Constitutive expression of interleukin-1beta (IL-1beta) in rat oligodendrocytes

The RT-PCR analysis of RNA from progenitor and differentiated primary rat oligodendrocytes, and from the oligodendrocyte CG-4 cell line, shows the presence of the IL-1beta mRNA, the type I IL-1beta receptor and the IL-1 receptor accessory protein in these cells. In situ hybridization of a rat IL-1beta probe to primary progenitor and differentiated rat oligodendrocytes results in a positive signal. The double hybridization of the IL-1beta probe, together with an oligodendrocyte-specific differentiation marker, to sections of postnatal rat brain at different stages of differentiation is also positive. The double immuno-labelling technique utilized indicates coincidence of the signals on the brain slices. The results show that IL-1beta mRNA is constitutively expressed in rat brain oligodendrocytes from 1 day after birth onward. In agreement with this observation, CG-4 cells, primary progenitor and differentiated rat oligodendrocytes are positively stained by antibodies against IL-1beta. Postnatal brain slices from 1 and 4 day old and adult rats, labelled with a double immunofluorescence technique, are also stained by antibodies against IL-1beta. This signal coincides with that of antibodies against oligodendrocyte-specific surface markers. We conclude that IL-1beta is constitutively expressed in rat brain progenitor and differentiated oligodendrocytes.     

Galactosylceramidase deficiency causes sperm abnormalities in the mouse model of globoid cell leukodystrophy

The classical recessive mouse mutant, "the twitcher," is one of the several animal models of the human globoid cell leukodystrophy (Krabbe disease) caused by a deficiency in the gene encoding the lysosomal enzyme galactosylceramidase (GALC). The failure to hydrolyze galactosylceramide (gal-cer) and galactosylsphingosine (psychosine) leads to degeneration of oligodendrocytes and severe demyelination. Substrate for GALC is also the galactosyl-alkyl-acyl-glycerol (GalAAG), precursor of the seminolipid, the most abundant glycolipid in spermatozoa of mammals. In this paper, we report the pathobiology of the testis and sperm in the twitcher mouse and demonstrate the importance of GALC for normal sperm maturation and function. The GALC deficit results in accumulation of GalAAG in the testis of the twitcher mouse. Morphological studies revealed that affected spermatozoa have abnormally swollen acrosomes and angulation of the flagellum mainly at midpiece-principal piece junction. Multiple folding of the principal piece was also observed. Electron microscopy analysis showed that in the twitcher sperm, acrosomal membrane is redundant, detached from the nucleus and folded over. Disorganization and abnormal arrangements of the axoneme components were also detected. These results provide in vivo evidence that GALC plays a critical role in spermiogenesis.     

Activation of Cell Cycle Regulatory Proteins in the Apoptosis of Terminally Differentiated Oligodendrocytes

There is increasing evidence that proteins normally involved in the cell cycle play a role in the regulation of neuronal apoptotic death following various insults. However, it is not clear if the same mechanisms regulate cell death of oligodendrocytes as well. In this study, we investigated the mechanism of ceramide-induced apoptosis in primary rat oligodendrocytes. We show that ceramide treatment initiates a cascade of biochemical events involving cell cycle regulatory proteins. Although at the time of induction of cell death the oligodendrocytes are postmitotic, activation of c-myc and translocation of Cdc25A into the nucleus can be demonstrated. Of particular interest are the findings of the up-regulation of PCNA and down-regulation of p21WAF1/CIP1 protein, an inhibitor of cell-cycle progression. The current results show that activation of regulatory cell-cycle proteins at the oligodendrocytes G1-S checkpoint may constitute a crucial step of the death pathway of oligodendrocytes.     

Transduction of Cultured Oligodendrocytes from Normal and Twitcher Mice by a Retroviral Vector Containing Human Galactocerebrosidase (GALC) cDNA

Krabbe disease or globoid cell leukodystropy is a lysosomal disorder caused by a deficiency of galactocerebrosidase (GALC) activity. This results in defects in myelin that lead to severe symptoms and early death in most human patients and animals with this disease. With the cloning of the GALC gene and the availability of the mouse model, called twitcher, it was important to evaluate the effects of providing GALC via a retroviral vector to oligodendrocytes in culture. After differentiation, the untransduced cells from normal mice extended highly branched processes while those from the twitcher mice did not. oligodendrocytes in culture can be readily transduced to produce much higher than normal levels of GALC activity. Transduced normal and twitcher cells formed clusters when plated at high density. Transduction of twitcher oligodendrocytes plated at lower density, followed by differentiation, resulted in some cells having a completely normal appearance with highly branched processes. Other cells showed retraction and fragmentation. Perhaps over expression of GALC activity may be detrimental to oligodendrocytes. These studies demonstrate that the phenotype of twitcher oligodendrocytes can be corrected by providing GALC via gene transfer, and this could lead the way to future studies to treat this disease.