Diagnosis, Surveillance and Management of Streptococcus equi subspecies zooepidemicus Infections in Chinchillas (Chinchilla lanigera).

During a 6-mo period, two 5-6 mo old female chinchillas (Chinchilla lanigera) were examined at the University of Colorado Anschutz Medical Campus after the discovery of firm, nonmobile masses in the left ventral cervical and left axillary region. Other than these findings and mild weight loss, both chinchillas' physical exams were normal. Bloodwork revealed an inflammatory leukogram characterized by leukocytosis, toxic neutrophils, lymphopenia, and monocytosis with mild, nonregenerative anemia. At necropsy, both masses were identified as abscesses. Streptococcus equi, subspecies zooepidemicus (S. zooepidemicus) was isolated in pure culture. Histology of the lungs, liver, spleen, and kidneys showed a marked increase in the numbers of both polymorphonuclear leukocytes and lymphocytes. Both animals were deemed unsuitable for research and were euthanized under isoflurane anesthesia by an intracardiac injection of pentobarbital sodium solution. S. zooepidemicus is an opportunistic, commensal organism found in the upper respiratory tract of horses. This organism has been documented to cause disease in other species and is zoonotic. Infections in humans have been reported, resulting in glomerulonephritis, endocarditis, septic arthritis, osteomyelitis, meningitis, and death. To aid in diagnosis and prospective surveillance of this bacteria, oral and nasal swabs were collected from the remaining cohort of chinchillas, and a qPCR screening assay was implemented. Within 12 mo, 4 of 41 additional females tested positive by culture or qPCR, resulting in a disease prevalence of 14% (6 of 43). However, only 2 of the additional 4 S. zooepidemicus positive animals developed clinical signs. The potential for the spread of infection, zoonosis, and adverse effects on research demonstrate that surveillance for S. zooepidemicus should be considered in a biomedical research environment.

Serine 776 of ataxin-1 is critical for polyglutamine-induced disease in SCA1 transgenic mice.

Polyglutamine-induced neurodegeneration in transgenic mice carrying the spinocerebellar ataxia type 1 (SCA1) gene is modulated by subcellular distribution of ataxin-1 and by components of the protein folding/degradation machinery. Since phosphorylation is a prominent mechanism by which these processes are regulated, we examined phosphorylation of ataxin-1 and found that serine 776 (S776) was phosphorylated. Residue 776 appeared to affect cellular deposition of ataxin-1[82Q] in that ataxin-1[82Q]-A776 failed to form nuclear inclusions in tissue culture cells. The importance of S776 for polyglutamine-induced pathogenesis was examined by generating ataxin-1[82Q]-A776 transgenic mice. These mice expressed ataxin-1[82Q]-A776 within Purkinje cell nuclei, yet the ability of ataxin-1[82Q]-A776 to induce disease was substantially reduced. These studies demonstrate that polyglutamine tract expansion and localization of ataxin-1 to the nucleus of Purkinje cells are not sufficient to induce disease. We suggest that S776 of ataxin-1 also has a critical role in SCA1 pathogenesis.

A cell-based screen for modulators of ataxin-1 phosphorylation.

Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant neurodegenerative disorder caused by the expansion of a glutamine repeat within the SCA1-encoded protein ataxin-1. We have previously shown that serine 776 (S776) of both wild-type and mutant ataxin-1 is phosphorylated in vivo and in vitro. Moreover, preventing phosphorylation of this residue by replacing it with alanine resulted in a mutant protein, which was not pathogenic in spite of its nuclear localization. To further investigate pathways leading to S776 phosphorylation of ataxin-1, we developed a cell-culture based assay to screen for modulators of S776 phosphorylation. In this assay, ataxin-1 expression was monitored by enhanced green fluorescent protein (EGFP) fluorescence in cell lines stably expressing EGFP-ataxin-1 fusion protein. The phospho-S776 ataxin-1 specific antibody (PN1168) was used to assess ataxin-1 S776 phosphorylation. A library of 84 known kinase and phosphatase inhibitors was screened. Analysis of the list of drugs that modified S776 phosphorylation places many of the inhibited kinases into known cell signaling pathways. A pathway associated with calcium signaling resulted in phosphorylation of both wild-type and mutant ataxin-1. Interestingly, inhibitors of the PI3K/Akt pathway predominantly diminished mutant ataxin-1 phosphorylation. These results provide new molecular tools to aid in elucidating the biological role of ataxin-1 phosphorylation and perhaps provide potential leads toward the development of a therapy for SCA1.

Gene profiling links SCA1 pathophysiology to glutamate signaling in Purkinje cells of transgenic mice.

Spinocerebellar ataxia type 1 (SCA1) is a neurodegenerative disease caused by the expansion of a polyglutamine repeat within the disease protein, ataxin 1. To elucidate cellular pathways involved in SCA1, we used DNA microarrays to determine the pattern of gene expression in SCA1 transgenic mice at two specific times in the disease process; 5 weeks, a timepoint prior to onset of pathology, and 12 weeks, at the midpoint of the disease progression. Taking advantage of the availability of three SCA1 transgenic mouse lines, each expressing a different form of ataxin-1, we utilized a strategy that resulted in the identification of a limited number of genes with an altered pattern of expression specific to the development of disease. By comparing the pattern of gene expression in the SCA1 ataxic B05-ataxin-1[82Q] transgenic mouse line with those seen in two non-ataxic lines, A02-ataxin-1[30Q] and K772T-[82Q], nine genes were identified whose expression was consistently altered in the cerebellum of B05[82Q] mice at 5 and 12 weeks of age. Interestingly, five of the genes in this group form a biological cohort centered on glutamate signaling pathways in Purkinje cells.