QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online 5 January 2005
doi: 10.1242/dev.01605

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Brent, A. E. Articles by Tabin, C. J. Search for Related Content PubMed PubMed Citation Articles by Brent, A. E. Articles by Tabin, C. J. Social Bookmarking                         What's this?

Genetic analysis of interactions between the somitic muscle, cartilage and tendon cell lineages during mouse development

¹ Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
² Institute of Physiological Chemistry, University of Halle-Wittenberg, Halle, 06099, Germany

View larger version (113K): [in a new window]   Fig. 1. Somitic muscle progenitor specification occurs prior to induction of Scx in the sclerotome. Whole-mount in situ hybridization at E10.5 (A-D) for Scx (A), Myf5 (B), Myod1 (C) and Fgf4 (D). (E-L) Section in situ hybridization for Scx (E,I), Myf5 (F,J), Myod1 (G,K) and Fgf4 (H, L), on alternate sagittal (E-H) or frontal (I-L) sections, through somites of E10.5 embryos. Blue arrows indicate forelimb buds; purple arrows, hindlimb buds; green arrows, branchial arches. Black arrows in E-H indicate onset of expression.

View larger version (86K): [in a new window]   Fig. 2. Induction of Scx in the somite is delayed in Myf5-/- mutant embryos. Whole-mount in situ hybridization for Scx (A,D,G,J), Fgf4 (B,E,H,K) and Myod1 (C,F,I,L) at E10.5 (A-F) and E11.0 (G-L) on Myf5+/- (A-C,G-I) or Myf5-/- (D-F,J-L) embryos. Blue arrows indicate forelimb buds; green arrows, branchial arches; red arrows, interlimb somites.

View larger version (156K): [in a new window]   Fig. 3. Axial tendon progenitor specification and differentiation do not occur in the absence of myotome formation. Whole-mount in situ hybridization for Scx (A,B) and Fgf4 (C,D) at E10.5 on Myf5+/-; Myod1+/- (A,C) or Myf5-/-; Myod1-/- (B,D) embryos. Blue arrows indicate forelimb buds; green arrows, branchial arches. Section in situ hybridization for myogenin (E,F), Scx (G,H,K,L) and tendin (I,J) on transverse sections of E13.5 Myf5+/-; Myod1+/- (E,G,I,K) or Myf5-/-; Myod1-/- (F,H,J,L) embryos. (E-J) Transverse sections through vertebrae and epaxial muscles; (K,L) sections through forelimbs. Section in situ hybridization for myogenin (M,Q), Pea3 (N,R) or Fgf8 (O,S) at E10.5 on Myf5+/-; Myod1+/- (M-O) or Myf5-/-; Myod1-/- (Q-S) embryos. (P,T) Detection of phosphorylated ERK/MAPK on frontal sections at E10.5 on Myf5+/-; Myod1+/- (P) or Myf5-/-; Myod1-/- (T) embryos. Black and yellow arrows in N,P,R,T indicate anterior and posterior sclerotome; blue arrows in O indicate anterior and posterior dermomyotome. Scale bars: 50 µm.

View larger version (76K): [in a new window]   Fig. 4. FGF signaling is necessary and sufficient for induction of Scx in mouse. (A,B) Whole-mount in situ hybridization for Scx on trunks cultured with DMSO (A) or SU5402 (B). (C-F) Whole-mount in situ hybridization for Scx on either wild type (C,D) or Myf5-/-; Myod1-/- (E,F) trunks with either a PBS (C,E) or FGF4 (D,F) bead implanted in somites. (C-F) Asterisks indicate location of beads.

