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


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

First published online 3 July 2006
doi: 10.1242/dev.02465

Development 133, 2937-2946 (2006)
Published by The Company of Biologists 2006
This Article
Right arrow Summary Freely available
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Supplementary Material
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 Gutin, G.
Right arrow Articles by Hébert, J. M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Gutin, G.
Right arrow Articles by Hébert, 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?

FGF signalling generates ventral telencephalic cells independently of SHH

Grigoriy Gutin1,*, Marie Fernandes1,*, Laura Palazzolo1, HunKi Paek1, Kai Yu2, David M. Ornitz2, Susan K. McConnell3 and Jean M. Hébert1,{dagger}

1 Departments of Neuroscience and Molecular Genetics, Albert Einstein College of Medicine, 1410 Pelham Parkway South, Bronx, NY 10461, USA.
2 Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA.
3 Department of Molecular Biology and Pharmacology, Washington University, St Louis, MO 63110, USA.


Figure 1
View larger version (71K):

[in a new window]
  		Fig. 1. All three FGFR double mutants are generated. (A) Crosses designed to obtain the three possible combinations of FGFR double mutants. The Fgfr1 and Fgfr2 mutant alleles are floxed, whereas the Fgfr3 allele is a null. The embryos homozygous mutant for Fgfr2 and Fgfr3 are also heterozygous mutant for Fgfr1. Whole E12.5 control (B) and Fgfr1;Fgfr2 double mutant (C) embryos. The mutant, as well as having a smaller telencephalon (arrow), loses the frontonasal process (arrowhead).

 

Figure 2
View larger version (112K):

[in a new window]
  		Fig. 2. Ventral cell types are lost in FGFR double mutants. RNA in situ hybridization analysis of E12.5 coronal brain sections using radioactive probes. (A,E,I) In the control embryo, expression of Pax6 (A), Dlx2 (E) and Nkx2.1 (I) are used to identify the dorsal, ventral and ventromedial areas of the telencephalon. (B,F,J) In the Fgfr2-/-;Fgfr3-/- mutant, dorsoventral patterning and morphology of the telencephalon are grossly normal. (C,G,K) In the Fgfr1-/-;Fgfr3-/- mutant, although the borders of expression of Pax6 (C), Dlx2 (G) and Nkx2.1 (K) are normal (arrowheads), indicating proper dorsoventral specification of precursor cells, the morphology of the ventral telencephalon is abnormal and flattened in appearance. (D,H,L)In the Fgfr1-/-;Fgfr2-/- mutant, ventral precursor cells are lost, indicated by expression of Pax6 that extends to the ventral midline (D) and by the loss of Dlx2 (H) and Nkx2.1 (L) expression.

 

Figure 3
View larger version (64K):

[in a new window]
  		Fig. 3. Cell fate, proliferation, and death are perturbed in the Fgfr1-/-; Fgfr2-/- mutant. (A,B) BrdU incorporation and TUNEL analyses of E10.5 control and mutant telencephalons. Slightly lower rates of BrdU incorporation in the ventral telencephalon (A) and higher rates of cell death in the dorsal midline (B) are observed in the Fgfr1-/-;Fgfr2-/- mutant compared with controls. (C-F) Whole-mount in situ hybridization. The more anterior domain of Nkx2.1 expression in the forebrain is absent as early as E9.25 in the mutant. Arrowheads indicate the putative telencephalic-diencephalic ventral border. OS, optic stalk.

 

Figure 4
View larger version (109K):

[in a new window]
  		Fig. 4. Neurogenesis is perturbed in the Fgfr1-/- ;Fgfr3-/- and Fgfr1-/- ; Fgfr2-/- mutants. (A-L) RNA in situ hybridization analysis of E12.5 coronal brain sections using radioactive probes. Shh and Lhx7 are normally expressed in differentiating cells of the medial ganglionic eminence (A,D); however, this expression is lost in the mutants (B,C,E,F). Ebf1, on the other hand, which is normally expressed in differentiating cells of the lateral ganglionic eminence (G), remains expressed in the Fgfr1-/-;Fgfr3-/- mutant (H), but not the Fgfr1-/-;Fgfr2-/- mutant (I). Mash1, which is normally expressed in ventral precursors (J), remains expressed in the Fgfr1-/-;Fgfr3-/- (K) but not the Fgfr1-/-;Fgfr2-/- (L) mutant. (M-S) RNA in situ hybridization of E16.5 coronal brain sections. Gad67 expression is lost in Foxg1-expressing areas (arrows) of the Fgfr1-/-;Fgfr2-/- mutant at the expense of Tag1 expression (O,R,S), whereas in the Fgfr1-/-;Fgfr3-/- mutant, the boundaries of Gad67 and Tag1 expression are normal (M,N,P,Q). Scale bars: 0.5 mm in A-L; 1 mm in M-S.

