SoxD Proteins Influence Multiple Stages of Oligodendrocyte Development and Modulate SoxE Protein Function

SummaryThe myelin-forming oligodendrocytes are an excellent model to study transcriptional regulation of specification events, lineage progression, and terminal differentiation in the central nervous system. Here, we show that the group D Sox transcription factors Sox5 and Sox6 jointly and cell-autonomously regulate several stages of oligodendrocyte development in the mouse spinal cord. They repress specification and terminal differentiation and influence migration patterns. As a consequence, oligodendrocyte precursors and terminally differentiating oligodendrocytes appear precociously in spinal cords deficient for both Sox proteins. Sox5 and Sox6 have opposite functions than the group E Sox proteins Sox9 and Sox10, which promote oligodendrocyte specification and terminal differentiation. Both genetic as well as molecular evidence suggests that Sox5 and Sox6 directly interfere with the function of group E Sox proteins. Our studies reveal a complex regulatory network between different groups of Sox proteins that is essential for proper progression of oligodendrocyte development

Transcription factor Zfp276 drives oligodendroglial differentiation and myelination by switching off the progenitor cell program

In oligodendrocytes of the vertebrate central nervous system a complex network of transcriptional regulators is required to ensure correct and timely myelination of neuronal axons. Here we identify Zfp276, the only mammalian ZAD-domain containing zinc finger protein, as a transcriptional regulator of oligodendrocyte differentiation and central myelination downstream of Sox10. In the central nervous system, Zfp276 is exclusively expressed in mature oligodendrocytes. Oligodendroglial deletion of Zfp276 led to strongly reduced expression of myelin genes in the early postnatal mouse spinal cord. Retroviral overexpression of Zfp276 in cultured oligodendrocyte precursor cells induced precocious expression of maturation markers and myelin genes, further supporting its role in oligodendroglial differentiation. On the molecular level, Zfp276 directly binds to and represses Sox10-dependent gene regulatory regions of immaturity factors and functionally interacts with the transcriptional repressor Zeb2 to enable fast transition of oligodendrocytes to the myelinating stage

Sox9 overexpression exerts multiple stage‐dependent effects on mouse spinal cord development

Abstract The high‐mobility‐group (HMG)‐domain protein Sox9 is one of few transcription factors implicated in gliogenesis in the vertebrate central nervous system. To further study the role of Sox9 in early spinal cord development, we generated a mouse that allows expression of Sox9 in a temporally and spatially controlled manner. Using this mouse, we show that premature Sox9 expression in neural precursor cells disrupted the neuroepithelium of the ventricular zone. Sox9 also compromised development and survival of neuronal precursors and neurons. Additionally, we observed in these mice substantial increases in oligodendroglial and astroglial cells. Reversing the normal order of appearance of essential transcriptional regulators during oligodendrogenesis, Sox10 preceded Olig2. Our study reinforces the notion that Sox9 has a strong gliogenic activity. It also argues that Sox9 expression has to be tightly controlled to prevent negative effects on early spinal cord structure and neuronal development

Ep400 deficiency in Schwann cells causes persistent expression of early developmental regulators and peripheral neuropathy

Schwann cells ensure efficient nerve impulse conduction in the peripheral nervous system. Their development is accompanied by defined chromatin changes, including variant histone deposition and redistribution. To study the importance of variant histones for Schwann cell development, we altered their genomic distribution by conditionally deleting Ep400, the central subunit of the Tip60/Ep400 complex. Ep400 absence causes peripheral neuropathy in mice, characterized by terminal differentiation defects in myelinating and non-myelinating Schwann cells and immune cell activation. Variant histone H2A.Z is differently distributed throughout the genome and remains at promoters of Tfap2a, Pax3 and other transcriptional regulator genes with transient function at earlier developmental stages. Tfap2a deletion in Ep400-deficient Schwann cells causes a partial rescue arguing that continued expression of early regulators mediates the phenotypic defects. Our results show that proper genomic distribution of variant histones is essential for Schwann cell differentiation, and assign importance to Ep400-containing chromatin remodelers in the process

Elevated In Vivo Levels of a Single Transcription Factor Directly Convert Satellite Glia into Oligodendrocyte-like Cells

International audienceOligodendrocytes are the myelinating glia of the central nervous system and ensure rapid saltatory conduction. Shortage or loss of these cells leads to severe malfunctions as observed in human leukodystrophies and multiple sclerosis, and their replenishment by reprogramming or cell conversion strategies is an important research aim. Using a transgenic approach we increased levels of the transcription factor Sox10 throughout the mouse embryo and thereby prompted Fabp7-positive glial cells in dorsal root ganglia of the peripheral nervous system to convert into cells with oligodendrocyte characteristics including myelin gene expression. These rarely studied and poorly characterized satellite glia did not go through a classic oligodendrocyte precursor cell stage. Instead, Sox10 directly induced key elements of the regulatory network of differentiating oligodendrocytes, including Olig2, Olig1, Nkx2.2 and Myrf. An upstream enhancer mediated the direct induction of the Olig2 gene. Unlike Sox10, Olig2 was not capable of generating oligodendrocyte-like cells in dor-sal root ganglia. Our findings provide proof-of-concept that Sox10 can convert conducive cells into oligodendrocyte-like cells in vivo and delineates options for future therapeutic strategies

Olig2 overexpression does not generate oligodendrocyte-like cells in DRG.

