¹Department of Genetics and Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, TN

^|[ast]|Supported in part by NIH grant DK 52025

Abstract

b-galactosidase (b-gal), a lysosomal enzyme involved in the removal of b-linked terminal galactosyl residues of many glycoconjugates, is deficient in the neurodegenerative lysosomal disorder G_M1-gangliosidosis (GM1). GM1-/-mice closely mimic the most fundamental aspects of the neuropathological and neurochemical abnormalities of the human disorder. Bone marrow progenitor cells have been used as a source of corrective protein because of their ability to repopulate the recipients and to supply functional enzyme to different cells by |[ldquo]|in trans|[rdquo]| correction. Hematopoietic progenitors transduced with a murine stem cell virus (MSCV)-based bicistronic retroviral vector over-expressing b-gal and the green fluorescent protein (GFP) marker were used for transplantation into sublethally irradiated GM1-/-mice. Transduction efficiency of total BM cells with the MSCV-b-gal ranged from 25|[ndash]|89% prior to the transplantation. b-gal expressing BM-derived cells were detected histologically and enzymatically in many tissues including spleen, liver, lungs, intestine and kidney after one, three and six months post transplantation (BMT). GFP-expressing cells of the erythroid, myeloid or lymphoid lineage were identified by FACS analysis of peripheral blood samples, collected at different time points after transplantation. Secondary transplantations demonstrated consistent long-term |[ldquo]|in vivo|[rdquo]| b-gal expression in all tissues including brain. In addition, the thin layer chromatography of brain lipids showed a reduction in the G_M1-ganglioside content in brainstem and cerebellum after three and six months post BMT. In line with the biochemical and histological findings, different behavioral tests including open field, rotorod and walking pattern, indicated a clear improvement of the neurological function in transplanted GM1-/-compared to untreated littermates. Taken together these results have encouraged the use of ex-vivo gene therapy for the treatment of GM1.