The interface between cell and developmental biology

Cell differentiation, morphology, migration, polarity, intercellular communication and adhesion are all cellular processes that control embryo morphogenesis and lie at the interface of cell and developmental biology. The interface between these two fields is best illustrated, however, in studies of axiation and cytoskeletal remodeling during development. Recent advances reveal novel mechanisms for axiation, including the role of RNA and protein degradation in regulating the timely expression of morphogenetic signals. Significant progress has also been made in identifying components of the cytoskeleton and the extracellular matrix that mediate embryonic cell migration and polarity. Cellular processes at the interface of cell and developmental biology are overseen by the Wnt signaling cascade that coordinates both axiation and cytoskeletal remodeling during development.     

Tracking in cell and developmental biology

The past decade has seen an unprecedented data explosion in biology. It has become evident that in order to take full advantage of the potential wealth of information hidden in the data produced by even a single experiment, visual inspection and manual analysis are no longer adequate. To ensure efficiency, consistency, and completeness in data processing and analysis, computational tools are essential. Of particular importance to many modern live-cell imaging experiments is the ability to automatically track and analyze the motion of objects in time-lapse microscopy images. This article surveys the recent literature in this area. Covering all scales of microscopic observation, from cells, down to molecules, and up to entire organisms, it discusses the latest trends and successes in the development and application of computerized tracking methods in cell and developmental biology.     

The expanding universe of alkaloid biosynthesis

Characterization of many of the major gene families responsible for the generation of central intermediates and for their decoration, together with the development of large genomics and proteomics databases, has revolutionized our capability to identify exotic and interesting natural-product pathways. Over the next few years, these tools will facilitate dramatic advances in our knowledge of the biosynthesis of alkaloids, which will far surpass that which we have learned in the past 50 years. These tools will also be exploited for the rapid characterization of regulatory genes, which control the development of specialized cell factories for alkaloid biosynthesis.     

The developmental biology of Dishevelled: an enigmatic protein governing cell fate and cell polarity

The Dishevelled protein regulates many developmental processes in animals ranging from Hydra to humans. Here, we discuss the various known signaling activities of this enigmatic protein and focus on the biological processes that Dishevelled controls. Through its many signaling activities, Dishevelled plays important roles in the embryo and the adult, ranging from cell-fate specification and cell polarity to social behavior. Dishevelled also has important roles in the governance of polarized cell divisions, in the directed migration of individual cells, and in cardiac development and neuronal structure and function.     

Zebrafish gastrulation movements: bridging cell and developmental biology

During vertebrate gastrulation, large cellular rearrangements lead to the formation of the three germ layers, ectoderm, mesoderm and endoderm. Zebrafish offer many genetic and experimental advantages for studying vertebrate gastrulation movements. For instance, several mutants, including silberblick, knypek and trilobite, exhibit defects in morphogenesis during gastrulation. The identification of the genes mutated in these lines together with the analysis of the mutant phenotypes has provided new insights into the molecular and cellular mechanisms that underlie vertebrate gastrulation movements.     

Vitamin E biosynthesis: biochemistry meets cell biology

Vitamin E is thought to be involved in many essential processes in plants, but no functional proof has been reported. To study vitamin E deficiency in plants, a high-throughput biochemical screen for vitamin E quantification in Arabidopsis mutants has been developed, which has led to the identification of VTE1-encoding tocopherol cyclase. Interestingly, the corresponding maize mutation, sxd1, causes plasmodesmata malfunction, suggesting a link between tocopherol cyclase and plasmodesmata function.     

The developmental biology of cementum.

In conclusion, we have reviewed an extensive literature on early cementogenesis and performed a detailed morphological and molecular analysis to illustrate and verify key issues in the current debate about epithelial and mesenchymal contributions to root cementum. We have demonstrated that prior to cementogenesis, Hertwig's epithelial root sheath disintegrates and dental follicle cells penetrate the epithelial layer to invade the root surface. Our studies confirmed that HERS became disrupted or disintegrated prior to cementum deposition. We visualized how mesenchymal cells from the dental follicle penetrated the HERS bilayer and deposited initial cementum, while immediately adjacent epithelial cells were separated from the root surface by a basal lamina and did not secrete any cementum. Human specimen from the Gottlieb collection indicated that HERS was removed from the root surface prior to cementum deposition. Our in situ hybridization and immolocalization data revealed that both amelogenin mRNAs and enamel proteins were restricted to the crown enamel and were absent from the root surface and from the cervical-most ameloblasts adjacent to the root margin. On Western blots, cementum protein extracts did not cross-react with amelogenin antibodies. Our studies in conjunction with our literature review together confirmed the classical theory of cementum as a dental follicle derived connective tissue that forms subsequent to HERS disintegration.     

The effects of phenobarbital and ketoconazole on the alkaloid biosynthesis in Catharanthus roseus cell suspension cultures

The cytochrome P450 enzyme geraniol 10-hydroxylase plays an important role in the biosynthesis of terpenoid indole alkaloids in suspension cultures of Catharanthus roseus. The activity of this enzyme was induced by the treatment of cells with phenobarbital, and inhibited by treatment with ketoconazole. The alkaloid accumulation increased after phenobarbital treatment whereas it decreased after ketoconazole treatment. Phenobarbital and ketoconazole did not affect the in vivo conversion rate of loganin to secologanin, a reaction proposed to be catalyzed by a cytochrome P450 enzyme.     

The morphogenesis of evolutionary developmental biology

The early studies of evolutionary developmental biology (Evo-Devo) come from several sources. Tributaries flowing into Evo-Devo came from such disciplines as embryology, developmental genetics, evolutionary biology, ecology, paleontology, systematics, medical embryology and mathematical modeling. This essay will trace one of the major pathways, that from evolutionary embryology to Evo-Devo and it will show the interactions of this pathway with two other sources of Evo-Devo: ecological developmental biology and medical developmental biology. Together, these three fields are forming a more inclusive evolutionary developmental biology that is revitalizing and providing answers to old and important questions involving the formation of biodiversity on Earth. The phenotype of Evo-Devo is limited by internal constraints on what could be known given the methods and equipment of the time and it has been framed by external factors that include both academic and global politics.