<p><b>(A)</b> Spinal cord (SC), DRG and peripheral nerves (N) are schematically shown at E18.5. <b>(B-I)</b> IHC and ISH were carried out on transverse sections (thoracic level) of wildtype (Wt) and 2TetOlig2 embryos at E18.5 with antibodies directed against Olig2 (B, F) and riboprobes against <i>Mbp</i> (C, G), <i>Plp1</i> (D, H) and <i>Myrf</i> (E, I) and. Pictures were taken from the boxed DRG area. Size bars: 50 μm in B (valid for B-I).</p

Oligodendrocyte-like cells in DRG do not arise from boundary cap cells, Schwann cells or peripheral neurons.

<p>IHC was carried out with antibodies against GFP (A-D) or Olig2 (E-H) at E13.5 and E18.5 on transverse sections of embryos in which two copies of the <i>TetSox10</i> transgene were activated by <i>Krox20</i>::<i>Cre</i> (A, E), <i>Brn4</i>::<i>Cre</i> (B, C, F, G), or <i>Dhh</i>::<i>Cre</i> (D, H) instead of <i>Sox10</i>::<i>Cre</i>. Contours of spinal cord and DRG are marked by stippled lines. Boundary cap cells are marked by arrows in A, Schwann cells by arrowheads in D. Size bar in A, valid for A-H: 50 μm.</p

Sox10 overexpression in DRG leads to appearance of oligodendrocyte-like cells.

<p><b>(A)</b> Spinal cord (SC), DRG and peripheral nerves (N) are schematically shown at E18.5. Areas shown in C-E and G-U are marked as blue and yellow squares. <b>(B-U)</b> ISH and IHC were carried out on transverse sections (thoracic level) of wildtype (Wt) and 2TetSox10 embryos at E18.5 with riboprobes against <i>Plp1</i> (B, C, F, G), <i>Mbp</i> (D, H) and <i>Myrf</i> (E, I) or antibodies directed against Olig2 (J, P), Olig1 (K, Q), Nkx2.2 (L, R), Sox9 (M, S), Oct6 (N, T) and Krox20 (O, U). The areas from which pictures were taken are indicated by the blue or yellow color in the box above the panels. Color coding is according to the scheme in A. Stippled lines in N, O, T, U correspond to the nerve-DRG boundary. <b>(V-Y)</b> Dissociated cells from DRG of E14.5-old wildtype (V) and 2TetSox10 (W-Y) mouse embryos were co-cultured with rat DRG neurons for 4 weeks under myelinating conditions before immunocytochemical staining with Nf165 (red) and Mbp (green in V, W, Y and white in X). Nuclei were counterstained in Y with 4,6-diamidino-2-phenylindole (Dapi) (blue). W, X, Y show an example of a myelinating oligodendrocyte photographed with a Leica DMI6000 B inverted microscope equipped with a DFC350 FX camera (V, W) or a Zeiss LSM 780 confocal microscope (X, Y). Size bars: 50 μm in B (valid for B, F), C (valid for C-E, G-U) and V (valid for V, W); 20 μm in X (valid for X, Y).</p

OLE is a Sox10-dependent oligodendroglial enhancer in vivo.

<p><b>(A-H)</b> The expression pattern of the lacZ reporter was followed during embryonic and early postnatal development in the spinal cord of <i>OLE-lacZ</i> (A-D) and <i>OLEa-lacZ</i> (E-H) transgenic animals by X-gal staining of transverse thoracic sections at E13.5, E15.5, E18.5 and P3. Size bar in A, valid for A-H: 200 μm. <b>(I-P)</b> Co-IHC was performed on spinal cord tissue of perinatal <i>OLE-lacZ</i> (I, J, M, N) and <i>OLEa-lacZ</i> (K, L, O, P) transgenic animals using antibodies directed against ß-galactosidase (in green) in combination with antibodies directed against Olig2 (I, K), Mbp (J, L), NeuN (M, O) and GFAP (N, P) (all in red). Pictures were taken from the ventral mantle zone for M, O and from the ventral marginal zone for all other panels. Size bar in I, valid for I-P: 20 μm. <b>(Q-T”)</b> Additionally, co-IHC was performed on DRG of mice that carried the <i>OLE-lacZ</i> (Q-R”) or the <i>OLEa-lacZ</i> (S-T”) transgene on a wildtype (Control) or 2TetSox10 background using antibodies directed against ß-galactosidase (green) in combination with antibodies directed against Olig2 (red). Nuclei were counterstained with Dapi (blue). Shown are single fluorescences for ß-galactosidase (Q-T) and Olig2 (Q’-T’) and the merge (Q”-T”) for each IHC. Size bar in Q, valid for Q-T”: 50 μm.</p