A MOUSE MODEL FOR THE HUMAN LYSOSOMAL DISEASE ASPARTYLGLYCOSAMINURIA

Aspartylglycosaminuria (AGU), the most common disorder of glycoprotein degradation in humans, is caused by mutations in the gene encoding th e lysosomal enzyme glycosylasparaginase (Aga)(1). The resulting enzyme deficiency allows aspartylglucosamine (GlcNAc-Asn) and other glycoasp aragines to accumulate in tissues and body fluids, from early fetal li fe onward(1). The clinical course is characterized by normal early dev elopment, slowly progressing to severe mental and motor retardation in early adulthood(2,3). The exact pathogenesis of AGU in humans is unkn own and neither therapy nor an animal model for this debilitating and ultimately fatal disease exists. Through targeted disruption of the mo use Ago gene in embryonic stem cells, we generated mice that completel y lack Aga activity. At the age of 5-10 months a massive accumulation of GlcNAc-Asn was detected along with lysosomal vacuolization, axonal swelling in the gracile nucleus and impaired neuromotor coordination. A significant number of older male mice had massively swollen bladders , which was not caused by obstruction, but most likely related to the impaired function of the nervous system. These findings are consistent with the pathogenesis of AGU and provide further data explaining the impaired neurological function in AGU patients.