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. 2021 Apr 29;15:673132. doi: 10.3389/fncel.2021.673132

Figure 1.

Figure 1

Cre-LoxP based systems to study Oligodendrocyte progenitor cell (OPC) functions. (A) Fluorescent proteins can be specifically expressed in OPCs in a Cre-LoxP system where Cre-recombinase or Cre-ERT2 (Cre fused to a mutant estrogen ligand-binding domain) is expressed downstream of an OPC-specific marker, such as NG2 or PDGFRα. Upon Tamoxifen administration (for Cre-ERT2), Cre-recombinase excises a floxed stop signal, which then permits expression of fluorescent protein under the ubiquitous Rosa26 promoter. Fluorescently-labeled OPCs will transmit the excised allele to their progeny. Lineage tracing of labeled-NG2-glia showed that OPCs give rise primarily to MBP+ve, MAG+ve, MOG+ve, PLP+ve oligodendrocytes, but could also generate GFAP+ve astrocytes or NeuN+ve neurons. (B) Diphtheria toxin receptor (DTR) can be specifically expressed in OPCs by the Cre-LoxP system described above. Cre-recombinase excises a floxed stop signal, which then permits expression of DTR under the ubiquitous Rosa26 promoter. Injection of diphtheria toxin (DT) then elicits apoptotic cell death in DTR-expressing cells. In a non-inducible system, such as the one depicted, DTR will be expressed in NG2+ cells and their progeny which (in the case of OPCs) will result in cell death of OPCs but also any derived progeny, including oligodendrocytes. Such models must be validated for specificity of expression of DTR in the desired cell type, such as via immunostaining for DTR and OPC-specific markers, or by quantifying loss of OPCs and other cell types following DT-administration.