In Dr. Nolta’s lab, we are developing novel immune deficient mouse models for use in human stem cell research. The goal of our project is to verify human Mesenchymal Stem Cells (hMSCs) transduced with a lentiviral plasmid containing a working copy of N-Sulfoglucosamine Sulfohydrolase (SGSH) cDNA (hMSC-SGSH) as a therapeutic for direct application and amelioration of Sanfilippo in a novel immune deficient disease mouse model. Sanfilippo Syndrome, is an autosomal recessive neurodegenerative lysosomal storage disorder which currently has no cure or effective treatment. This fatal disorder results from a genetic defect at the SGSH locus of chromosome 17 leading to absence of Sulfamidase enzymatic activity in the lysosomes of affected cells and subsequent buildup of highly sulfated heparan sulfate in the CNS. Current management strategies for lysosomal storage disorders include enzyme replacement therapy (ERT) through recombinant enzyme injection. However, due to the blood-brain barrier this therapeutic remains unsuccessful in ameliorating disorders affecting the CNS. As a result, no treatment is available for Sanfilippo. In order to determine efficacy of hMSCs for ERT in the CNS we will be utilizing an in vivo disease model. However, one of the main difficulties in translational disease modeling in vivo is the production of an accurate disease model which allows for xenotransplantation of human cell-based therapeutics. Thus, for my project we will; (1) characterize neurological, morphological and behavioral disease phenotypes present in a B6.Cg-Sgshmps3a/PstJ mouse strain containing a spontaneous mutation at the SGSH locus; (2) produce a novel immune deficient Sanfilippo mouse model displaying these phenotypes through a 4 generation backcross of B6.Cg-Sgshmps3a/PstJ with B6.129S-Rag2tm1Fwa Cd47tm1Fpl Il2rgtm1Wjl/ mice containing targeted mutations in interleukin 2 receptor gamma chain (IL2rg) and recombination activating gene (Rag2); and (3) generate cultures of hMSCs transduced with our lentiviral SGSH construct (SGSH-hMSCs) which demonstrate elevated SGSH enzyme activity for further xenotransplantation in the CNS of our mouse model to test the hypothesis that these cells will cross-correct Sulfamidase deficient cells and lead to clearance of heparin sulfate from the CNS. The novel mouse model and our ongoing studies could lead to a potential therapeutic for Sanfilippo disease.