Oscillations are common in biology, e.g. the circadian clock, cardiac pacemaker, cortical rhythms, and have been observed in cell signaling networks as a result of feedback loops. These cellular and physiological oscilla tions maintain homeostasis and analysis of these rhythms is an emerging area in biomedical science. During vertebrate segmentation, ultradian oscillations govern the formation of somites, the segmented anlagen of the vertebral column. In zebrafish, mice and humans, somitogenesis requires Notch signaling, perturbation of which leads to malformed vertebrae, a birth defect called spondylocostal dysostosis. The Notchdependent oscilla tions cause cells in the segmenting tissue of the zebrafish to undergo repeated cycles of expression and repression of Notch target genes. The her (hairy/enhancer of split related tranSCfiptional repressors) genes are thought to form a negative feedback loop within the zebrafish segmentation clock. Current data suggest thai the different /lergenes have both unique and redundant functions.
Aim I is to understand the functional diversification of her genes within the zebrafish clock and to identify cis sequences that govern transcriptional oscillations. To achieve these aims, we will use electrophoretic mobility shift assays (EMSA), immunoprecipitation and transgenic zebrafish.
Aim II is to develop a temperature-sensitive control of the transgenes in order to precisely tune the level and timing of expression. This strategy deals with the general problem of discerning signal integration and gene function within the context of dynamic signaling networks and developmental lime. We are Aim III is to characterize the relationship between cell movement and the segmentation clock. Using timelapse imaging and celt tracking, we will determine the velocity. direction and neighbor relationships of celts in different rQ9ions of the tail bud.

Public Health Relevance

Aberrant somitogenesis leads to birth defects in humans. Later in life abnormal Notch, Wnt or Fgf signaling causes malignancies such as colon cancer and leukemia. We use zebrafish as a tractable, relatively inexpensive vertebrate model system to study how perturbation of these cell signaling pathways affects complex cell behavior in vivo. We believe that better comprehension will lead to more efficacious therapies.

National Institute of Health (NIH)
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Research Project (R01)
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Development - 2 Study Section (DEV2)
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Javois, Lorette Claire
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Yale University
Schools of Arts and Sciences
New Haven
United States
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Schwendinger-Schreck, Jamie; Kang, Yuan; Holley, Scott A (2014) Modeling the zebrafish segmentation clock's gene regulatory network constrained by expression data suggests evolutionary transitions between oscillating and nonoscillating transcription. Genetics 197:725-38
Dray, Nicolas; Lawton, Andrew; Nandi, Amitabha et al. (2013) Cell-fibronectin interactions propel vertebrate trunk elongation via tissue mechanics. Curr Biol 23:1335-41
Lawton, Andrew K; Nandi, Amitabha; Stulberg, Michael J et al. (2013) Regulated tissue fluidity steers zebrafish body elongation. Development 140:573-82
Trofka, Anna; Schwendinger-Schreck, Jamie; Brend, Tim et al. (2012) The Her7 node modulates the network topology of the zebrafish segmentation clock via sequestration of the Hes6 hub. Development 139:940-7
Stulberg, Michael J; Lin, Aiping; Zhao, Hongyu et al. (2012) Crosstalk between Fgf and Wnt signaling in the zebrafish tailbud. Dev Biol 369:298-307
Brend, Tim; Holley, Scott A (2009) Expression of the oscillating gene her1 is directly regulated by Hairy/Enhancer of Split, T-box, and Suppressor of Hairless proteins in the zebrafish segmentation clock. Dev Dyn 238:2745-59
Zhang, Lixia; Kendrick, Christina; Julich, Dorthe et al. (2008) Cell cycle progression is required for zebrafish somite morphogenesis but not segmentation clock function. Development 135:2065-70
Mara, Andrew; Schroeder, Joshua; Holley, Scott A (2008) Two deltaC splice-variants have distinct signaling abilities during somitogenesis and midline patterning. Dev Biol 318:126-32
Mara, Andrew; Schroeder, Joshua; Chalouni, Cecile et al. (2007) Priming, initiation and synchronization of the segmentation clock by deltaD and deltaC. Nat Cell Biol 9:523-30
Holley, Scott A (2007) The genetics and embryology of zebrafish metamerism. Dev Dyn 236:1422-49

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