Pathogenesis of axonal dystrophy and demyelination in alphaA-crystallin-expressing transgenic mice

Abstract

We recently described a transgenic mouse strain overexpressing hamster alphaA-crystallin, a small heat shock protein, under direction of the hamster vimentin promoter. As a result myelin was degraded and axonal dystrophy in both central nervous system (especially spinal cord) and peripheral nervous system occurred. Homozygous transgenic mice developed hind limb paralysis after 8 weeks of age and displayed progressive loss of myelin and axonal dystrophy in both the central and peripheral nervous system with ongoing age. Pathologically the phenotype resembled, to a certain extent, neuroaxonal dystrophy. The biochemical findings presented in this paper (activity of the enzymes superoxide dismutase, catalase and transglutamase, myelin protein zero expression levels and blood sugar levels) confirm this pathology and exclude other putative pathologies like Amyothrophic Lateral Sclerosis and Hereditary Motor and Sensory Neuropathy. Consequently, an excessive cytoplasmic accumulation of the transgenic protein or a disturbance of the normal metabolism are considered to cause the observed neuropathology. Therefore, extra-ocular alphaA-crystallin-expressing transgenic mice may serve as a useful animal model to study neuroaxonal dystrophy.

Figure 1

Detection of the transgene pVim-αA (green label) on chromosome 1 (red label) by fluorescence in situ hybridization. Panel (a) Probe pVim-αA was hybridized to a metaphase spread of chromosomes derived from bone marrow cells. Panel (b) Partial karyotype; localization of the transgene to chromosome 1. The integration site was determined at position G3-H2, as indicated.

Figure 2

Western blots after SDS-PAGE of peripheral nerve proteins stained with a monoclonal antibody directed against P0 (a) and a polyclonal antibody directed against αA-crystallin (b). Lane (1) prestained marker (NOVEX); lane (2) transgenic mouse F13 48 male; lane (3) transgenic mouse F13 60 female; lane (4) control mousse F13 78 male and lane (5) control mouse F13 81 female.

Figure 3

Basic urea-polyacrylamide gel electrophoresis of spinal cord extract. Except for lane 1 A SOD activity was detected by disappearance of blue staining. Lane (1) bovine α-crystallin, containing the non-phosphorylated (αA and αB) and mono-phosphorylated α-crystallins (αAp and αBp): lane 1A stained with amido black, showing the positions of the α-crystallin subunits on a urea-gel run in parallel; lane (1B) bovine α-crystallin corresponding to lane 1 A; lane (2) transgenic mouse F7 1 female; lane (3) control mouse F7 2 female; lane (4) control mouse F7 3 female; lane (5) transgenic mouse F7 17 male; lane (6) transgenic mouse F7 18 male; lane (7) transgenic mouse F7 98 male; lane (8) transgenic mouse F7 99 male. X = blank.

Figure 4

(a) Transgenic mouse showing hind limb paralysis at 8 weeks of age. (b) Control mouse.