Striking and widespread microglial activation in the brains of Southdown lambs with type II glucocerebrosidosis (neuronopathic Gaucher disease)

Glucocerebrosidosis (termed Gaucher disease in humans) is a lysosomal storage disease, caused by a deficiency of the enzyme glucocerebrosidase, which results in accumulation of the glycolipid substrate glucocerebroside in the macrophage–monocyte system. Three principal forms are recognized in humans, two being neuronopathic and resulting in neurodegeneration. Only two spontaneously arising cases have been described in domestic animals, one in a dog and the other in a flock of Southdown sheep. Since microglial activation is increasingly being recognized as having an important role in the pathogenesis of Gaucher disease and archival brains were available from lambs with type II glucocerebrosidosis, we wanted to determine whether microglia were activated in these brains. Ionized calcium binding adaptor molecule 1 (Iba1), a specific and the most widely expressed immunohistochemical marker of microglial activation, was used. Striking and widely distributed activation of microglia was demonstrated, suggesting that microglia actively participate in the development of neuropathological changes in ovine Gaucher disease. This aspect of Gaucher disease requires further study in any future cases detected in domestic animal species, including the mechanism by which this markedly increased Iba1 expression is related to disease progression.