Cell intercalation and cell shape changes drive notochord morphogenesis in the African frog, Xenopus laevis. Experimental observations show that cells elongate mediolaterally and intercalate between one another, causing the notochord to lengthen and narrow. Descriptive observations provide few clues as to the mechanisms that coordinate and drive these cell movements. It is possible that a few r...

Danforth'sshort-tail (Sd) mouse is a semi-dominant mutation affecting the development of the vertebral column. Although the notochord degenerates completely by embryonic day 9.5, the vertebral column exists up to the lumber region, suggesting that the floor plate can substitute for notochord function. We previously established the mutant mouse line, Skt(Gt), through gene trap mutagenesis and id...

Two axial structures, a neural tube and a notochord, are characteristics of chordates and therefore, information about developmental mechanisms of the neural tube and the notochord in lower chordates is essential for an understanding of the origin of the chordate body plan (Satoh and Jeffery, 1995). The neural tube of ascidian larvae is composed of about 340 cells, and is divided into three reg...

The notochord is a structure present in all chordates and its development requires the transcription of Brachyury. While previous studies have shown that Brachyury is essential for notochord formation in vertebrate embryos, this gene is also expressed during the embryogenesis of nonchordate deuterostomes, hemichordates and echinoderms. Here we report that nonchordate deuterostome Brachyury gene...

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Notochord vacuoles make a rod for the ver tebrate back T he rod-shaped notochord is one of the fi rst prominent structures to form in the early embryo, and its evolutionary development was a key advance that allowed early chordates to grow larger and swim in the primordial oceans. In modern vertebrates, the notochord consists of two cell layers: an inner core of cells that each contain a large,...

The bilateral organization of the vertebrate nervous system is underlain, ontogenically as well as topologically, by the notochord. Derived from mid-dorsal mesoderm, the notochord is a compression-resisting rod that plays a supporting role as the axial skeleton in larval or embryonic vertebrates and later as a template for the basicranium and vertebrae. Earlier in development, the notochord pla...

Brachyury plays a pivotal role in the notochord formation in ascidian embryos. Ciona intestinalis Noto4 (Ci-Noto4) was isolated as a gene downstream of Ci-Bra. This gene encodes a 307 amino-acid protein with a C-terminal phosphotyrosine interaction domain (PTB/PID). Expression of Ci-Noto4 commences at the neural plate stage and is specific to notochord cells. Suppression of Ci-Noto4 levels with...

Cell elongation is a fundamental process that allows cells and tissues to adopt new shapes and functions. During notochord tubulogenesis in the ascidian Ciona intestinalis, a dramatic elongation of individual cells takes place that lengthens the notochord and, consequently, the entire embryo. We find a novel dynamic actin- and non-muscle myosin II-containing constriction midway along the antero...