Transcriptional regulation of scar gene expression in primary astrocytes.
The failure of the adult injured spinal cord to support axonal regeneration is in part attributed to the glial scar. Reactive astrocytes constitute a major cellular component of the glial scar and are heterogeneous with respect to the extracellular matrix proteins that they secrete. Astrocytes may produce antiregenerative molecules such as chondroitin sulphate proteoglycans (CSPGs) or proregenerative molecules such as laminin and fibronectin. While many different CSPGs are expressed after spinal cord injury (SCI) they all rely on the same enzymes, xylosyltransferase-I and -II (XT-I, XT-II) and chondroitin 4-sulfotransferase (C4ST) to add the repulsive chondroitin sulfate side chains to their core proteins. We show that XT-I, XT-II, and C4ST are part of a CSPG biosynthetic gene (CBG) battery. Using primary astrocyte cultures and quantitative PCR we demonstrate that TGFbeta2, PDGF, and IL-6 induce the expression of CBGs, laminin and fibronectin by several-fold. We further show that over-expression of the transcription factor SOX9 also strongly induces the expression of CBGs but does not increase the expression of laminin or fibronectin. Correspondingly, SOX9 knock-down in primary astrocytes causes a decrease in CBG and an increase in laminin and fibronectin mRNA levels. Finally, we show that the in vivo expression profiles of TGFbeta2, PDGF, IL-6, and SOX9 are consistent with their potential roles in differentially regulating CBGs, laminin and fibronectin gene expression in the injured spinal cord. This work suggests that SOX9 levels may be pivotal in determining the balance of pro- and anti-regenerative extracellular matrix molecules produced by astrocytes.
Gris
Paul
P
The Spinal Cord Injury Team, BioTherapeutics Research Group, Robarts Research Institute, London, Ontario, Canada.
Tighe
Allyson
A
Levin
David
D
Sharma
Rahul
R
Brown
Arthur
A
D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D002478:Cells, Cultured; D005260:Female; D005353:Fibronectins / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000502:physiology*; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006609:High Mobility Group Proteins / Q000494:pharmacology; D015151:Immunoblotting; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D015850:Interleukin-6 / Q000494:pharmacology; D007797:Laminin / Q000494:pharmacology; D009457:Neuroglia / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010430:Pentosyltransferases / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D012313:RNA / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055758:SOX9 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013119:Spinal Cord Injuries / Q000235:genetics / Q000378:metabolism; D015238:Sulfotransferases / Q000378:metabolism; D014157:Transcription Factors / Q000494:pharmacology; D053781:Transforming Growth Factor beta2 / Q000494:pharmacology; D000097608:UDP Xylose-Protein Xylosyltransferase
D005353:Fibronectins; D005904:Glial Fibrillary Acidic Protein; D006609:High Mobility Group Proteins; D015850:Interleukin-6; D007797:Laminin; D010430:Pentosyltransferases; D010982:Platelet-Derived Growth Factor; D012313:RNA; D055758:SOX9 Transcription Factor; D015238:Sulfotransferases; D014157:Transcription Factors; D053781:Transforming Growth Factor beta2; D000097608:UDP Xylose-Protein Xylosyltransferase; C019893:chondroitin 4-sulfotransferase