An orthotopic syngeneic mouse model of bortezomib-resistant multiple myeloma.

While bortezomib has significant benefits in multiple myeloma (MM) therapy, the disease remains incurable due to the invariable development of bortezomib resistance. This emphasises the need for advanced models for preclinical evaluation of new therapeutic approaches for bortezomib-resistant MM. Here, we describe the development of an orthotopic syngeneic bortezomib-resistant MM mouse model based on the most well-characterised syngeneic MM mouse model derived from spontaneous MM-forming C57BL/KaLwRij mice. Using bortezomib-resistant 5TGM1 cells, we report and characterise a robust syngeneic mouse model of bortezomib-resistant MM that is well suited to the evaluation of new therapeutic approaches for proteasome inhibitor-resistant MM.

GD2-targeting CAR-T cells enhanced by transgenic IL-15 expression are an effective and clinically feasible therapy for glioblastoma.

BACKGROUND: Aggressive primary brain tumors such as glioblastoma are uniquely challenging to treat. The intracranial location poses barriers to therapy, and the potential for severe toxicity. Effective treatments for primary brain tumors are limited, and 5-year survival rates remain poor. Immune checkpoint inhibitor therapy has transformed treatment of some other cancers but has yet to significantly benefit patients with glioblastoma. Early phase trials of chimeric antigen receptor (CAR) T-cell therapy in patients with glioblastoma have demonstrated that this approach is safe and feasible, but with limited evidence of its effectiveness. The choices of appropriate target antigens for CAR-T-cell therapy also remain limited. METHODS: We profiled an extensive biobank of patients' biopsy tissues and patient-derived early passage glioma neural stem cell lines for GD2 expression using immunomicroscopy and flow cytometry. We then employed an approved clinical manufacturing process to make CAR- T cells from patients with peripheral blood of glioblastoma and diffuse midline glioma and characterized their phenotype and function in vitro. Finally, we tested intravenously administered CAR-T cells in an aggressive intracranial xenograft model of glioblastoma and used multicolor flow cytometry, multicolor whole-tissue immunofluorescence and next-generation RNA sequencing to uncover markers associated with effective tumor control. RESULTS: Here we show that the tumor-associated antigen GD2 is highly and consistently expressed in primary glioblastoma tissue removed at surgery. Moreover, despite patients with glioblastoma having perturbations in their immune system, highly functional GD2-specific CAR-T cells can be produced from their peripheral T cells using an approved clinical manufacturing process. Finally, after intravenous administration, GD2-CAR-T cells effectively infiltrated the brain and controlled tumor growth in an aggressive orthotopic xenograft model of glioblastoma. Tumor control was further improved using CAR-T cells manufactured with a clinical retroviral vector encoding an interleukin-15 transgene alongside the GD2-specific CAR. These CAR-T cells achieved a striking 50% complete response rate by bioluminescence imaging in established intracranial tumors. CONCLUSIONS: Targeting GD2 using a clinically deployed CAR-T-cell therapy has a sound scientific and clinical rationale as a treatment for glioblastoma and other aggressive primary brain tumors.

Ceramide-induced integrated stress response overcomes Bcl-2 inhibitor resistance in acute myeloid leukemia.

Inducing cell death by the sphingolipid ceramide is a potential anticancer strategy, but the underlying mechanisms remain poorly defined. In this study, triggering an accumulation of ceramide in acute myeloid leukemia (AML) cells by inhibition of sphingosine kinase induced an apoptotic integrated stress response (ISR) through protein kinase R-mediated activation of the master transcription factor ATF4. This effect led to transcription of the BH3-only protein Noxa and degradation of the prosurvival Mcl-1 protein on which AML cells are highly dependent for survival. Targeting this novel ISR pathway, in combination with the Bcl-2 inhibitor venetoclax, synergistically killed primary AML blasts, including those with venetoclax-resistant mutations, as well as immunophenotypic leukemic stem cells, and reduced leukemic engraftment in patient-derived AML xenografts. Collectively, these findings provide mechanistic insight into the anticancer effects of ceramide and preclinical evidence for new approaches to augment Bcl-2 inhibition in the therapy of AML and other cancers with high Mcl-1 dependency.

