Murine spinal cord transcriptome analysis following reduction of prevalent myelin cDNA sequences

Myelin Sheath Injury in Kaolin-Induced Hydrocephalus: A Light and Electron Microscopy Study

BACKGROUND

In hydrocephalus, the impairment of cognitive and motor functions is thought to be partly due to injury to the myelin sheath of axons in the central nervous system. The exact nature of this injury is not completely understood.

METHODS

We induced hydrocephalus in 3-week-old rats with an intracisternal injection of kaolin suspension (0.04 ml of 200 mg/ml) and examined paraffin and ultrathin sections of the subcortical white matter from coronal slices of the cerebrum obtained at the level of the optic chiasm after sacrifice at weekly intervals for 4 weeks.

RESULTS

Over time, there was a progression of injury to the myelin sheath consisting of attenuation, lamella separation and accumulation of myelin debris, focal degeneration, and the appearance of casts and loops.

CONCLUSION

The results suggest that myelin injury in kaolin-induced hydrocephalus progresses with the duration and severity of ventriculomegaly.

Transcriptional analysis of glial cell differentiation in the postnatal murine spinal cord

Postnatal murine spinal cord represents a good model system to study mammalian central nervous system myelination in vivo as a basis for further studies in demyelinating diseases. Transcriptional changes were analyzed in SJL/J mice on postnatal day 0, 14, 49 and 231 (P0, P14, P49, P231) employing Affymetrix GeneChip Mouse Genome 430 2.0 Arrays. Additionally, marker gene signatures for astrocyte and oligodendrocyte lineage-stages were defined to study their gene expression in more detail. In addition, immunohistochemistry was used to quantify the abundance of commonly used glial cell markers. 6092 differentially regulated genes (DEGs) were identified. The up-regulated DEGs at P14, P49 and P231 compared to P0 exhibited significantly enriched associations to gene ontology terms such as myelination and lipid metabolic transport and down-regulated DEGs to neurogenesis and axonogenesis. Expression values of marker gene signatures for neural stem cells, oligodendrocyte precursor cells, and developing astrocytes were constantly decreasing, whereas myelinating oligodendrocyte and mature astrocyte markers showed a steady increase. Molecular findings were substantiated by immunohistochemical observations. The transcriptional changes observed are an important reference for future analysis of degenerative and inflammatory conditions in the spinal cord.