 

Figure 5
View larger version (67K):

[in a new window]
  		Fig. 5. The Fgfr1-/-;Fgfr3-/- SVZ is expanded and undergoes more cell death and less cell cycle exit. (A-C) RNA in situ hybridization of E12.5 coronal sections through the ventromedial area. Unlike the control, Prox1 expression in the mutant expands from the SVZ to the ventricular surface (A). This expansion coincides with an apparent decrease in the expression of the VZ markers Hes5 and Lhx2 (B,C). Scale bar: 0.02 mm. (D) Control and mutant E11.5 brains doubled-labelled for Ki67 and BrdU (injected 24 hrs prior to sacrifice). (E) A larger percentage of Ki67+BrdU labelled cells over total BrdU-labelled cells is present in the mutant compared with the control, indicating an abnormally low rate of cell cycle exit. TUNEL analysis (F) indicates a higher rate of cell death in the mutant at E11.5.

 

Figure 6
View larger version (91K):

[in a new window]
  		Fig. 6. SHH signalling is insufficient to generate ventral precursors in the Fgfr1-/-;Fgfr2-/- mutant. (A) Whole-mount RNA in situ hybridization analysis of E10.5 control and Fgfr1-/-;Fgfr2-/- mutant embryos indicates that Shh remains expressed in the mutant in the ventral mesendoderm underlying the telencephalon (arrowheads). (B,C) RNA in situ hybridization analysis of serial E10 coronal sections through the anterior prosencephalon. In telencephalic areas expressing Foxg1 (B), expression of Gli1, which requires SHH activity, is localised to the ventral areas of the mutant (C, arrows).

 

Figure 7
View larger version (132K):

[in a new window]
  		Fig. 7. Loss of Gli3 does not rescue the Fgfr1-/-;Fgfr2-/- phenotype. (A-D) E12.5 whole embryos. Development of the telencephalon is severely compromised in the Fgfr1-/-;Fgfr2-/-;Gli3-/- mutant (D) compared with the other genotypes (A-C). t, telencephalon; d, diencephalon. (E-U) RNA in situ hybridization analysis of E12.5 coronal brain sections. In the Fgfr1-/-;Fgfr2-/-;Gli3+/- mutant, as in the Fgfr1-/-;Fgfr2-/- mutant, Pax6 and Emx2 expression extends to the ventromedial area of the telencephalon at the expense of ventral markers such as Dlx2 (E-M). The remaining expression of Dlx2 in both mutants (L,M) is likely to be hypothalamic rather than telencephalic as it coincides with areas with decreased or absent Foxg1 expression in neighbouring sections (not shown). In the Fgfr1-/-;Fgfr2-/-;Gli3-/- mutant, Foxg1-positive areas express Pax6 but not Dlx2 (N-P). Wnt3a expression in the cortical hem appears normal for all genotypes except Fgfr1-/-;Fgfr2-/-;Gli3-/- (Q-U). Broken lines indicate the Foxg1-positive telencephalic area in an exencephalic mutant (T,U). Scale bar: 0.5 mm in E-U.

 

Figure 8
View larger version (55K):

[in a new window]
  		Fig. 8. Model for the generation of ventral and midline cell types in the telencephalon. SHH, which is expressed ventral to the developing telencephalon, is required to generate not only ventral cell types, but also rostral and dorsal midline ones. SHH is likely to be required for these processes only indirectly by antagonizing GLI3 and thus relieving repression of Fgf gene expression (see Discussion). FGFs are then necessary to generate ventral and at least some rostral midline cell types. Previous evidence indicates that GLI3 is required for expression of WNTs and BMPs and for formation of the dorsal midline, and that FGF8 regulates Bmp4 expression in a dose-dependent manner. Hence, SHH is likely to promote ventral and midline development indirectly by regulating GLI3 and FGF signalling.

 

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 2006