Resensitising proteasome inhibitor-resistant myeloma with sphingosine kinase 2 inhibition.

The introduction of the proteasome inhibitor bortezomib into treatment regimens for myeloma has led to substantial improvement in patient survival. However, whilst bortezomib elicits initial responses in many myeloma patients, this haematological malignancy remains incurable due to the development of acquired bortezomib resistance. With other patients presenting with disease that is intrinsically bortezomib resistant, it is clear that new therapeutic approaches are desperately required to target bortezomib-resistant myeloma. We have previously shown that targeting sphingolipid metabolism with the sphingosine kinase 2 (SK2) inhibitor K145 in combination with bortezomib induces synergistic death of bortezomib-naïve myeloma. In the current study, we have demonstrated that targeting sphingolipid metabolism with K145 synergises with bortezomib and effectively resensitises bortezomib-resistant myeloma to this proteasome inhibitor. Notably, these effects were dependent on enhanced activation of the unfolded protein response, and were observed in numerous separate myeloma models that appear to have different mechanisms of bortezomib resistance, including a new bortezomib-resistant myeloma model we describe which possesses a clinically relevant proteasome mutation. Furthermore, K145 also displayed synergy with the next-generation proteasome inhibitor carfilzomib in bortezomib-resistant and carfilzomib-resistant myeloma cells. Together, these findings indicate that targeting sphingolipid metabolism via SK2 inhibition may be effective in combination with a broad spectrum of proteasome inhibitors in the proteasome inhibitor resistant setting, and is an approach worth clinical exploration.

Mechanotransduction activates RhoA in the neighbors of apoptotic epithelial cells to engage apical extrusion.

Epithelia must eliminate apoptotic cells to preserve tissue barriers and prevent inflammation.1 Several different mechanisms exist for apoptotic clearance, including efferocytosis2,3 and apical extrusion.4,5 We found that extrusion was the first-line response to apoptosis in cultured monolayers and in zebrafish epidermis. During extrusion, the apoptotic cell elicited active lamellipodial protrusions and assembly of a contractile extrusion ring in its neighbors. Depleting E-cadherin compromised both the contractile ring and extrusion, implying that a cadherin-dependent pathway allows apoptotic cells to engage their neighbors for extrusion. We identify RhoA as the cadherin-dependent signal in the neighbor cells and show that it is activated in response to contractile tension from the apoptotic cell. This mechanical stimulus is conveyed by a myosin-VI-dependent mechanotransduction pathway that is necessary both for extrusion and to preserve the epithelial barrier when apoptosis was stimulated. Earlier studies suggested that release of sphingosine-1-phosphate (S1P) from apoptotic cells might define where RhoA was activated. However, we found that, although S1P is necessary for extrusion, its contribution does not require a localized source of S1P in the epithelium. We therefore propose a unified view of how RhoA is stimulated to engage neighbor cells for apoptotic extrusion. Here, tension-sensitive mechanotransduction is the proximate mechanism that activates RhoA specifically in the immediate neighbors of apoptotic cells, but this also must be primed by S1P in the tissue environment. Together, these elements provide a coincidence detection system that confers robustness on the extrusion response.

Cytoplasmic dynein regulates the subcellular localization of sphingosine kinase 2 to elicit tumor-suppressive functions in glioblastoma.

