movement, ataxia, and finally they were unable to stand.  Both animals were humanely euthanized.  Upon necropsy the brain of the male flamingo showed foamy, cytoplasmic vacuolation and expansion of the cerebellar Purkinje cells, cerebral neurons, and astrocytes.  Staining of the cytoplasmic material suggested a defect in lipid degradation.  Similar changes were seen in the retinal ganglion cells, as well as peripheral nerve ganglia and plexuses.flamingo

After the researchers concluded that both flamingoes died of a neurodegenerative disease that affected lipid degradation they did some tests on the genes of these animals to see if they are an appropriate model for Tay-Sachs disease.  They found that the flamingo cDNA for the hexa gene is 72.6% homologous to the same gene in humans.  They also found similar enzymatic activities between the flamingo and human gene, and that the flamingo carries a conserved region in the hexa gene that is also carried in the human HEX A gene.

These findings have led researchers one step closer to understanding Tay-Sachs disease and possible future treatments.  More research is currently being done to assess whether the American Flamingo is an appropriate model to use for Tay-Sachs treatment research.

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