Over-expression of human lysosomal alpha-mannosidase in mouse embryonic stem cells

Global Proteome Profiling of a Marine Copepod and the Mitigating Effect of Ocean Acidification on Mercury Toxicity after Multigenerational Exposure

Previously, we found that ocean acidification (OA) mitigates mercury (Hg) toxicity to marine copepod Tigriopus japonicus under multigenerational exposure (four generations, F0-F3). To determine the response mechanisms of T. japonicus against long-term exposure to OA and Hg pollution, we investigated the proteome of F3 copepods after multigenerational exposure to four conditions: pCO₂ 400 μatm + control; pCO₂ 1000 μatm + control; pCO₂ 400 μatm +1.0 μg/L Hg; and pCO₂ 1000 μatm +1.0 μg/L Hg. Functional enrichment analysis indicated that OA enhanced the copepod's energy production mainly by increasing protein assimilation and proteolysis as a compensatory strategy, which explained its physiological resilience to reduced pH. Conversely, Hg treatment decreased many critical processes, including ferric iron binding, antioxidant activity, cellular homeostasis, and glutathione metabolism, and these toxic events could translate into higher-level responses, i.e., restrained reproduction in copepods. Importantly, the mediation of Hg toxicity in T. japonicus by OA could be explained by the enhanced lysosome-autophagy pathway proteomes that are responsible for repairing and removing damaged proteins and enzymes under stress. Overall, this study provided molecular insights into the response of T. japonicus to long-term exposure of OA and Hg, with a particular emphasis on the mitigating impact of the CO₂-driven acidification on Hg toxicity.

Embryonic stem cell-derived glial precursors as a vehicle for sulfamidase production in the MPS-IIIA mouse brain

Pluripotent stem cells, including human embryonic stem cells and induced pluripotent stem cells, have generated much excitement about their prospects for use in cell transplantation therapies. This is largely attributable to their virtually unlimited growth potential, their ability to be precisely genetically altered in culture, and their utility for forming differentiated cell populations with potential clinical applications. Lysosomal storage diseases such as Sanfilippo syndrome (MPS-IIIA) represent ideal candidate diseases for the evaluation of cell therapies in the central nervous system (CNS). These diseases exhibit widespread pathology yet result from a single gene deficiency, in the case of Sanfilippo syndrome the lysosomal enzyme sulfamidase. The aim of this study was to investigate mouse embryonic stem (ES) cell-derived glial precursor cells as a vehicle for sulfamidase delivery in the MPS-IIIA mouse brain. In this study we have created a mouse ES cell line genetically modified to stably express and secrete high levels of human sulfamidase and a protocol for the in vitro derivation of large numbers glial precursors from ES cells. Differentiation of sulfamidase-expressing ES cells resulted in cell populations with sustained secretion of high levels of sulfamidase, comprised primarily of glial precursor cells with minor contaminants of other neural cell phenotypes but not residual pluripotent cells. CNS implantation studies demonstrated that ES cell-derived glial precursor cells formed using this differentiation method were able to engraft and survive for at least 12 weeks following implantation. The percentage of engraftment was quantified in different regions of the brain in 2-, 4-, and 8-week-old normal and MPS-IIIA mice. No teratomas were observed in any of the cell-transplanted animals. The results of this study support the further investigation of sulfamidase-expressing glial precursor cells as a vehicle for delivery of deficient enzyme into the CNS of MPS-IIIA mice.

GAL4-NF-kappaB fusion protein augments transgene expression from neuronal promoters in the rat brain

Targeted gene expression mediated by a mammalian cellular promoter is desirable for gene therapy in the brain, where there are a variety of different neuronal phenotypes, several types of supportive cells, and blood vessels. However, this approach can be hampered by weak activity of some cellular promoters. In view of the potency of the transcription factor NF-kappaB in regulating neuronal gene expression, we have assessed whether it can be used to enhance the strength of neuron-specific promoters. Our approach was to use a neuronal promoter to drive expression of a chimeric transactivator, which consisted of a part of the transcriptional activation domain of the NF-kappaB p65 protein fused to the DNA-binding domain of GAL4 protein from yeast. The second copy of the neuronal promoter was modified by introducing the unique GAL4 binding sequences at its 5' end and used to drive the expression of a transgene. Binding of the chimeric transcriptional activator upstream of the second promoter was expected to potentiate its transcriptional activity. In this study, the approach was applied to the platelet-derived growth factor beta chain and synapsin-1 neuron-specific promoters and tested in vitro and in vivo using plasmid, lentiviral, and baculoviral vectors. We observed up to a 100-fold improvement in reporter gene expression in cultured neurons and 20-fold improvement in the rat brain in vivo. Moreover, the cell-type specificity of the two tested promoters was well preserved and restricted to neurons. Finally, the expression driven by the new lentiviral vectors with the p65-potentiated synapsin-1 promoter showed no signs of decline or cell damage 4 weeks after injection. This approach should be suitable for constructing powerful and stable gene expression systems based on weak cell-specific promoters in neuronal phenotypes.

Embryonic stem cell-based reduction of central nervous system sulfatide storage in an animal model of metachromatic leukodystrophy

Pluripotency, virtually unlimited self-renewal and amenability to genetic modification make embryonic stem (ES) cells an attractive donor source for cell-mediated gene therapy. In this proof of concept study, we explore whether glial precursors derived from murine ES cells (ESGPs) and engineered to overexpress human arylsulfatase A (hASA) can cross-correct the metabolic defect in an animal model of metachromatic leukodystrophy (MLD). Transfected ES cells showed an up to 30-fold increase in ASA activity. Following in vitro differentiation, high expression of ASA was found in all stages of neural and glial differentiation. hASA-overexpressing ESGPs maintained their ability to differentiate into astrocytes and oligodendrocytes in vitro and in vivo. After transplantation into the brain of neonatal ASA-deficient mice, hASA-overexpressing ESGPs were found to incorporate into a variety of host brain regions. Four weeks after engraftment, immunofluorescence analyses with an antibody to sulfatide revealed a 46.7+/-4.0% reduction of immunoreactive sulfatide deposits in the vicinity of the hASA-positive engrafted cells, thereby significantly extending the rate of sulfatide reduction achieved by the endogenous ASA activity of non-hASA-transfected control cells (21.1+/-5.8%). These findings provide first in vivo evidence that ES cells may serve as a potential donor source for cell-mediated enzyme delivery in storage disorders such as MLD.