While the two mammalian sphingosine kinases, SK1 and SK2, both catalyze the generation of pro-survival sphingosine 1-phosphate (S1P), their roles vary dependent on their different subcellular localization. SK1 is generally found in the cytoplasm or at the plasma membrane where it can promote cell proliferation and survival. SK2 can be present at the plasma membrane where it appears to have a similar function to SK1, but can also be localized to the nucleus, endoplasmic reticulum or mitochondria where it mediates cell death. Although SK2 has been implicated in cancer initiation and progression, the mechanisms regulating SK2 subcellular localization are undefined. Here, we report that SK2 interacts with the intermediate chain subunits of the retrograde-directed transport motor complex, cytoplasmic dynein 1 (DYNC1I1 and -2), and we show that this interaction, particularly with DYNC1I1, facilitates the transport of SK2 away from the plasma membrane. DYNC1I1 is dramatically downregulated in patient samples of glioblastoma (GBM), where lower expression of DYNC1I1 correlates with poorer patient survival. Notably, low DYNC1I1 expression in GBM cells coincided with more SK2 localized to the plasma membrane, where it has been recently implicated in oncogenesis. Re-expression of DYNC1I1 reduced plasma membrane-localized SK2 and extracellular S1P formation, and decreased GBM tumor growth and tumor-associated angiogenesis in vivo. Consistent with this, chemical inhibition of SK2 reduced the viability of patient-derived GBM cells in vitro and decreased GBM tumor growth in vivo. Thus, these findings demonstrate a tumor-suppressive function of DYNC1I1, and uncover new mechanistic insights into SK2 regulation which may have implications in targeting this enzyme as a therapeutic strategy in GBM.

CIB2 Negatively Regulates Oncogenic Signaling in Ovarian Cancer via Sphingosine Kinase 1.

Sphingosine kinase 1 (SK1) is a key regulator of the cellular balance between proapoptotic and prosurvival sphingolipids. Oncogenic signaling by SK1 relies on its localization to the plasma membrane, which is mediated by the calcium and integrin binding protein CIB1 via its Ca2+-myristoyl switch function. Here we show that another member of the CIB family, CIB2, plays a surprisingly opposite role to CIB1 in the regulation of SK1 signaling. CIB2 bound SK1 on the same site as CIB1, yet it lacks the Ca2+-myristoyl switch function. As a result, CIB2 blocked translocation of SK1 to the plasma membrane and inhibited its subsequent signaling, which included sensitization to TNFα-induced apoptosis and inhibition of Ras-induced neoplastic transformation. CIB2 was significantly downregulated in ovarian cancer and low CIB2 expression was associated with poor prognosis in ovarian cancer patients. Notably, reintroduction of CIB2 in ovarian cancer cells blocked plasma membrane localization of endogenous SK1, reduced in vitro neoplastic growth and tumor growth in mice, and suppressed cell motility and invasiveness both in vitro and in vivo Consistent with the in vitro synergistic effects between the SK1-specific inhibitor SK1-I and standard chemotherapeutics, expression of CIB2 also sensitized ovarian cancer cells to carboplatin. Together, these findings identify CIB2 as a novel endogenous suppressor of SK1 signaling and potential prognostic marker and demonstrate the therapeutic potential of SK1 in this gynecologic malignancy. Cancer Res; 77(18); 4823-34. ©2017 AACR.

An oncogenic role for sphingosine kinase 2.

While both human sphingosine kinases (SK1 and SK2) catalyze the generation of the pleiotropic signaling lipid sphingosine 1-phosphate, these enzymes appear to be functionally distinct. SK1 has well described roles in promoting cell survival, proliferation and neoplastic transformation. The roles of SK2, and its contribution to cancer, however, are much less clear. Some studies have suggested an anti-proliferative/pro-apoptotic function for SK2, while others indicate it has a pro-survival role and its inhibition can have anti-cancer effects. Our analysis of gene expression data revealed that SK2 is upregulated in many human cancers, but only to a small extent (up to 2.5-fold over normal tissue). Based on these findings, we examined the effect of different levels of cellular SK2 and showed that high-level overexpression reduced cell proliferation and survival, and increased cellular ceramide levels. In contrast, however, low-level SK2 overexpression promoted cell survival and proliferation, and induced neoplastic transformation in vivo. These findings coincided with decreased nuclear localization and increased plasma membrane localization of SK2, as well as increases in extracellular S1P formation. Hence, we have shown for the first time that SK2 can have a direct role in promoting oncogenesis, supporting the use of SK2-specific inhibitors as anti-cancer agents.

Reduction in sphingosine kinase 1 influences the susceptibility to dengue virus infection by altering antiviral responses.

