Sulfatides in prenatal metachromatic leukodystrophy

Imaging of complex sulfatides SM3 and SB1a in mouse kidney using MALDI-TOF/TOF mass spectrometry

Sulfatides, a class of acidic glycosphingolipids, are highly expressed in mammalian myelin and in kidney, where they are thought to stabilize neuronal structures and signaling and to influence osmotic stability of renal cells, respectively. Recently, 9-aminoacridine (9-AA) has been introduced as a negative ion matrix that displays high selectivity for low complexity galactosylceramid-I(3)-sulfate sulfatides and that is suitable for quantitative analysis by matrix-assisted desorption/ionization (MALDI) mass spectrometry (MS). Analyzing acidic fractions of lipid extracts and cryosections from kidneys of wild type and arylsulfatase A-deficient (ASA -/-) mice, we demonstrate that 9-AA also enables sensitive on-target analysis as well as imaging of complex lactosylceramide-II(3)-sulfate and gangliotetraosylceramide-II(3), IV(3) bis-sulfate sulfatides by MALDI-TOF/TOF MS. Utilizing the MALDI imaging MS technique, we show differential localization in mouse kidney of (1) sulfatides with identical ceramide anchors, but different glycan-sulfate head groups but also of (2) sulfatides with identical head groups but with different acyl- or sphingoid base moieties. A comparison of MALDI images of renal sulfatides from control and sulfatide storing arylsulfatase A-deficient (ASA -/-) mice revealed relative expression differences, very likely reflecting differences in sulfatide turnover of the various renal cell types. These results establish MALDI imaging MS with 9-AA matrix as a label-free method for spatially resolved ex vivo investigation of the relative turnover of sulfatides in animal models of human glycosphingolipid storage disease.

Gene therapy for lysosomal storage disorders

The lysosomal storage disorders (LSD) are monogenic inborn errors of metabolism with heterogeneous pathophysiology and clinical manifestations. In the last decades, these disorders have been models for the development of molecular and cellular therapies for inherited metabolic diseases. Studies in preclinical in vitro systems and animal models have allowed the successful development of bone marrow transplantation (BMT) and enzyme replacement therapy (ERT) as therapeutic options for several LSDs. However, BMT is limited by poor donor availability and high morbidity and mortality, and ERT is not a life-long cure. Moreover, the neuropathology present in many LSDs responded poorly, if at all, to these treatments. Therefore, gene therapy is an attractive therapeutic alternative. Gene therapy strategies for LSDs have employed ex vivo gene transduction of cellular targets with subsequent transplantation of the enzymatically corrected cells, or direct in vivo delivery of the viral vectors. Oncoretroviral vectors and more recently adeno associated vectors (AAV) and lentiviral vectors have been extensively tested, with some success. This review summarises the main gene therapy strategies which have been employed or are under development for both non-neurological and neuronopathic LSDs. Some of the in vitro and in vivo preclinical studies presented herein have provided the rationale for a gene therapy clinical trial for Gaucher disease Type I.

Gene transfer approaches to the lysosomal storage disorders

The work summarized in this paper used animal and cell culture models systems to develop gene therapy approaches for the lysosomal storage disorders. The results have provided the scientific basis for a clinical trial of gene transfer to hematopoietic stem cells (HSC) in Gaucher disease which is now in progress. The clinical experiment is providing evidence of HSC transduction, competitive engraftment of genetically corrected HSC, expression of the GC transgene, and the suggestion of a clinical response. In this paper we will review the progress made in Gaucher disease and include how gene transfer might be studied in other lysosomal storage disorders.

Membrane bilayer instability and the pathogenesis of disorders of myelin

We have previously shown that total lipid extracts from normal nervous tissues spontaneously form a structure in vitro resembling the cell membrane bilayer, but only at a critical temperature, T*, equal to the 'physiological' temperature of the original tissues. In the present study, we found T* for normal human myelin lipids was 37 degrees C, in agreement with the concept that lipid metabolic pools maintain a critical composition in vivo which permits spontaneous formation of the (myelin) membrane bilayer at normal body temperature. But T* for myelin lipids from a patient with metachromatic leukodystrophy was less than 30 degrees C. Thus, myelin lipid composition was inappropriate for normal bilayer stability at this patient's core temperature, suggesting a mechanism whereby defective lipid metabolism in this disease could produce pathological myelin. The shift in T* in this patient was unlikely to be simply secondary to myelin destruction, as myelin lipids from a patient with advanced multiple sclerosis yielded a normal value for T* of 37 degrees C, even when extracted from areas of extensive demyelination.