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Fig. 1. Fibronectin fibrils surround the somitic mesoderm during gastrulation and
extension. A,B: Sagittal sections through the future anterior midline of the early- (A, stage
10 ) and mid-gastrula (B, stage 11 ) show fibronectin fibrils along the neural/mesoderm
interface into the cleft of Brachet (arrowheads) but not at the mesoderm/
endoderm interface (arrows). C: A projection of 251 transverse confocal sections
through the dorsal mesoderm at stage 13 (C) shows that fibronectin appears at the
somitic mesoderm/endoderm interface (arrow) in addition to the neural/somitic
mesoderm boundary (arrowhead). At the same time, fibrils are cleared from the ventral
(v) and are in the process of being cleared from the dorsal (d) surfaces of the
notochord (no). D: Progressive clearing of fibronectin from the notochord is better
seen in projections of en face confocal stacks of an early immature state (D), to a
more connected network (E), and finally to a more tightly connected array surrounding
the somitic mesoderm (F, so) when fibrils are cleared from both surfaces of the
notochord (no). G: Projections of subsets of slices from a single en face stack containing
only the neural/mesoderm boundary (G) or the mesoderm/endoderm boundary (H) show distinct fibrils, whereas a projection of confocal sections through the middle of the mesoderm (shown overexposed in I) show fibrils at the lateral walls of the notochord (no) and small fibronectin-rich puncta within the somitic mesoderm (so). J: Ontogeny of the fibrillar fibronectin matrix. A ut-awaytransverse view of fibrillar fibronectin matrix assembly from mid- to late-gastrula stages. bp, blastopore; ne, neural ectoderm; en, endoderm; a, anterior; p, posterior. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.] |