View larger version (189K): [in a new window]   Fig. 5. Spatial and temporal comparison of axial tendon and cartilage progenitor specification and differentiation. Section in situ hybridization for Scx (A,E,I,M,Q,U), Sox9 (B,F,J,N,R,V), and Sox5 (C,G,K,O,S,W). (D,H,L,P,T,X) Alcian Blue staining. (A-D) Alternate frontal sections through thoracic somites at E10.5. Asterisks indicate dorsal root ganglia. (E-H) Alternate transverse sections through thoracic somites at E10.5. (I-L) Alternate transverse sections through vertebrae at E11.5. (M-P) Alternate transverse sections through ribs at E11.5. (Q-T) Alternate transverse sections through vertebrae at E13.5. (U-X) Alternate transverse sections through ribs at E13.5. My, myotome.

View larger version (162K): [in a new window]   Fig. 6. Scx expression is upregulated in the dorsolateral sclerotome of Sox5-/-; Sox6-/- embryos. Section in situ hybridization for Scx (A,D), Sox9 (B,E), lacZ (C,F) or Pea3 (G,J) on frontal sections through thoracic somites of Sox5+/-; Sox6+/- (A-C,G) or Sox5-/-; Sox6-/- (D-F,J) embryos. Red arrow in D indicates upregulation and expansion of Scx expression. (H,K) Tunnel assays at E10.5 on frontal sections of Sox5+/-; Sox6+/- (H) or Sox5-/-; Sox6-/- (K) embryos. (I,L) Detection of phosphorylated ERK/MAPK on frontal sections at E10.5 on Sox5+/-; Sox6+/- (I) or Sox5-/-; Sox6-/- (L) embryos. Yellow arrows indicate anterior and posterior sclerotome; asterisks indicate dorsal root ganglia. My, myotome. Scale bars: 50 µm.

View larger version (140K): [in a new window]   Fig. 7. Scx is expressed throughout the undifferentiated Sox5-/-; Sox6-/- skeletal elements. Section in situ hybridization for Scx (A,D,G,J,M,P,O,R), lacZ (C,F,I,L), and Sox9 (N,Q) on sections through E14.5 Sox5+/-; Sox6+/- (A-C,G-I,M-O) or Sox5-/-; Sox6-/- (D-F,J-L,P-R) embryos. (B,E,H,K) Alcian Blue staining. (O,R) Combined section in situ hybridization and immunohistochemistry for Scx (purple) and myosin heavy chain (brown), respectively. (A-F) Transverse sections through vertebrae. Green arrows indicate vertebral bodies; red arrows, neural arches. (G-R) Transverse sections through ribs.

View larger version (82K): [in a new window]   Fig. 8. In the absence of Sox5 and Sox6, the chondroprogenitors express markers of differentiated tendon. Section in situ hybridization for Scx (A,D), tendin (B,E) and collagen XII (C,F) on alternate transverse sections through ribs of E14.5 Sox5+/-; Sox6+/- (A-C) or Sox5-/-; Sox6-/- (D-F) embryos.

View larger version (18K): [in a new window]   Fig. 9. Summary of interactions between the somitic lineages. Shortly after somite formation, expression of Myf5 and Myod1 appears in the muscle progenitors of the myotome. Following myotome specification, FGFs are activated at the center of the myotome. Myotomal FGFs, secreted from the myotome, signal to the underlying mesenchymal sclerotome, where they induce expression of Scx and tendon progenitor formation within the dorsolateral anterior and posterior sclerotome. The dorsolateral sclerotome also contains chondroprogenitors that are induced to express Sox9 in response to patterning signals, including Shh (and this same Shh signal negatively regulates Scx expression). The Sox9-expressing chondroprogenitors then activate expression of Sox5 and Sox6, which, in turn, are required for chondrocyte differentiation. The dorsolateral mesenchymal sclerotome can thus follow one of two differentiation pathways: axial tendon or cartilage. Sox5 and Sox6 inhibit expression of Scx such that those sclerotome cells undergoing differentiation into cartilage are blocked from adopting a tendon fate. However, in the absence of Sox5 and Sox6, when these same cells are prevented from differentiating into chondrocytes, they switch their fate to tendon and begin expressing markers of both tendon progenitors and differentiated tendons, suggesting that cartilage differentiation is required to actively repress tendon development.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

Twitter