Abstract Mucopolysaccharidosis (MPS) IIIB, also known as Sanfilippo Syndrome B, is a devastating childhood disease. Unfortunately, there are currently no available treatments for MPS IIIB patients. Yet, animal models of lysosomal storage diseases have been valuable tools in identifying promising avenues of treatment. Enzyme replacement therapy, gene therapy, and bone marrow transplant have all shown efficacy in the MPS IIIB model systems. A ubiquitous finding across rodent models of lysosomal storage diseases is that the best treatment outcomes resulted from intervention prior to symptom onset. Therefore, the aim of the current study was to identify early markers of disease progression in the MPS IIIB mouse model as well as examine clinically-relevant behavioral domains not yet explored in this model. We observed reduced maternal isolation-induced ultrasonic vocalizations in MPS IIIB mice relative to controls, as well as disruption in a number of the spectrotemporal features. MPS IIIB also exhibited disrupted thermoregulation during the first two postnatal weeks without any differences in body weight. The developmental trajectories of gait were largely normal. In early adulthood, we observed intact visual acuity and sociability yet a more submissive phenotype and increased aggressive behavior relative to controls. MPS IIIB mice showed greater inhibition of startle in response to a pretone with a decrease in overall startle response and reduced cued fear memory. MPS IIIB also weighed significantly more than controls throughout adulthood and showed larger whole brain volumes and normalized regional volumes with intact tissue integrity as measured with magnetic resonance and diffusion tensor imaging, respectively. Together, these results indicate disease markers are present as early as the first two weeks postnatal in this model. Further, this model recapitulates social, sensory and fear-related clinical features. Our study using a mouse model of MPS IIIB provides essential baseline information that will be useful in future evaluations of potential treatments.
The immune response to exogenous protein has been shown to reduce therapeutic efficacy in animal models of enzyme replacement therapy. A previously published study demonstrated an immunosuppressive regimen which successfully induced immune tolerance to α-L-iduronidase in canines with mucopolysaccharidosis I. The two key requirements for success were high-affinity receptor-mediated enzyme uptake, conferred by mannose 6-phosphate conjugation, and immunosuppression with low-dose antigen exposure. In this study, we attempted to induce immune tolerance to phenylalanine ammonia-lyase by producing a recombinant mannose 6-phosphate conjugated form and administering it to normal dogs according to the previously published tolerance induction regimen. We found that the recombinant conjugated enzyme was stable, could bind to the mannose 6-phosphate receptor with high affinity, and its uptake into fibroblast cells was mediated by this receptor. However, at the end of a tolerance induction period, all dogs demonstrated an antigen-specific immune response when challenged with increasing doses of unconjugated phenylalanine ammonia-lyase. The average time to seroconvert was not significantly different among three separate groups of test animals (n = 3 per group) and was not significantly different from one group of control animals (n = 3). None of the nine test group animals developed immune tolerance to the enzyme using this method. This suggests that high-affinity cellular uptake mediated by the mannose 6-phosphate receptor combined with a previously studied tolerizing regimen is not sufficient to induce immune tolerance to an exogenous protein and that other factors affecting antigen distribution, uptake, and presentation are likely to be important.
Abstract Background Short tandem repeats (STRs) are widely distributed across the human genome and are associated with numerous neurological disorders. However, the extent that STRs contribute to disease is likely under-estimated because of the challenges calling these variants in short read next generation sequencing data. Several computational tools have been developed for STR variant calling, but none fully address all of the complexities associated with this variant class. Results Here we introduce LUSTR which is designed to address some of the challenges associated with STR variant calling by enabling more flexibility in defining STR loci, allowing for customizable modules to tailor analyses, and expanding the capability to call somatic and multiallelic STR variants. LUSTR is a user-friendly and easily customizable tool for targeted or unbiased genome-wide STR variant screening that can use either predefined or novel genome builds. Using both simulated and real data sets, we demonstrated that LUSTR accurately infers germline and somatic STR expansions in individuals with and without diseases. Conclusions LUSTR offers a powerful and user-friendly approach that allows for the identification of STR variants and can facilitate more comprehensive studies evaluating the role of pathogenic STR variants across human diseases.
