Sulfatide is a galactolipid and a major lipid component of the myelin sheath. Its production is catalyzed by the enzyme cerebroside sulfotransferase (CST). To determine the functions of sulfatide, the gene encoding CST was genetically disrupted resulting in mice incapable of sulfatide synthesis. Using these mice, it has been shown in the central nervous system (CNS) that sulfatide is essential for normal myelin synthesis and stability even though the onset of myelination is not impaired. Additionally, proper initial clustering of paranodal proteins and cluster maintenance of nodal proteins is impaired suggesting that paranodal domains are important for long-term node stability. In contrast to the CNS, a requirement for sulfatide in the initiation of myelination, and in initiation of paranodal and nodal clustering or in the long-term maintenance of these clusters in the peripheral nervous system (PNS) has not been analyzed. Therefore, we have employed a combination of electron microscopic, immunocytochemical, and confocal microscopic analyses of the CST KO mice to determine the role of sulfatide in PNS myelination and onset of protein domain formation and maintenance. For these studies we have quantified myelin thickness, paranodal structural integrity, and the number of paranodal and nodal protein clusters in the CST KO and wild type mice at 4 days, 7 days, and 10 months of age. Our findings indicate that myelination onset is not delayed in the absence of sulfatide and that both the node and paranode are grossly normal; however, closer analysis reveals that paranodal junctions are compromised, Schwann cell microvilli are disoriented and the myelin-axon interface along the internodal region is transiently disrupted. In addition, we report that the paranodal myelin protein neurofascin 155 (Nfasc155) shows a transient decrease in initial clustering in the CST null mice at 4 days of age that is restored to WT levels by 7 days of age that is also maintained in the adult mice. Whereas nodal clustering of neuronal voltage-gated sodium channels is initially normal, cluster number is significantly but also transiently reduced by 7 days of age. By 10 months of age, the number of sodium channel clusters is restored to normal levels. In contrast, clustering of neither the paranodal neuronal protein contactin nor the myelin nodal protein gliomedin is altered at any of the ages studied. Together our findings suggest that sulfatide is not essential for PNS myelination or for protein domain formation in contrast to its more vital role in the development and maintenance of the CNS.
| Identifer | oai:union.ndltd.org:vcu.edu/oai:scholarscompass.vcu.edu:etd-1327 |
| Date | 23 April 2012 |
| Creators | Herman, Heather |
| Publisher | VCU Scholars Compass |
| Source Sets | Virginia Commonwealth University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | © The Author |
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