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Henry, JQ, Lyons DC.  2016.  Molluscan models: Crepidula fornicata. Current Opinion in Genetics & Development. 39:138-148.   10.1016/j.gde.2016.05.021   AbstractWebsite

Gastropod snails in the genus Crepidula have emerged as model systems for studying a metazoan super clade, the Spiralia. Recent work on one species in particular, Crepidula fornicata, has produced high-resolution cell lineage fate maps, details of morphogenetic events during gastrulation, key insights into the molecular underpinnings of early development, and the first demonstration of CRISPR/Cas9 genome editing in the Spiralia. Furthermore, invasive species of Crepidula are a significant ecological threat, while one of these, C. fornicata, is also being harvested for food. This review highlights progress towards developing these animals as models for evolutionary, developmental, and ecological studies. Such studies have contributed greatly to our understanding of biology in a major clade of bilaterians. This information may also help us to control and cultivate these snails.

Moczek, AP, Sears KE, Stollewerk A, Wittkopp PJ, Diggle P, Dworkin I, Ledon-Rettig C, Matus DQ, Roth S, Abouheif E, Brown FD, Chiu CH, Cohen CS, De Tomaso AW, Gilbert SF, Hall B, Love AC, Lyons DC, Sanger TJ, Smith J, Specht C, Vallejo-Marin M, Extavour CG.  2015.  The significance and scope of evolutionary developmental biology: a vision for the 21st century. Evolution & Development. 17:198-219.   10.1111/ede.12125   AbstractWebsite

Evolutionary developmental biology (evo-devo) has undergone dramatic transformations since its emergence as a distinct discipline. This paper aims to highlight the scope, power, and future promise of evo-devo to transform and unify diverse aspects of biology. We articulate key questions at the core of eleven biological disciplinesfrom Evolution, Development, Paleontology, and Neurobiology to Cellular and Molecular Biology, Quantitative Genetics, Human Diseases, Ecology, Agriculture and Science Education, and lastly, Evolutionary Developmental Biology itselfand discuss why evo-devo is uniquely situated to substantially improve our ability to find meaningful answers to these fundamental questions. We posit that the tools, concepts, and ways of thinking developed by evo-devo have profound potential to advance, integrate, and unify biological sciences as well as inform policy decisions and illuminate science education. We look to the next generation of evolutionary developmental biologists to help shape this process as we confront the scientific challenges of the 21st century.

Lyons, DC, Martik ML, Saunders LR, McClay DR.  2014.  Specification to biomineralization: Following a single cell type as it constructs a skeleton. Integrative and Comparative Biology. 54:723-733.   10.1093/icb/icu087   AbstractWebsite

The sea urchin larva is shaped by a calcite endoskeleton. That skeleton is built by 64 primary mesenchyme cells (PMCs) in Lytechinus variegatus. The PMCs originate as micromeres due to an unequal fourth cleavage in the embryo. Micromeres are specified in a well-described molecular sequence and enter the blastocoel at a precise time using a classic epithelial-mesenchymal transition. To make the skeleton, the PMCs receive signaling inputs from the overlying ectoderm, which provides positional information as well as control of the growth of initial skeletal tri-radiates. The patterning of the skeleton is the result both of autonomous inputs from PMCs, including production of proteins that are included in the skeletal matrix, and of non-autonomous dynamic information from the ectoderm. Here, we summarize the wealth of information known about how a PMC contributes to the skeletal structure. The larval skeleton is a model for understanding how information encoded in DNA is translated into a three-dimensional crystalline structure.

McIntyre, DC, Lyons DC, Martik M, McClay DR.  2014.  Branching out: Origins of the sea urchin larval skeleton in development and evolution. Genesis. 52:173-185.   10.1002/dvg.22756   AbstractWebsite

It is a challenge to understand how the information encoded in DNA is used to build a three-dimensional structure. To explore how this works the assembly of a relatively simple skeleton has been examined at multiple control levels. The skeleton of the sea urchin embryo consists of a number of calcite rods produced by 64 skeletogenic cells. The ectoderm supplies spatial cues for patterning, essentially telling the skeletogenic cells where to position themselves and providing the factors for skeletal growth. Here, we describe the information known about how this works. First the ectoderm must be patterned so that the signaling cues are released from precise positions. The skeletogenic cells respond by initiating skeletogenesis immediately beneath two regions (one on the right and the other on the left side). Growth of the skeletal rods requires additional signaling from defined ectodermal locations, and the skeletogenic cells respond to produce a membrane-bound template in which the calcite crystal grows. Important in this process are three signals, fibroblast growth factor, vascular endothelial growth factor, and Wnt5. Each is necessary for explicit tasks in skeleton production. genesis 52:173-185. (c) 2014 Wiley Periodicals, Inc.

Cheng, XR, Lyons DC, Socolar JES, McClay DR.  2014.  Delayed transition to new cell fates during cellular reprogramming. Developmental Biology. 391:147-157.   10.1016/j.ydbio.2014.04.015   AbstractWebsite

In many embryos specification toward one cell fate can be diverted to a different cell fate through a reprogramming process. Understanding how that process works will reveal insights into the developmental regulatory logic that emerged from evolution. In the sea urchin embryo, cells at gastrulation were found to reprogram and replace missing cell types after surgical dissections of the embryo. Non-skeletogenic mesoderm (NSM) cells reprogrammed to replace missing skeletogenic mesoderm cells and animal caps reprogrammed to replace all endomesoderm. In both cases evidence of reprogramming onset was first observed at the early gastrula stage, even if the cells to be replaced were removed earlier in development Once started however, the reprogramming occurred with compressed gene expression dynamics. The NSM did not require early contact with the skeletogenic cells to reprogram, but the animal cap cells gained the ability to reprogram early in gastrulation only after extended contact with the vegetal halves prior to that time. If the entire vegetal half was removed at early gastrula, the animal caps reprogrammed and replaced the vegetal half endomesoderm. If the animal caps carried morpholinos to either hox11/13b or foxA (endomesoderm specification genes), the isolated animal caps failed to reprogram. Together these data reveal that the emergence of a reprogramming capability occurs at early gastrulation in the sea urchin embryo and requires activation of early specification components of the target tissues. (C) 2014 Elsevier Inc. All rights reserved.