spacer gif spacer gif spacer gif spacer gif spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

This Article
Right arrow Summary Freely available
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Ashique, A. M.
Right arrow Articles by Richman, J. M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Ashique, A. M.
Right arrow Articles by Richman, J. M.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati   Add to Twitter  
What's this?

Endogenous bone morphogenetic proteins regulate outgrowth and epithelial survival during avian lip fusion

Amir M. Ashique*, Katherine Fu and Joy M. Richman{dagger}

Department of Oral Health Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver BC, Canada
* Present address: The Forsyth Institute, Harvard School of Dental Medicine, 140 Fenway Avenue, Boston, MA, USA



View larger version (97K):

[in a new window]
  		Fig. 1. Expression of BMPs and Noggin at the time of fusion of the primary palate. (A-D) Expression of Bmp2, (E-H) expression of Bmp4, (I-L) expression of Bmp7, (M,N,P,Q) expression of Noggin. Plane of section for midsagittal sections (B,F,J,N,O) is the broken line in (A), plane of section for frontal sections is the broken line in B. (O) Expression of Shh. Bottom row was photographed in brightfield; silver grains appear black on a white background. (A,C) Expression of Bmp2 is high in the facial mesenchyme at the zone of fusion (arrows in A). Some epithelial signal can also be seen in (D). (E,G,H) Bmp4 is expressed primarily in epithelium in the maxilla and frontonasal mass. (I,K) Bmp7 is expressed in all epithelia at high levels as well as the inferior mesenchyme of the frontonasal mass (arrows). (M) Noggin is expressed at the caudal edge of the frontonasal mass at stage 24, including the lateral corners (globular processes, arrow); however, at stage 28 expression is lost at the corners (arrow, P). (F,N) Sagittal sections close to the midline show that Noggin and Bmp4 distinguish the frontonasal mass epithelium from that of stomodeal and general surface epithelium, whereas Shh is expressed in stomodeal epithelium up to the edge of the oral epithelium (O). The edges of the Noggin expression domain in relation to those of Bmp4 and Shh are indicated by arrowheads (F,O). (D,H,L) Higher-power views of the region of contact between the frontonasal mass and maxillary prominence highlight epithelial expression of all three Bmps and no expression of Noggin (Q). Scale bars: 500 µm for dark field images;100 µm for brightfield images. Abbreviations: fnm, frontonasal mass; lnp, lateral nasal prominence; md, mandibular prominence; mx, maxillary prominence.

 


View larger version (87K):

[in a new window]
  		Fig. 2. Effects of Noggin on facial morphogenesis. (A) Lateral view and (B) palatal view of a normal skull with mandible removed. The palatine bone extends and contacts the triangular maxillary bone. The jugular process of the maxillary bone extends dorsally and contacts the jugal bone. (C) Embryo treated with one Noggin bead in maxillary prominence at stage 22 and two beads in the globular process at stage 26. Lateral view with mandible attached, showing bifurcated maxillary bone (asterisk). The palatine process of the maxillary bone is connected to the superior branch of the duplicated bone. (D) Palatal view of embryo in (C), showing truncation of palatine bone (asterisk) on the right-hand side. Maxillary bone and premaxilla are outside the field of view towards the right. (E) A side view of the stage 36 beak, showing a disruption in the normally smooth edge (arrow). The absence of palatal shelves can be seen on the treated side. The beak has extended fully, a premaxilla is present and the outer surface is capped with an egg tooth. (F) Palatal view of embryo treated with four beads of Noggin. Asterisk indicates absent maxillary bone. There is also no palatine bone present on the right-hand side. (G) Frontal SEM view of a stage 28 embryo, 12 hours after the second set of beads was implanted. The decreased size of the maxilla on the treated side is evident (arrow), as well as a slight reduction of the globular process of the frontonasal mass (asterisk). (H) Superior view of stage 30 face treated with four beads. Fusion has not occurred on the right, treated side (arrow), whereas normal development is taking place on the contralateral side. (I) Treated and (J) control sides of an embryo stained with BrdU antibody and counterstained with Malachite Green. Dashed line in (I) indicates a zone of low proliferation. (K) Decrease in msx1 expression in the maxillary prominence six hours after the first set of beads (arrow, stage 22+) and (L) 12 hours after the second set of beads (lower arrow, stage 28). Frontonasal mass expression has started to recover in the older embryo (upper arrow). (M) Increased expression in the mesenchyme 12 hours after the first set of beads (arrows, stage 22+). (N) Increased expression in the globular process on the treated side 12 hours after the second set of beads (arrow, stage 28). Scale bars: 3 mm in A-D,F (bar in C can be used for D); 500 µm for E,G,H,K,L,M,N; 100 µm for I,J. Abbreviations: et, egg tooth; fnm, frontonasal mass; j, jugal; lnp, lateral nasal prominence; md, mandibular prominence; mx, maxillary prominence, mxb, maxillary bone, n, nasal bone, nc, nasal chonchae, p, palatine bone, pmx, premaxilla, pp, palatine process of the maxillary bone, ps, palatal shelf.