Sphingosine kinase (SK) 1 is a host kinase that enhances some viral infections. Here we investigated the ability of SK1 to modulate dengue virus (DENV) infection in vitro. Overexpression of SK1 did not alter DENV infection; however, targeting SK1 through chemical inhibition resulted in reduced DENV RNA and infectious virus release. DENV infection of SK1⁻/ ⁻ murine embryonic fibroblasts (MEFs) resulted in inhibition of infection in an immortalized line (iMEF) but enhanced infection in primary MEFs (1°MEFs). Global cellular gene expression profiles showed expected innate immune mRNA changes in DENV-infected WT but no induction of these responses in SK1⁻/⁻ iMEFs. Reverse transciption PCR demonstrated a low-level induction of IFN-ß and poor induction of mRNA for the interferon-stimulated genes (ISGs) viperin, IFIT1 and CXCL10 in DENV-infected SK1⁻/⁻ compared with WT iMEFs. Similarly, reduced induction of ISGs was observed in SK1⁻/⁻ 1°MEFs, even in the face of high-level DENV replication. In both iMEFs and 1°MEFs, DENV infection induced production of IFN-ß protein. Additionally, higher basal levels of antiviral factors (IRF7, CXCL10 and OAS1) were observed in uninfected SK1⁻/⁻ iMEFs but not 1°MEFs. This suggests that, in this single iMEF line, lack of SK1 upregulates the basal levels of factors that may protect cells against DENV infection. More importantly, regardless of the levels of DENV replication, all cells that lacked SK1 produced IFN-ß but were refractory to induction of ISGs such as viperin, IFIT1 and CXCL10. Based on these findings, we propose new roles for SK1 in affecting innate responses that regulate susceptibility to DENV infection.

Sphingosine 1-phosphate is a ligand for peroxisome proliferator-activated receptor-γ that regulates neoangiogenesis.

Sphingosine 1-phosphate (S1P) is a bioactive lipid that can function both extracellularly and intracellularly to mediate a variety of cellular processes. Using lipid affinity matrices and a radiolabeled lipid binding assay, we reveal that S1P directly interacts with the transcription factor peroxisome proliferator-activated receptor (PPAR)γ. Herein, we show that S1P treatment of human endothelial cells (ECs) activated a luciferase-tagged PPARγ-specific gene reporter by ∼12-fold, independent of the S1P receptors. More specifically, in silico docking, gene reporter, and binding assays revealed that His323 of the PPARγ ligand binding domain is important for binding to S1P. PPARγ functions when associated with coregulatory proteins, and herein we identify that peroxisome proliferator-activated receptor-γ coactivator 1 (PGC1)ß binds to PPARγ in ECs and their progenitors (nonadherent endothelial forming cells) and that the formation of this PPARγ:PGC1ß complex is increased in response to S1P. ECs treated with S1P selectively regulated known PPARγ target genes with PGC1ß and plasminogen-activated inhibitor-1 being increased, no change to adipocyte fatty acid binding protein 2 and suppression of CD36. S1P-induced in vitro tube formation was significantly attenuated in the presence of the PPARγ antagonist GW9662, and in vivo application of GW9662 also reduced vascular development in Matrigel plugs. Interestingly, activation of PPARγ by the synthetic ligand troglitazone also reduced tube formation in vitro and in vivo. To support this, Sphk1(-/-)Sphk2(+/-) mice, with low circulating S1P levels, demonstrated a similar reduction in vascular development. Taken together, our data reveal that the transcription factor, PPARγ, is a bona fide intracellular target for S1P and thus suggest that the S1P:PPARγ:PGC1ß complex may be a useful target to manipulate neovascularization.

A selective ATP-competitive sphingosine kinase inhibitor demonstrates anti-cancer properties.

