Characterization of early neuroinflammatory cues in a zebrafish model of Mucopolysaccharidosis type II

Mucopolysaccharidosis type II (MPS II or Hunter syndrome) is a rare X-linked recessive lysosomal storage disease (LSD) caused by mutations of iduronate-2-sulfatase (IDS), a lysosomal enzyme involved in the first step of heparan sulfate (HS) and dermatan sulfate (DS) degradation. This results in glycosaminoglycans accumulation in nearly all cell types leading to a huge spectrum of clinical manifestations including severe airway obstruction, skeletal deformities, cardiomyopathy and in most patients neurological decline. In particular, the central nervous system (CNS) has been demonstrated extremely vulnerable to impaired lysosomal function. Indeed, several LSDs exhibit neuropathological manifestations, including prominent microglial and astrocyte activation and neuroinflammation. Astrocytes, the most abundant cell type in the brain, fulfill several homeostatic functions but also participate in neuroinflammatory responses through their massive secretion of various chemokines. Upon activation, astrocytes (also referred as “reactive”) undergo a morphological transformation marked by increased intermediate filament expression, i.e., glial fibrillary acidic protein (GFAP) and vimentin. Accordingly, the aim of my research has been to evaluate by western blot analysis the levels of Gfap in the stable ids mutant zebrafish line (herein referred as ids-/-). Indeed, Gfap is a universally recognized marker for astroglial cells, and its increase has been previously associated with a neuroinflammatory condition. Furthermore, I aimed to define the relation between astrocyte activation and cell death in the brain of ids mutant fish. I also carried out a preliminary characterization of ids mutants for microglial, oxidative stress and autophagy-related markers to verify the onset of additional pathological changes together with astrogliosis. To conclude, I applied a behavioral assay to assess whether the zebrafish MPS II model develops an anxiolytic-like phenotype. My preliminary results allowed me to define the first signs of neuroinflammation in a very early life stage of ids mutant fish, pointing out that the onset of astrogliosis is concurrent with dysfunctional key cellular processes, each contributing to disease pathophysiology.