The twitcher mouse: myelinogenesis in organotypic culture.

Myelinogenesis was followed in organotypic cultures of the spinal cord of the neurological mutant mouse, the Twitcher. As a clinically, pathologically and biochemically equivalent model of Krabbe disease this mutant is an important tool for investigating the nervous system. Normal initiation and development of myelination was observed. At 35 days in vitro (DIV) the Twitcher cultures exhibited blisters attached to the intact myelin sheath and bubbling of myelin suggestive of myelin breakdown. Myelin degeneration progressed thereafter. The Twitcher spinal cord survived in culture for more than two months, a period much longer than the life span of affected mice. In order to correlate pathological and biochemical changes, the activity of UDP-galactose:ceramide galactosyltransferase was quantitated in normal and Twitcher cultures. In both the Twitcher and the control groups the galactosyltransferase activity rapidly increased up to 20-25 DIV and then declined. The galactosyltransferase activity of the Twitcher tended to be lower than the controls even during the early myelination period. At 35 DIV the activity in the Twitcher was definitely lower than the controls, and at 52 DIV it was nearly negligible. The galactosyltransferase activity therefore correlated well with the morphologically observed early normal myelination and subsequent myelin degeneration.