The dynamic balance of cellular sphingolipids, the sphingolipid rheostat, is an important determinant of cell fate, and is commonly deregulated in cancer. Sphingosine 1-phosphate is a signaling molecule with anti-apoptotic, pro-proliferative and pro-angiogenic effects, while conversely, ceramide and sphingosine are pro-apoptotic. The sphingosine kinases (SKs) are key regulators of this sphingolipid rheostat, and are attractive targets for anti-cancer therapy. Here we report a first-in-class ATP-binding site-directed small molecule SK inhibitor, MP-A08, discovered using an approach of structural homology modelling of the ATP-binding site of SK1 and in silico docking with small molecule libraries. MP-A08 is a highly selective ATP competitive SK inhibitor that targets both SK1 and SK2. MP-A08 blocks pro-proliferative signalling pathways, induces mitochondrial-associated apoptosis in a SK-dependent manner, and reduces the growth of human lung adenocarcinoma tumours in a mouse xenograft model by both inducing tumour cell apoptosis and inhibiting tumour angiogenesis. Thus, this selective ATP competitive SK inhibitor provides a promising candidate for potential development as an anti-cancer therapy, and also, due to its different mode of inhibition to other known SK inhibitors, both validates the SKs as targets for anti-cancer therapy, and represents an important experimental tool to study these enzymes.

Independent trafficking of the KCNQ1 K+ channel and H+-K+-ATPase in gastric parietal cells from mice.

Gastric acid secretion by the H(+)-K(+)-ATPase at the apical surface of activated parietal cells requires luminal K(+) provided by the KCNQ1/KCNE2 K(+) channel. However, little is known about the trafficking and relative spatial distribution of KCNQ1 and H(+)-K(+)-ATPase in resting and activated parietal cells and the capacity of KCNQ1 to control acid secretion. Here we show that inhibition of KCNQ1 activity quickly curtails gastric acid secretion in vivo, even when the H(+)-K(+)-ATPase is permanently anchored in the apical membrane, demonstrating a key role of the K(+) channel in controlling acid secretion. Three-dimensional imaging analysis of isolated mouse gastric units revealed that the majority of KCNQ1 resides in an intracytoplasmic, Rab11-positive compartment in resting parietal cells, distinct from H(+)-K(+)-ATPase-enriched tubulovesicles. Upon activation, there was a significant redistribution of H(+)-K(+)-ATPase and KCNQ1 from intracytoplasmic compartments to the apical secretory canaliculi. Significantly, high Förster resonance energy transfer was detected between H(+)-K(+)-ATPase and KCNQ1 in activated, but not resting, parietal cells. These findings demonstrate that H(+)-K(+)-ATPase and KCNQ1 reside in independent intracytoplasmic membrane compartments, or membrane domains, and upon activation of parietal cells, both membrane proteins are transported, possibly via Rab11-positive recycling endosomes, to apical membranes, where the two molecules are closely physically opposed. In addition, these studies indicate that acid secretion is regulated by independent trafficking of KCNQ1 and H(+)-K(+)-ATPase.

The Golgi apparatus in the endomembrane-rich gastric parietal cells exist as functional stable mini-stacks dispersed throughout the cytoplasm.

BACKGROUND INFORMATION: Acid-secreting gastric parietal cells are polarized epithelial cells that harbour highly abundant and specialized, H+,K+ ATPase-containing, tubulovesicular membranes in the apical cytoplasm. The Golgi apparatus has been implicated in the biogenesis of the tubulovesicular membranes; however, an unanswered question is how a typical Golgi organization could regulate normal membrane transport within the membrane-dense cytoplasm of parietal cells. RESULTS: Here, we demonstrate that the Golgi apparatus of parietal cells is not the typical juxta-nuclear ribbon of stacks, but rather individual Golgi units are scattered throughout the cytoplasm. The Golgi membrane structures labelled with markers of both cis- and trans-Golgi membrane, indicating the presence of intact Golgi stacks. The parietal cell Golgi stacks were closely aligned with the microtubule network and were shown to participate in both anterograde and retrograde transport pathways. Dispersed Golgi stacks were also observed in parietal cells from H+,K+ ATPase-deficient mice that lack tubulovesicular membranes. CONCLUSIONS: These results indicate that the unusual organization of individual Golgi stacks dispersed throughout the cytoplasm of these terminally differentiated cells is likely to be a developmentally regulated event.

