NEUROPATHOLOGY OF TWITCHER MICE - EXAMINATION BY HISTOCHEMISTRY, IMMUNOHISTOCHEMISTRY, LECTIN HISTOCHEMISTRY AND FOURIER-TRANSFORM INFRARED MICROSPECTROSCOPY

The twitcher mouse is an authentic animal model of globoid cell leukodystrophy, which is a genetic disease that affects the lysosomal enzyme galactocerebroside beta-galactosidase. This enzyme deficiency causes one of its substrates, galactosylsphingosine (psychosine), to accumulate in myelin-forming cells, which eventually results in their death. In the central nervous system, the death of oligodendrocytes is thought to cause a series of secondary pathological changes. In this study, several techniques were utilized to examine the neuropathology of two different brain regions in the twitcher mouse-the hindbrain and the cerebrum. Neuropathological changes were as follows: (1) demyelination was detected in the hindbrain but not in the cerebrum, (2) a high density of periodic acid-Schiff-positive cells were detected in the hindbrain and to a lesser extent in the cerebrum, (3) astrocyte gliosis was pronounced in both the hindbrain and cerebrum, and (4) macrophages were abundant in both the hindbrain and the cerebrum. We found that Periodic acid-Schiff-positive cells, astrocyte gliosis and macrophage infiltration were present in white and gray matter regions of the cerebrum, while they were generally absent from the granule and molecular layers of the cerebellum. In addition to these studies, we utilized the technique of Fourier transform infrared (FT-IR) microspectroscopy to identify the in situ distribution of psychosine in the brains of twitcher mice. Evidence was obtained that indicates a large accumulation of psychosine in the hindbrain, and to a lesser extent in the white matter of the cerebrum in the twitcher mouse, but not the normal mouse. There was no evidence for the accumulation of psychosine in the molecular layer of the cerebellum from the twitcher or normal mouse. Our conclusions are as follows: (1) pathology is more advanced in the hindbrain compared to the cerebrum, which is likely due to the hindbrain becoming myelinated prior to the cerebrum, (2) demyelination is not necessary for the development of secondary pathological changes, (3) pathology is not limited to white matter in the cerebrum, (4) pathology is not present in all brain regions, i.e. the granule and molecular layers of the cerebellum are devoid of pathological changes, and (5) psychosine accumulates in both the cerebrum and hindbrain, but not in the molecular layer of the cerebellum in the twitcher mouse. This study demonstrates that FT-IR microspectroscopy can be used to correlate chemical changes to histopathological changes in brains from twitcher mice, which suggests that FT-IR microspectroscopy may be a useful tool for studies examining other brain diseases.