Marika Salvalaio

Genistein reduces glycosaminoglycan levels in a mouse model of mucopolysaccharidosis type II.

Background and purpose:  Mucopolysaccharidoses (MPS) are lysosomal storage disorders resulting from a deficit of specific lysosomal enzymes catalysing glycosaminoglycan (GAG) degradation. The typical pathology involves most of the organ systems, including the brain, in its severe forms. The soy isoflavone genistein has recently attracted considerable attention as it can reduce GAG synthesis in vitro. Furthermore, genistein is able to cross the blood–brain barrier in the rat. The present study was undertaken to assess the ability of genistein to reduce urinary and tissue GAG levels in vivo.

Glucocerebrosidase deficiency in zebrafish affects primary bone ossification through increased oxidative stress and reduced Wnt/β-catenin signaling

Loss of lysosomal glucocerebrosidase (GBA1) function is responsible for several organ defects, including skeletal abnormalities in type 1 Gaucher disease (GD). Enhanced bone resorption by infiltrating macrophages has been proposed to lead to major bone defects. However, while more recent evidences support the hypothesis that osteoblastic bone formation is impaired, a clear pathogenetic mechanism has not been depicted yet. Here, by combining different molecular approaches, we show that Gba1 loss of function in zebrafish is associated with defective canonical Wnt signaling, impaired osteoblast differentiation and reduced bone mineralization. We also provide evidence that increased reactive oxygen species production precedes the Wnt signaling impairment, which can be reversed upon human GBA1 overexpression. Type 1 GD patient fibroblasts similarly exhibit reduced Wnt signaling activity, as a consequence of increased β-catenin degradation. Our results support a novel model in which a primary defect in canonical Wnt signaling antecedes bone defects in type 1 GD.

Perturbations in cell signaling elicit early cardiac defects in mucopolysaccharidosis type II

&NA; Morphogens release and activity can be negatively affected by an impaired glycosaminoglycans (GAGs) turnover and proteoglycans assembly in the extracellular matrix, leading to altered tissue morphogenesis. In this work, we show that loss of Iduronate‐2‐sulfatase (IDS) activity, affecting GAGs catabolism and responsible for a life‐threatening valvulopathy in mucopolysaccharidosis type II (MPSII), triggers early Sonic Hedgehog (Shh) and Wnt/&bgr;‐catenin signaling defects, leading to aberrant heart development and atrioventricular valve formation in a zebrafish model. In addition, we consistently found impaired Shh signaling activity and cardiac electrophysiological abnormalities in IDS knockout mice at postnatal stages before any evident massive GAGs accumulation. These results suggest that IDS activity substantially affect cardiac morphogenesis through impaired Shh signaling and document an unexplored role of the enzyme in the fine‐tuning of cell signaling pathways.

FGF signaling deregulation is associated with early developmental skeletal defects in animal models for mucopolysaccharidosis type II (MPSII)

Skeletal abnormalities represent a major clinical burden in patients affected by the lysosomal storage disorder mucopolysaccharidosis type II (MPSII, OMIM #309900). While extensive research has emphasized the detrimental role of stored glycosaminoglycans (GAGs) in the bone marrow (BM), a limited understanding of primary cellular mechanisms underlying bone defects in MPSII has hampered the development of bone-targeted therapeutic strategies beyond enzyme replacement therapy (ERT). We here investigated the involvement of key signaling pathways related to the loss of iduronate-2-sulfatase activity in two different MPSII animal models, D. rerio and M. musculus. We found that FGF pathway activity is impaired during early stages of bone development in IDS knockout mice and in a newly generated Ids mutant fish. In both models the FGF signaling deregulation anticipated a slow but progressive defect in bone differentiation, regardless of any extensive GAGs storage. We also show that MPSII patient fibroblasts harboring different mutations spanning the IDS gene exhibit perturbed FGF signaling-related markers expression. Our work opens a new venue to discover possible druggable novel key targets in MPSII.

Brain RNA-seq profiling of the mucopolysaccharidosis type II mouse model

Lysosomal storage disorders (LSDs) are a group of about 50 genetic metabolic disorders, mainly affecting children, sharing the inability to degrade specific endolysosomal substrates. This results in failure of cellular functions in many organs, including brain that in most patients may go through progressive neurodegeneration. In this study, we analyzed the brain of the mouse model for Hunter syndrome, a LSD mostly presenting with neurological involvement. Whole transcriptome analysis of the cerebral cortex and midbrain/diencephalon/hippocampus areas was performed through RNA-seq. Genes known to be involved in several neurological functions showed a significant differential expression in the animal model for the disease compared to wild type. Among the pathways altered in both areas, axon guidance, calcium homeostasis, synapse and neuroactive ligand–receptor interaction, circadian rhythm, neuroinflammation and Wnt signaling were the most significant. Application of RNA sequencing to dissect pathogenic alterations of complex syndromes allows to photograph perturbations, both determining and determined by these disorders, which could simultaneously occur in several metabolic and biochemical pathways. Results also emphasize the common, altered pathways between neurodegenerative disorders affecting elderly and those associated with pediatric diseases of genetic origin, perhaps pointing out a general common course for neurodegeneration, independent from the primary triggering cause.