title: Transforming growth factor-beta1 regulates fibronectin isoform expression and splicing factor SRp40 expression during ATDC5 chondrogenic maturation.
abstract: Fibronectin (FN) isoform expression is altered during chondrocyte commitment and maturation, with cartilage favoring expression of FN isoforms that includes the type II repeat extra domain B (EDB) but excludes extra domain A (EDA). We and others have hypothesized that the regulated splicing of FN mRNAs is necessary for the progression of chondrogenesis. To test this, we treated the pre-chondrogenic cell line ATDC5 with transforming growth factor-beta1, which has been shown to modulate expression of the EDA and EDB exons, as well as the late markers of chondrocyte maturation; it also slightly accelerates the early acquisition of a sulfated proteoglycan matrix without affecting cell proliferation. When chondrocytes are treated with TGF-beta1, the EDA exon is preferentially excluded at all times whereas the EDB exon is relatively depleted at early times. This regulated alternative splicing of FN correlates with the regulation of alternative splicing of SRp40, a splicing factor facilitating inclusion of the EDA exon. To determine if overexpression of the SRp40 isoforms altered FN and FN EDA organization, cDNAs encoding these isoforms were overexpressed in ATDC5 cells. Overexpression of the long-form of SRp40 yielded an FN organization similar to TGF-beta1 treatment; whereas overexpression of the short form of SRp40 (which facilitates EDA inclusion) increased formation of long-thick FN fibrils. Therefore, we conclude that the effects of TGF-beta1 on FN splicing during chondrogenesis may be largely dependent on its effect on SRp40 isoform expression.
authors: Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors: Fei
authors: F
authors: Han
authors: James R
authors: JR
authors: Gilbert
authors: Gerald
authors: G
authors: Harrison
authors: Christopher S
authors: CS
authors: Adams
authors: Theresa
authors: T
authors: Freeman
authors: Zhuliang
authors: Z
authors: Tao
authors: Raihana
authors: R
authors: Zaka
authors: Hongyan
authors: H
authors: Liang
authors: Charlene
authors: C
authors: Williams
authors: Rocky S
authors: RS
authors: Tuan
authors: Pamela A
authors: PA
authors: Norton
authors: Noreen J
authors: NJ
authors: Hickok
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation; D019902:Chondrocytes / Q000378:metabolism* / Q000648:ultrastructure; D005353:Fibronectins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008855:Microscopy, Electron, Scanning; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D000068103:Serine-Arginine Splicing Factors; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology / Q000502:physiology*
chemical_list: D005353:Fibronectins; D009687:Nuclear Proteins; D020033:Protein Isoforms; D016601:RNA-Binding Proteins; D053773:Transforming Growth Factor beta1; D000068103:Serine-Arginine Splicing Factors