Mouse embryos homozygous for a null mutation in nodal arrest development at early gastrulation and contain little or no embryonic mesoderm. Here, two Xenopus nodal-related genes (Xnr-1 and Xnr-2) are identified and shown to be expressed transiently during embryogenesis, first within the vegetal region of late blastulae and later in the marginal zone during gastrulation, with enrichment in the d...

Mesoderm induction begins during gastrulation. Recent evidence from several vertebrate species indicates mesoderm induction continues after gastrulation in neuromesodermal progenitor cells (NMPs) within the posterior-most embryonic structure called the tailbud. It is unclear to what extent the molecular mechanisms of mesoderm induction are conserved between gastrula and postgastrula stages of d...

Early development of multicellular organisms is marked by a rapid initial increase in their cell numbers, accompanied by spectacular morphogenetic processes leading to the gradual formation of organs of characteristic shapes. During morphogenesis, through differentiation under strict genetic control, cells become more and more specialized. Morphogenesis also requires coordinated cell movement a...

The capacity for extension of the dorsal marginal zone (DMZ) in Pleurodeles waltl gastrulae was studied by scanning electron microscopy and grafting experiments. At the onset of gastrulation, the cells of the animal pole (AP) undergo important changes in shape and form a single layer. As gastrulation proceeds, the arrangement of cells also changes in the noninvoluted DMZ: radial intercalation l...

The evolutionary advent of uterine support of embryonic growth in mammals is relatively recent. Nonetheless, striking differences in the earliest steps of embryogenesis make it difficult to draw parallels even with other chordates. We suggest that use of fertilization as a reference point misaligns the earliest stages and masks parallels that are evident when development is aligned at conserved...

Although gastrulation is regarded as the stage during Drosophila development when the AP patterning system first influences morphological processes, transcription is regulated in complex patterns already at cycle 10. How soon this transcriptional complexity produces spatial differences in morphology has been unclear. We report on two new processes that establish visible morphological inhomogene...

Cell proliferation has generally been considered dispensable for anteroposterior extension of embryonic axis during vertebrate gastrulation. Signal transducer and activator of transcription 3 (Stat3), a conserved controller of cell proliferation, survival and regeneration, is associated with human scoliosis, cancer and Hyper IgE Syndrome. Zebrafish Stat3 was proposed to govern convergence and e...

Gastrulation movements place endodermal precursors, mesodermal precursors and primordial germ cells (PGCs) into the interior of the embryo. Somatic cell gastrulation movements are regulated by transcription factors that also control cell fate, coupling cell identity and position. By contrast, PGCs in many species are transcriptionally quiescent, suggesting that they might use alternative gastru...

Gastrulation was examined in Xenopus embryos injected with various polysaccharides into the blastocoel cavity. The progression of gastrulation was assessed by observing pigmentation and yolk plug size in vegetative view embryos. In heparin- or dextran-sulphate-injected embryos, gastrulation was significantly retarded. This was further confirmed in tissue sections of embryos. In contrast, no suc...

A zinc finger protein that interacts with Xenopus TATA-binding protein was previously isolated by a yeast two-hybrid screen and found to serve as a transcriptional repressor. The gene was designated the negatively regulating zinc finger protein gene (NZFP). Herein, NZFP was found to be expressed maternally. After gastrulation, the level of NZFP mRNA decreased significantly throughout the neurul...