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Fig. 3. Fibril assembly and remodeling during neural fold formation and neural tube closure. A: Transverse confocal sections were
collected and assembled into montages of dorsal axial tissues from the flat neural plate stage (A) to tadpole stage (J). A,B: Fibronectinrich
fibrils localize to the ventral and dorsal surfaces of the somitic mesoderm of early neural fold stages (stage 14) but are absent from
the boundary between lateral plate and ventral mesoderm and endoderm (arrowheads in A). C: Fibrils are restored to the dorsal surface
of the notochord (arrowhead) where notoplate cells attach. Archenteron roof plate cells contact the notochord along the fibril-free
ventral surface (arrow in C). D: Somite morphogenesis continues and the neural plate converges toward the midline as a deep neural
groove forms. E: Fibrils are assembled under the ventral surface of the notochord (arrow) as the neural folds (asterisk) appose one
another. F: By the time the neural folds have fused, fibronectin-rich fibrils are formed along the inner surface of the lateral plate and ventral
mesoderm (arrowheads). G,H: Fibrils, mostly absent from the dorsal surface of the neural tube (arrowheads in G), are assembled as the
neural tube lumen (asterisk in H) is reestablished. I: By late tail bud stage, fibrils sheath the neural tube, notochord, and somites, including
the intersomitic clefts (arrows) shown in this section. I,J: From late tail bud (I) to tadpole stages (J) fibrils are extensively assembled in the
fin (arrowheads) and contact both the dorsal surface of the neural tube and the dorsal-most surface of somites. ar, archenteron; d, dorsal;
ec, ectoderm; en, endoderm; ne, neural plate ectoderm; no, notochord; nt, neural tube; so, somitic mesoderm; v, ventral. |
