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Prolonged Sox4 expression in oligodendrocytes interferes with normal myelination in the central nervous system.

ABSTRACT: The highly related transcription factors Sox4 and Sox11 are both expressed in oligodendrocyte precursors. Yet whether they have a function in oligodendrocyte development is unknown. By overexpressing Sox4 under the control of 3.1 kb of 5' flanking sequences of the myelin basic protein gene in transgenic mice, we extended Sox4 expression in the oligodendrocyte lineage from oligodendrocyte precursors to cells undergoing terminal differentiation. As a consequence of transgene expression, mice develop the full spectrum of phenotypic traits associated with a severe hypomyelination during the first postnatal weeks. Myelin gene expression was severely reduced, and myelin dramatically thinned in several central nervous system (CNS) regions. Despite these disturbances in CNS myelination, the number of oligodendrocytic cells remained unaltered. Considering that apoptosis rates were normal and proliferation only slightly increased, oligodendrocytes likely persist in a premyelinating to early myelinating state. This shows that prolonged Sox4 expression in cells of the oligodendrocyte lineage is incompatible with the acquisition of a fully mature phenotype and argues that the presence of Sox4, and possibly Sox11, in oligodendrocyte precursors may normally prevent premature differentiation.

SUBMITTER: Potzner MR

PROVIDER: S-EPMC1952099 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Multiple sclerosis (MS) is a demyelinating disease of the central nervous system that presents with variable pathologies that may reflect different disease-causing mechanisms. Existing animal models of MS induce pathology using either local injection of gliotoxins or stimulation of the immune system with myelin-related peptides. In none of these models is the primary cellular target well characterized, and although demyelination is a hallmark pathological feature in MS, it is unclear to what extent this reflects local oligodendrocyte loss. To unambiguously identify the effects of oligodendrocyte death in the absence of inflammatory stimulation, we developed a method for experimentally inducing programmed cell death selectively in mature oligodendrocytes and assessed the effects on demyelination, immunological stimulation, and gliosis. The resulting pathology is discussed relative to observed MS pathologies.Oligodendrocyte apoptosis was induced in the adult rat brain using a lentivirus to express experimentally inducible caspase 9 (iCP9) cDNA under transcriptional control of the promoter for myelin basic protein, which is oligodendrocyte-specific. Activation of iCP9 was achieved by distal injection of a small molecule dimerizer into the lateral ventricle resulting in localized, acute oligodendrocyte apoptosis.Induced oligodendrocyte apoptosis resulted in rapid demyelination and robust, localized microglial activation in the absence of peripheral immune cell infiltration. Lesion borders showed layers of preserved and degraded myelin, whereas lesion cores were demyelinated but only partially cleared of myelin debris. This resulted in local proliferation and mobilization of the oligodendrocyte progenitor pool.This approach provides a novel model to understand the pathological changes that follow from localized apoptosis of myelinating oligodendrocytes. It provides the first direct proof that initiation of apoptosis in oligodendrocytes is sufficient to cause rapid demyelination, gliosis, and a microglial response that result in lesions sharing some pathological characteristics with a subset of MS lesions.

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Prolonged Sox4 expression in oligodendrocytes interferes with normal myelination in the central nervous system.

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