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“Highlights” calls attention to exciting advances in developmental biology that have recently been reported in Developmental Dynamics. Development is a broad field encompassing many important areas. To reflect this fact, the section spotlights significant discoveries that occur across the entire spectrum of developmental events and problems: from new experimental approaches, to novel interpretations of results, to noteworthy findings utilizing different developmental organisms.

Biasing cell fate (Cell Biological Regulation of Division Fate in Vertebrate Neuroepithelial Cells by Minde I. Willardsen and Brian A. Link, Dev Dyn 240:1865–1879) Among researchers, having a bias toward a certain outcome is considered a no-no. Vertebrate neuroepithelial progenitors, however, do not necessarily feel the same way. During neurogenesis, progenitors are presented with the choice of dividing, or differentiating. Here, Willardsen and Link detail examples where a progenitor's future is influenced by stochastic intrinsic cellular features that lie upstream of transcriptional networks: asymmetric inheritance, cell cycle kinetics, and interkinetic nuclear migration (INM). A single stochastic mechanism, for example inheritance of differently aged centrosomes, can influence whether or not a cell differentiates. The lack of absolute fate restriction suggests that, while each process exerts a fate bias, it's the combination of several biases that ultimately pushes the cell to adopt one fate over the other. This compelling point of view adds an element of uncertainty to experimentation that is not often tolerated by researchers. Disregard the bias toward obtaining straightforward answers; we may need to dig deeper.

It's electric (V-ATPase-Dependent Ectodermal Voltage and pH Regionalization Are Required for Craniofacial Morphogenesis by Laura N. Vandenberg, Ryan D. Morrie, and Dany Spencer Adams, Dev Dyn 240:1889–1904) Recent years have brought forth evidence that the simple proton, H+, regulates particular aspects of development. Vandenberg et al, extend the theme by showing that H+ flux, which alters membrane voltage (Vmem) and/or pH, is important for craniofacial morphogenesis. Both manipulating expression of a H+ vesicular ATPase (V-ATPase) subunit called ductin, and altering Vmem/pH with ductin-independent reagents, cause similar craniofacial abnormalities. Disturbing H+ flux disrupts expression of craniofacial markers but is not toxic overall, and has little affect on neural crest migration or survival, suggesting the effects are direct. Voltage sensitive dyes reveal dynamic hyperpolarization patterns that correlate not only with craniofacial morphogenetic events, but also earlier neurulation-related convergent and extension, and a later change in embryonic shape from spherical to elongated. These observations lead the authors to postulate that bioelectric activity is a mechanism that coordinates differentiation with morphogenesis.

Don't underestimate the yolk sac (Yolk Sac Endoderm Is the Major Source of Serum Proteins and Lipids and Is Involved in the Regulation of Vascular Integrity in Early Chick Development by Fumie Nakazawa, Cantas Alev, Lars M. Jakt, and Guojun Sheng, Dev Dyn 240:2002–2010) Many embryologists view the yolk sac (YS) as something to discard before processing the chicken embryo for in situ hybridization. Here, Nakazawa and colleagues remind us that the YS is an invaluable, complex organ that keeps the embryo alive until its own internal organs mature. For the first time, microarray analysis reveals a close molecular and functional relationship between YS endoderm and definitive endoderm organs. The tissue is highly enriched for genes that regulate lipid, carbohydrate, and amino acid metabolism, suggesting a small intestine-like digestive function. Also prominent are major serum proteins and genes involved in vascular integrity, indicating that, like the liver, it is a major contributor of these components. Taken together with previous findings that mesodermal cues trigger the YS endoderm to differentiate into definitive endodermal cell types, YS endoderm may prove an accessible model for stem cells and for definitive endoderm development. Next time, think twice before tossing the YS.