For evolution to occur, developmental processes must be modified. However, the relationship between development and evolution is only beginning to receive experimental study. We have defined an experimental system that allows us to study the evolution of pathways of early development. The proposed research is to investigate the changes in cellular behavior and gene expression that accompany a radical evolutionary change from the ancestral indirect mode of development of typical sea urchins to direct development. The experimental system is a molecular and developmental comparison of a direct developing sea urchin, Heliocidaris erythrogramma, to two closely related typical developing species, H. tuberculata and Strongylocentrotus purpuratus. The major problem to be addressed is how the two developmental pathways diverge at the end of gastrulation. The gastrula of H. erythrogramma resembles that of H. tuberculata, but at the end of gastrulation it begins to generate the precursors of the juvenile adult sea urchin. In contrast the indirect developing pathway at this point begins to generate the feeding pluteus larva. Only much later will adult structures be made. The proposed project has three specific aims: (1) determination of relative roles for cell autonomous versus cell-cell communication in the evolution of early development; (2) identification of regulatory genes that underly the evolutionary divergence of developmental pathways at gastrulation; (3) initiation of studies to experimentally generate evolutionary changes in early development. The study of the evolution of developmental processes offers a means to explore how differences between species arise in the course of evolution. Closely related species that differ in significant ways in developmental pattern provide us with natural varients of developmental processes. The study of these closely related but developmentally distinct species allows mechanisms underlying changes to be identified and their functions determined.

National Institute of Health (NIH)
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
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Cellular Biology and Physiology Subcommittee 1 (CBY)
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Indiana University Bloomington
Schools of Arts and Sciences
United States
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Raff, R A; Sly, B J (2000) Modularity and dissociation in the evolution of gene expression territories in development. Evol Dev 2:102-13
Haag, E S; Sly, B J; Andrews, M E et al. (1999) Apextrin, a novel extracellular protein associated with larval ectoderm evolution in Heliocidaris erythrogramma. Dev Biol 211:77-87
Haag, E S; Raff, R A (1998) Isolation and characterization of three mRNAs enriched in embryos of the direct-developing sea urchin Heliocidaris erythrogramma: evolution of larval ectoderm. Dev Genes Evol 208:188-204
Ferkowicz, M J; Stander, M C; Raff, R A (1998) Phylogenetic relationships and developmental expression of three sea urchin Wnt genes. Mol Biol Evol 15:809-19
Kissinger, J C; Raff, R A (1998) Evolutionary changes in sites and timing of actin gene expression in embryos of the direct- and indirect-developing sea urchins, Heliocidaris erythrogramma and H. tuberculata. Dev Genes Evol 208:82-93
Kissinger, J C; Hahn, J H; Raff, R A (1997) Rapid evolution in a conserved gene family. Evolution of the actin gene family in the sea urchin genus Heliocidaris and related genera. Mol Biol Evol 14:654-65
Klueg, K M; Harkey, M A; Raff, R A (1997) Mechanisms of evolutionary changes in timing, spatial expression, and mRNA processing in the msp130 gene in a direct-developing sea urchin, Heliocidaris erythrogramma. Dev Biol 182:121-33
Bolker, J A; Raff, R A (1996) Developmental genetics and traditional homology. Bioessays 18:489-94
Harkey, M A; Klueg, K; Sheppard, P et al. (1995) Structure, expression, and extracellular targeting of PM27, a skeletal protein associated specifically with growth of the sea urchin larval spicule. Dev Biol 168:549-66
Bisgrove, B W; Andrews, M E; Raff, R A (1995) Evolution of the fibropellin gene family and patterns of fibropellin gene expression in sea urchin phylogeny. J Mol Evol 41:34-45

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