A critical role for the protein phosphatase 2A B'α regulatory subunit in dephosphorylation of sphingosine kinase 1.

Sphingosine kinase 1 (SK1) is an important regulator of cellular signalling that has gained recent attention as a potential target for anti-cancer therapies. SK1 activity, subcellular localization and oncogenic function are regulated by phosphorylation and dephosphorylation at Ser225. ERK1/2 have been identified as the protein kinases responsible for phosphorylation and activation of SK1. Conversely, dephosphorylation and deactivation of SK1 occurs by protein phosphatase 2A (PP2A). Active PP2A, however, is a heterotrimer, composed of tightly associated catalytic and structural subunits that can interact with an array of regulatory subunits, which are critical for determining holoenzyme substrate specificity and subcellular localization. Thus, PP2A represents a large family of holoenzyme complexes with different activities and diverse substrate specificities. To date the regulatory subunit essential for targeting PP2A to SK1 has remained undefined. Here, we demonstrate a critical role for the B'α (B56α/PR61α/PPP2R5A) regulatory subunit of PP2A in SK1 dephosphorylation. B'α was found to interact with the c-terminus of SK1, and reduce SK1 phosphorylation when overexpressed, while having no effect on upstream ERK1/2 activation. siRNA-mediated knockdown of B'α increased SK1 phosphorylation, activity and membrane localization of endogenous SK1. Furthermore, overexpression of B'α blocked agonist-induced translocation of SK1 to the plasma membrane and abrogated SK1-induced neoplastic transformation of NIH3T3 fibroblasts. Thus, the PP2A-B'α holoenzyme appears to function as an important endogenous regulator of SK1.

Isolation, culture and adenoviral transduction of parietal cells from mouse gastric mucosa.

Here we describe a method for the isolation of intact gastric glands from mice and primary culture and transfection of mouse gastric epithelial cells. Collagenase digestion of PBS-perfused mouse stomachs released large intact gastric glands that were plated on a basement membrane matrix. The heterogeneous gland cell cultures typically contain approximately 60% parietal cells. Isolated mouse parietal cells remain viable in culture for up to 5 days and react strongly with an antibody specific to the gastric H(+)/K(+) ATPase. Isolated intact mouse gastric glands and primary cultures of mouse parietal cells respond to the secretagogue, histamine. Typical morphological changes from a resting to an acid-secreting active parietal cell were observed. In resting cultures of mouse parietal cells, the H(+)/K(+) ATPase displayed a cytoplasmic punctate staining pattern consistent with tubulovesicle element structures. Following histamine stimulation, an expansion of internal apical vacuole structures was observed together with a pronounced redistribution of the H(+)/K(+) ATPase from the cytoplasm to the apical vacuoles. A reproducible procedure to express genes of interest exogenously in these cultures of mouse parietal cells was also established. This method combines recombinant adenoviral transduction with magnetic field-assisted transfection resulting in approximately 30% transduced parietal cells. Adenoviral-transduced parietal cells maintain their ability to undergo agonist-induced activation. This protocol will be useful for the isolation, culture and expression of genes in parietal cells from genetically modified mice and as such will be an invaluable tool for studying the complex exocytic and endocytic trafficking events of the H(+)/K(+) ATPase which underpin the regulation of acid secretion.

Two genetic loci independently confer susceptibility to autoimmune gastritis.

