Highlights in DD

Abstract

“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. Stem cells, from the ground up (Caenorhabditis elegans as a Model for Stem Cell Biology by Pradeep M. Joshi, Misty R. Riddle, Nareg J.V. Djabrayan, and Joel H. Rothman, Dev Dyn 239:1539–1554) C. elegans, may not be the first model system that comes to mind when considering questions of stem cell biology. The organism's only true stem cells are the germline, and it cannot be maintained in cell culture. Nevertheless the amenity of C. elegans to genetic, cell, and molecular manipulations have allowed scientists to use innovative approaches to milk additional information from other cell populations with stem-cell like properties. Epidermal seam cells balance proliferation with differentiation, embryonic progenitor cells progress from a state of pluripotency to cell fate commitment, and the “Y” rectal epithelial cell naturally transforms into a neuron during larval development. This review illustrates how the different cell populations have illuminated mechanisms behind stem cell-niche interactions, self-renewal, cell fate restriction, and transdifferentiation. Although discovered in the lowly worm, many of these themes are proving to be conserved in mammalian systems. Developing a human embryo atlas (Developmental Atlas of the Early First Trimester Human Embryo by Shigehito Yamada, Rajeev R. Samtani, Elaine S. Lee, Elizabeth Lockett, Chigako Uwabe, Kohei Shiota, Stasia A. Anderson, and Cecilia W. Lo, Dev Dyn 239:1585–1595) Many believe that the goal of developmental biology research is to inform human health. However, because our knowledge of human embryogenesis is based largely on drawings and wax models, it lags far behind that of popular model systems, making accurate comparisons impossible. Here, Yamada and colleagues present a much-needed, updated Human Embryo Atlas (http://apps.devbio.pitt.edu/humanatlas/; login: “Human”, password: “Embryo”) encompassing most of the first trimester, when development of major organs and tissues take place. The high-resolution images captured by 21st century techniques—magnetic resonance (MR) imaging and episcopic fluorescence image capture (EFIC)—can be virtually sectioned from any angle, and used to make three-dimensional (3D) reconstructions. The versatile images will help identify potential differences between development of humans and the model organisms that have so far informed our current understanding of vertebrate development, and will facilitate clinical assessments of embryonic health. dalmatian's new trick (Staying Alive: Dalmatian Mediated Blocking of Apoptosis Is Essential for Tissue Maintenance by Bilal E. Kerman and Deborah J. Andrew, Dev Dyn 239:1609–1621) The novel Drosophila nuclear protein Dalmatian (Dmt) was already known for one trick: regulating mitotic spindle assembly. Here, Kerman and Andrew show that dmt also keeps specific cell types from playing dead. In dmt mutants, trachea and salivary gland tubulogenesis is spotty—with networks displaying frequent gaps and breaks. The mutants also show increased expression of the apoptotic activators reaper (rpr) and head involution defective (hid), and the trachea displays enhanced apoptosis during latter stages of morphogenesis (st. 12–14). Dmt salivary gland, and trachea defects are rescued in the background of a deficiency that removes apoptotic inhibitors, and by tissue-specific expression of an anti-apoptotic protein, p35. Of interest, st. 12–14 dmt mutants are sensitized to radiation-induced apoptosis. Because Dmt localizes to heterochromatin, the authors speculate that the protein participates in known epigenetic silencing of rpr and hid during these stages. Dmt's role repressing apoptotic genes probably occurs after cells have ceased dividing, and thus is independent from it's role in mitotic spindle assembly. Always eager to please, Dmt can perform two different tricks.