Notch1 and Numb genes are inversely expressed as oligodendrocytes differentiate.
The Notch1 pathway plays a fundamental role during the establishment of cell fates in the central nervous system (CNS) by regulating neural cell differentiation. In oligodendrocytes (OLs), Notch1 activity prevents these cells from becoming terminally mature, thereby influencing CNS myelination. Little is known of how OLs regulate the expression of this receptor at the gene level or if OLs have mechanisms to control the level of intracellular activity of the Notch1 pathway. In this study, we have found that Notch1 gene expression was higher in proliferative OL progenitor cells (OPCs) and was reduced when cells were forced to withdraw from the cell cycle and became mature, indicating that Notch1 gene expression is developmentally regulated in OLs. We observed that the blockade of terminal differentiation of OPCs by incubation with Delta1, an activator of Notch1, was a dominant process and OL-differentiating signals such as thyroid hormone could not overcome this inhibition in culture. This suggests that a downregulation of the Notch1 pathway might be required to allow OPCs to enter terminal differentiation. We also provide evidence that OPCs and OLs express the Numb gene, a known negative regulator of Notch1 activity. In vivo, Numb was found in postnatal OLs from cerebellar and cerebral white matter. In vitro, Numb expression showed to be inversely correlated to that of Notch1, with higher levels of Numb proteins in mature OLs, in association with myelin-like membranes.
Givogri
Maria I
MI
Laboratory for Gene Therapy of Neurodegenerative Disorders, San Raffaele Telethon Institute for Gene Therapy, Milano, Italy.
Schonmann
Vilma
V
Cole
Ruth
R
De Vellis
Jean
J
Bongarzone
Ernesto R
ER
D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology; D050760:Cyclin-Dependent Kinase Inhibitor p27; D003593:Cytoplasm / Q000502:physiology; D015536:Down-Regulation; D020868:Gene Silencing; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D008934:Mitogens / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D009836:Oligodendroglia / Q000166:cytology* / Q000378:metabolism; D051381:Rats; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D015398:Signal Transduction / Q000187:drug effects; D013234:Stem Cells / Q000502:physiology; D013347:Subcellular Fractions / Q000378:metabolism; D014157:Transcription Factors; D014284:Triiodothyronine / Q000494:pharmacology; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D015854:Up-Regulation
C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D008565:Membrane Proteins; D008934:Mitogens; D009419:Nerve Tissue Proteins; C497763:Notch1 protein, rat; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D014284:Triiodothyronine; D050760:Cyclin-Dependent Kinase Inhibitor p27