Autoimmune gastritis is a CD4+ T cell-mediated disease induced in genetically susceptible mice by thymectomy on the third day after birth. Previous linkage analysis indicated that Gasa1 and Gasa2, the major susceptibility loci for gastritis, are located on mouse chromosome 4. Here we verified these linkage data by showing that BALB.B6 congenic mice, in which the distal approximately 40 Mb of chromosome 4 was replaced by C57BL/6 DNA, were resistant to autoimmune gastritis. Analysis of further BALB.B6 congenic strains demonstrated that Gasa1 and Gasa2 can act independently to cause full expression of susceptibility to autoimmune disease. Gasa1 and Gasa2 are located between D4Mit352-D4Mit204 and D4Mit343-telomere, respectively. Numerical differences in Foxp3+ regulatory T cells were apparent between the BALB/c and congenic strains, but it is unlikely that this phenotype accounted for differences in autoimmune susceptibility. The positions of Gasa1 and Gasa2 correspond closely to the positions of Idd11 and Idd9, two autoimmune diabetes susceptibility loci in nonobese diabetic (NOD), mice and this prompted us to examine autoimmune gastritis in NOD mice. After neonatal thymectomy, NOD mice developed autoimmune gastritis, albeit at a slightly lower incidence and severity of disease than in BALB/c mice. Diabetes-resistant congenic NOD.B6 mice, harbouring a B6-derived interval encompassing the Gasa1/2-Idd9/11 loci, demonstrated a slight reduction in the incidence of autoimmune gastritis. This reduction was not significant compared with the reduction observed in BALB.B6 congenic mice, suggesting a difference in the genetic aetiology of autoimmune gastritis in NOD and BALB mice.

Characterization of a C57BL/6 congenic mouse strain of mucopolysaccharidosis type IIIA.

The original mucopolysaccharidosis type IIIA (MPS IIIA) mice were identified in a mixed background with contributions from four different strains. To ensure long-term stability and genetic homogeneity of this lysosomal storage disease (LSD) model, the aim of this study was to develop and characterize a C57BL/6 congenic strain. The B6.Cg-Sgsh(mps3a) strain compares favorably with the original mixed donor strain, exhibiting low liver sulfamidase activity and significant brain heparan sulfate-derived disaccharide elevation from birth. A rapid increase in brain disaccharide levels occurred after birth, with a plateau reached by 13 weeks of age at 110x the levels observed in brains of age-matched unaffected mice. Typical lysosomal inclusions were observed in cerebral cortical and cerebellar neurons and in liver hepatocytes and Kupffer cells. Ubiquitin-positive spheroids and GM(2)-ganglioside were also detected in brain. Using the Morris water maze in male mice, impaired memory and spatial learning was evident at 20 weeks of age in B6.Cg-Sgsh(mps3a) MPS IIIA mice. Other behavioral changes include motor, cognitive and sensory deficits, and aggression. Male B6.Cg-Sgsh(mps3a) MPS IIIA mice exhibited more behavioral abnormalities than B6.Cg-Sgsh(mps3a) MPS IIIA females, as observed previously in the original mixed background strain. Affected mice generally survive to 9 to 12 months of age, before death or euthanasia for humane reasons. Overall, minor differences were apparent between the new congenic and previously described mixed MPS IIIA strains. Availability of an in-bred strain will ensure more reproducible experimental outcomes thereby assisting in our goal of developing effective therapies for LSD with central nervous system disease.

Enzyme-replacement therapy from birth delays the development of behavior and learning problems in mucopolysaccharidosis type IIIA mice.

Mucopolysaccharidosis type IIIA (MPS IIIA; Sanfilippo syndrome) is a lysosomal storage disorder characterized by severe CNS degeneration, resulting in behavioral abnormalities and loss of learned abilities. Early treatment is vital to prevent long-term clinical pathology in lysosomal storage disorders. We have used naturally occurring MPS IIIA mice to assess the effects of long-term enzyme-replacement therapy initiated either at birth or at 6 wk of age. MPS IIIA and normal control mice received weekly i.v. injections of 1 mg/kg recombinant human sulfamidase until 20 wk of age. Sulfamidase is able to enter the brain until the blood-brain barrier completely closes at 10-14 d of age. MPS IIIA mice that were treated from birth demonstrated normal weight, behavioral characteristics, and ability to learn. MPS IIIA mice that were treated from birth performed significantly better in the Morris water maze than MPS IIIA mice that were treated from 6 wk of age or left untreated. A reduction in storage vacuoles in cells of the CNS in MPS IIIA mice that were treated from birth is consistent with the improvements observed. These data suggest that enzyme that enters the brain in the first few weeks of life, before the blood-brain barrier matures, is able to delay the development of behavior and learning difficulties in MPS IIIA mice.