The twitcher mouse is a murine model of human globoid cell leukodystrophy (GLD; Krabbe disease) caused by a genetic defect in the activity of galactosylceramidase (GALC). An accumulation of cytotoxic metabolite, galactosylsphingosine (psychosine), in myelin forming cells (oligodendrocytes and Schwann cells) of the twitcher mouse as well as patients with GLD has been suggested to cause dysfunction of these cells and subsequent demyelination in the central and peripheral nervous system. To investigate further the cellular pathomechanism of GLD, we established spontaneously immortalized Schwann cell lines from the twitcher mouse. Long-term cultures of Schwann cells derived from dorsal root ganglia and consecutive peripheral nerves of 3-week-old twitcher mice were maintained for 6 months, and spontaneously developed colonies were expanded further and characterized. One of the cell lines, designated TwS1, showed distinct Schwann cell phenotypes, was passaged twice a week and maintained for over 10 months without phenotypic alterations. The TwS1 cells had a nonsense mutation in the GALC genome, and showed markedly reduced GALC activity and elevated psychosine levels. Ultrastructurally, varieties of cytoplasmic inclusions were demonstrated in TwS1 cells. When TwS1 cells were infected with a retrovirus vector encoding GALC, GALC activity was markedly increased and psychosine levels were significantly decreased. These immortalized Schwann cells can be useful in studies on the nervous system lesions in GLD.