We propose to use the sea squirt, Ciona intestinalis, as a simple chordate model to study key vertebrate developmental processes. Ciona embryos and larvae resemble simplified vertebrate tadpoles with a prominent notochord, dorsal hollow neural tube, and centralized brain. Recent molecular phylogenetic studies indicate that Tunicates (Urochordates) such as Ciona are the closest living relatives of the vertebrates. Ciona possesses a number of exceptional features for elucidating vertebrate developmental processes. The genome is small (~16,000 genes and 160 Mb) and lacks the whole-genome duplication events that bedevil functional genetic analyses in vertebrates. The tadpole is composed of only ~2,000 cells that arise from simple and well-defined lineages, comparable to those seen in C. elegans. It is possible to transform thousands of synchronously developing embryos with desired transgenic DNAs via electroporation. Simply put, the gene networks underlying key vertebrate developmental processes, such as specification of neural crest, are highly conserved in Ciona but not in C. elegans, Drosophila or other invertebrate model systems. The Gans and Northcutt """"""""new head"""""""" theory proposed that most tissues of the vertebrate head represent novel innovations with no homologous counterparts in invertebrates. In vertebrates, these tissues arise from cranial neural crest and placodes, derived from the boundary between the neural tube and anterior neural plate. The focus of this revised proposal is the specification of the Ciona rudimentary cranial placodes and neural crest at the anterior border of the neural tube. We will use a combination of cell- specific labeling methods, cis-regulatory analysis, targeted misexpression assays, gene disruption methods, cell sorting techniques and computational modeling to delineate gene regulatory networks controlling these processes. The research plan includes the following three specific aims: (1) to determine gene regulatory networks governing the specification and invagination of the stomodeum and associated placodes;(2) to determine the gene networks regulating the specification of the putative pituitary;and (3) to characterize the specification of the pigmented otolith and ocellus, and identify Twist target genes responsible for the directed migration of mesenchyme and """"""""synthetic"""""""" ectomesenchyme.

Public Health Relevance

Most of the tissues of the vertebrate head, such as the cranium and face, are believed to represent completely novel innovations with no homologous counterparts in invertebrates. The purpose of this study is to employ the advantages of the primitive chordate Ciona intestinalis as a model system to study the earliest events in their specification and morphogenesis. We are confident that the information that is obtained will illuminate comparable processes in vertebrates.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
1R01NS076542-01A1
Application #
8438221
Study Section
Development - 2 Study Section (DEV2)
Program Officer
Riddle, Robert D
Project Start
2012-09-01
Project End
2017-04-30
Budget Start
2012-09-01
Budget End
2013-04-30
Support Year
1
Fiscal Year
2012
Total Cost
$325,734
Indirect Cost
$106,984
Name
University of California Berkeley
Department
Biochemistry
Type
Schools of Arts and Sciences
DUNS #
124726725
City
Berkeley
State
CA
Country
United States
Zip Code
94704
Farley, Emma K; Olson, Katrina M; Zhang, Wei et al. (2016) Syntax compensates for poor binding sites to encode tissue specificity of developmental enhancers. Proc Natl Acad Sci U S A 113:6508-13
Farley, Emma K; Olson, Katrina M; Zhang, Wei et al. (2015) Suboptimization of developmental enhancers. Science 350:325-8
Diogo, Rui; Kelly, Robert G; Christiaen, Lionel et al. (2015) A new heart for a new head in vertebrate cardiopharyngeal evolution. Nature 520:466-73
Gainous, T Blair; Wagner, Eileen; Levine, Michael (2015) Diverse ETS transcription factors mediate FGF signaling in the Ciona anterior neural plate. Dev Biol 399:218-25
Abitua, Philip Barron; Gainous, T Blair; Kaczmarczyk, Angela N et al. (2015) The pre-vertebrate origins of neurogenic placodes. Nature 524:462-5
Farley, Emma K; Olson, Katrina M; Levine, Michael S (2015) Regulatory Principles Governing Tissue Specificity of Developmental Enhancers. Cold Spring Harb Symp Quant Biol 80:27-32
Wagner, Eileen; Stolfi, Alberto; Gi Choi, Yoon et al. (2014) Islet is a key determinant of ascidian palp morphogenesis. Development 141:3084-92
Levine, Michael (2014) The contraction of time and space in remote chromosomal interactions. Cell 158:243-4
Haupaix, Nicolas; Abitua, Philip B; Sirour, Cathy et al. (2014) Ephrin-mediated restriction of ERK1/2 activity delimits the number of pigment cells in the Ciona CNS. Dev Biol 394:170-80
Wagner, Eileen; Levine, Michael (2012) FGF signaling establishes the anterior border of the Ciona neural tube. Development 139:2351-9

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