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An archetype of collaboration, community development and vision, who made fundamental contributions to biology through his studies on the often-unseen part of the plant, the root.

The authors show that metabolic activity leads to an increase in the intracellular pH of neuromesodermal precursors, and that this increase in pH, by allowing post-translational modification of β-catenin, is required for the activation of WNT signalling and mesodermal fate acquisition.

A protocol for differentiating mouse and human pluripotent stem cells into muscle.

An embryo’s body plan is established by a structure called the organizer. Evidence of this structure in humans has been lacking, but a stem-cell-based protocol has now enabled researchers to demonstrate its existence.

An in vitro system that recapitulates temporal characteristics of embryonic development demonstrates that the different rates of mouse and human embryonic development stem from differences in metabolic rates and—further downstream—the global rate of protein synthesis.

Somitoids and segmentoids—culture systems that recapitulate the formation of somite-like structures—reveal that an initial salt-and-pepper expression pattern of MESP2 in a newly formed segment is transformed into compartments of anterior and posterior identity through an active cell-sorting mechanism.

Established during embryogenesis, vertebrate segmentation is most conspicuous at the level of the periodic arrangement of vertebrae in the spine. Since the identification of the segmentation clock, which is a travelling oscillator, the generation of segmental pattern in the presomitic mesoderm has been a particular focus of attention.

Human presomitic mesoderm cells derived in vitro demonstrate oscillations of the segmentation clock, thus providing a window into an otherwise inaccessible stage of human development.

Most animal embryos grow through cell accumulation in a posterior growth zone, but the underlying forces are unknown. It is now proposed that posterior elongation in chicken embryos is an emergent property that arises from graded cell motility in random directions (as opposed to directed movement). This occurs in response to signalling through the fibroblast growth factor.

The vertebrate body plan shows marked bilateral symmetry, although this can be disrupted in conditions such as scoliosis. Here, a mutation in Rere is found that leads to the formation of asymmetrical somites in mouse embryos; furthermore, Rere is shown to control retinoic acid signalling, which is required to maintain somite symmetry by interacting with Fgf8. The results provide insight into how bilateral symmetry is maintained.

Retinoic acid (RA) regulates the maintenance of somitogenesis symmetry. Here, the authors use a proteomic approach to identify a protein complex of Wdr5, Hdac1, Hdac2 that act together with RA and coactivator Rere/Atrophin2 and a histone methyltransferase Ehmt2 to regulate embryonic symmetry.

Somite formation relies on a molecular oscillator, the segmentation clock, which leads to oscillatory gene expression in the presomitic mesoderm; this is converted into the periodic generation of segments in response to signalling gradients referred to as the wavefront. Recent studies provide insights into the molecular mechanisms behind this intricate developmental system.

A model of the embryonic human trunk attains a more mature developmental stage than previous models.

Hox genes are first activated in precursor cells of somites, where they control the migratory properties of these cells, and the timing of their ingression and final position in the developing vertebrate column.

The vertebrate body axis is divided into a number of segments or 'somites', such as the number of vertebrae. But what controls vertebra number, and its variation between species? This paper postulates that the number depends on a balance between the division of the body into somites (the segmentation clock rate) and the overall rate of development, as established by showing that the large number of vertebrae in snakes comes from a much greater segmentation clock speed in snakes, relative to development as a whole, than in other vertebrates.

The organization of Hox clusters in several different reptiles is investigated, showing that the Hox clusters in squamates — lizards and snakes — have unexpectedly accumulated transposable elements, reflecting extensive genomic rearrangements of coding and non coding regulatory regions. Comparative expression analyses between two species showing different axial skeletons, the corn snake and the whiptail lizard, revealed major alterations in Hox13 and Hox10 expression features during snake somitogenesis, in line with the expansion of both caudal and thoracic regions.

The 'mosaic' theory of development applies, to different degrees, to most animals. It owes its existence in part to a group of obscure marine invertebrates, which now take centre stage in the molecular age.

A detailed theoretical and experimental investigation of homogeneous cell tissues finds that they can undergo spontaneous spatial symmetry breaking through a purely electrophysiological mechanism.

Pluripotent stem cells are being used to generate models of early embryogenesis that are promising for discovery and translational research. To be useful, these models require critical consideration of their level of efficiency and fidelity to natural embryos. Here we propose criteria with which to raise the standards of stem-cell-based embryo models of human embryogenesis.

Muscle development in vertebrates relies on signals transmitted from proteins of the Wnt family. But which molecules form the relay that transfers this signal to the cell nucleus? The answer is unexpected.

Somite formation, crucial for organization of the segmental pattern of vertebrate embryos, depends on the oscillatory expression of segmentation clock genes. Novel in vitro models of somitogenesis have provided insights into the spatiotemporal dynamics of gene expression, signalling and metabolic gradients that enable somite formation and patterning.

This protocol uses dual modulation of Wnt and BMP signaling pathways to differentiate human pluripotent stem cells into striated, millimeter-long muscle fibers and satellite-like cells in vitro without the need to introduce genetic material or cell sorting.

It has been known for some time that limbs share at least some of their molecular patterning mechanism with external genitalia; here, this connection is examined in a variety of species, revealing that once-shared developmental trajectories could help to explain the observed patterning similarities.