 


View larger version (80K):

[in a new window]
  		Fig. 3. Effects of Noggin on epithelial survival. (A) Brightfield and (B) fluorescence view of a Noggin-treated embryo showing a decrease in Acridine Orange staining near the bead (arrowheads). (C) Treated and (D) control sides of the frontonasal mass showing an increased thickness in the epithelium (arrow in C, stage 26). (E) Decrease in expression in epithelium and mesenchyme six hours after the first set of beads (arrow, stage 22+). (F) Increase in size and intensity of expression domain near bead (arrow), 12 hours after second set of beads, stage 28. (G) No change in Shh expression 12 hours after the first set of beads were applied (stage 24, arrow). (H) Increase in Shh expression in the epithelium (arrowheads) of the globular process (upper arrow) and of the anterior-medial maxillary prominence (stage 29). On the contralateral side there is no expression of Shh in the globular process or in the anterior-medial maxillary prominence (lower arrow). Scale bars: 0.5 mm for A,B,E-H; 100 µm for C,D. Abbreviations: b, bead; fnm, frontonasal mass; mx, maxillary prominence.

 


View larger version (81K):

[in a new window]
  		Fig. 4. Effects of BMP2 on facial morphogenesis. (A) SEM showing the reduction in size of the frontonasal mass (arrow). (B) Loss of the maxillary bone (asterisk) and the abnormal articulation of the palatine bone to the jugal bone (arrow). (C) Upregulation of Msx1 expression in frontonasal mass (arrow) and maxillary prominence. (D) Expression of Msx2 encompasses one-third of the maxillary prominence (lower arrow) and the lateral third of the frontonasal mass (upper arrow). Normal expression domain of Msx2 in the maxilla is restricted to a small patch at the posterior edge of the prominence (arrowhead). (E) Downregulation of Shh expression in the epithelium of the stomodeum (arrows). (F) Slight decrease in Shh expression after only 3 hours of BMP2 treatment (stage 24). Note the lack of expression in the globular process on the contralateral side. (G) Decrease in expression of Fgf-8 around the treated nasal pit (arrow). Position of bead is shown with asterisk in D-G. Scale bars: 500 µm for A,C-G (bar in C applies to C-E); 3 mm for B. Abbreviations: fnm, frontonasal mass; mx, maxillary prominence; mxb, maxillary bone; md, mandibular prominence; j, jugal; p, palatine bone.

 


View larger version (132K):

[in a new window]
  		Fig. 5. Effect of exogenous BMP2 and epithelial stripping on programmed cell death and the effect of BMP2 on Noggin expression. Embryos in (A-I,K,L) were treated with 0.84 mg ml–1 BMP2. Embryo in J was treated with Nile Blue Sulfate and the epithelium was stripped. (A,D,G,J) High power views of the globular process on the treated side. (A-C) Four hours after the bead was implanted, there is very little cell death induced around the bead (A,B). Noggin expression is increased in the epithelium and in the mesenchyme in an adjacent section (arrowhead, C). (D,E) TUNEL-reacted sections show increase in programmed cell death in the epithelium of the frontonasal mass (arrowheads) and in the mesenchyme lateral to the bead. (F) Expression of Noggin is increased in the epithelium extending up into the nasal pit and maxillary epithelia (arrowheads). A gradient of increased Noggin expression with lower expression near the bead and higher expression further from the bead (arrow). This pattern is complementary to the programmed cell death shown in E. The peak increase in programmed cell death is seen at 12 hours (G,H) and a decrease in size of the globular process is already evident (arrowhead). (I) Areas of lower Noggin expression partly overlap areas of cell death medial to the bead. (K) TUNEL reaction is nearly absent on the right-hand side, 24 hours after bead implantation. (L) Noggin expression remains high in the epithelium and in the mesenchyme on the treated side of the frontonasal mass. (J) TUNEL reaction on an embryo 10 hours after frontonasal mass epithelium was stripped. There is increased programmed cell death in a localized region of the globular process (arrow). Scale bars: 100 µm for A,D,G,J; 500 µm for B,C,E,F,H,I,K,L. Abbreviations: b, bead; epi, epithelium; fnm, frontonasal mass; lnp, lateral nasal prominence; md, mandibular prominence; mx, maxillary prominence.

 


View larger version (45K):

[in a new window]
  		Fig. 6. Diagrammatic representation of signals that operate in the epithelium and in the mesenchyme within the globular process and maxillary prominence at the time of primary palate fusion. (A) Region illustrated in (B) is enclosed in box. (B) The differences in expression of genes in the epithelium in relation to possible mesenchymal signals are illustrated. Coloured boxes indicate gene families that are expressed in different regions of the epithelium. Abbreviations: EMT, epithelial-mesenchymal transformation; FNM, frontonasal mass; LNP, lateral nasal prominence; Mx, maxillary prominence; NP, nasal pit; PCD, programmed cell death.

 

Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati   Add to Twitter Twitter    What's this?



© The Company of Biologists Ltd 2002