Changes in gravitational force affect gene expression in developing organ systems at different developmental times

Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA.
BMC Developmental Biology (Impact Factor: 2.67). 02/2005; 5:10. DOI: 10.1186/1471-213X-5-10
Source: PubMed

ABSTRACT Little is known about the affect of microgravity on gene expression, particularly in vivo during embryonic development. Using transgenic zebrafish that express the gfp gene under the influence of a beta-actin promoter, we examined the affect of simulated-microgravity on GFP expression in the heart, notochord, eye, somites, and rohon beard neurons. We exposed transgenic zebrafish to simulated-microgravity for different durations at a variety of developmental times in an attempt to determine periods of susceptibility for the different developing organ systems.
The developing heart had a period of maximum susceptibility between 32 and 56 hours after fertilization when there was an approximately 30% increase in gene expression. The notochord, eye, somites, and rohon beard neurons all showed periods of susceptibility occurring between 24 and 72 hours after fertilization. In addition, the notochord showed a second period of susceptibility between 8 and 32 hours after fertilization. Interestingly, all organs appeared to be recovering by 80 hours after fertilization despite continued exposure to simulated-microgravity.
These results support the idea that exposure to microgravity can cause changes in gene expression in a variety of developing organ systems in live embryos and that there are periods of maximum susceptibility to the effects.

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    • "In this long spin, embryos hatch before the end of the spin period and therefore have an opportunity to swim against the direction of water flow in the vessel. Indeed, Shimada et al. [9] similarly conclude (based on gene expression analyses up to 80 hpf) that as zebrafish embryos mature in the bioreactor, they develop mechanisms to adapt to SMG exposure particularly if the exposure period extends beyond 72 hpf, hatching). Furthermore, they show that the developing heart is most susceptible to SMG exposure between 32–56 hpf when the beating heart tube is changing shape and the atrio-ventricular septum begins to form [22]. "
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    ABSTRACT: It is becoming increasingly important to address the long-term effects of exposure to simulated microgravity as the potential for space tourism and life in space become prominent topics amongst the World's governments. There are several studies examining the effects of exposure to simulated microgravity on various developmental systems and in various organisms; however, few examine the effects beyond the juvenile stages. In this study, we expose zebrafish embryos to simulated microgravity starting at key stages associated with cranial neural crest cell migration. We then analyzed the skeletons of adult fish. Gross observations and morphometric analyses show that exposure to simulated microgravity results in stunted growth, reduced ossification and severe distortion of some skeletal elements. Additionally, we investigated the effects on the juvenile skull and body pigmentation. This study determines for the first time the long-term effects of embryonic exposure to simulated microgravity on the developing skull and highlights the importance of studies investigating the effects of altered gravitational forces.
    PLoS ONE 02/2014; 9(2):e89296. DOI:10.1371/journal.pone.0089296 · 3.23 Impact Factor
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    • "Experiments have shown that cellular organisms may alter their internal structures and activities in response to external forces. Specific experimental studies include the myosin-II redistribution in dictyostelium cell when aspirated by micropipette [1], the remodeling of the actin network in monkey kidney fibroblast under a lateral deformation [2], the increases in voltage-gated K + current when an endothelial cell was stretched [3], and the change in β-actin gene expression of heart and notochord of a transgenic zebrafish after exposure to simulated microgravity [4]. These experimental observations suggest that timely application of appropriate external forces may be used as a means to directly manipulate the dynamics of the internal processes of a cellular organism, leading to the ultimate objective of mechano-control of biological systems. "
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    ABSTRACT: Constantly exposed to various forms of mechanical forces inherent in their physical environment (such as gravity, stress induced by fluid flow or cell–cell interactions, etc), cellular organisms sense such forces and convert them into biochemical signals through the processes of mechanosensing and mechanotransduction that eventually lead to biological changes. The effect of external forces on the internal structures and activities in a cellular organism may manifest in changes its physical properties, such as impedance. Studying variation in the impedance of a cellular organism induced by the application of an external mechanical force represents a meaningful endeavor (from a biosystems perspective) in exploring the complex mechanosensing and mechanotransduction mechanisms that govern the behavior of a cellular organism under the influence of external mechanical stimuli. In this paper we describe the development of an explicit force-feedback control system for exerting an indentation force on a cellular organism while simultaneously measuring its impedance. To demonstrate the effectiveness of this force-control system, we have conducted experiments using zebrafish embryos as a test model of a cellular organism. We report experimental results demonstrating that the application of a properly controlled external force leads to a significant change in the impedance of a zebrafish embryo. These results offer support for a plausible explanation that activities of pore canals in the chorion are responsible for the observed change in impedance.
    Journal of Micromechanics and Microengineering 12/2009; 20(2):025003. DOI:10.1088/0960-1317/20/2/025003 · 1.73 Impact Factor
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    • "Each rohon beard neuron has a single axon that projects peripherally to segmentally innervate the tissue that will ultimately be innervated by dorsal root ganglia cells. Our previous data indicated that there was a pronounced increase in ␤-actin: gfp expression in rohon beard neurons exposed to simulated-microgravity between 24 and 72 hr (Shimada et al., 2005). As the dorsal root ganglia develop , the rohon beard neurons degenerate . "
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    ABSTRACT: Circumstantial evidence has suggested that the primary cilium might function as a gravity sensor. Direct evidence of its gravity-sensing function has recently been provided by studies of rohon beard neurons. These neurons showed changes in the variability of gene expression levels that are linked to the cyclic changes in the Earth's gravitational field due to the Sun and Moon. These cyclic changes also cause the tides. Rohon beard neurons, after the primary cilia have been selectively destroyed, no longer show changes in gene expression variability linked to the cyclic changes in Earth's gravitational field. After the neurons regrow their primary cilia, the link between variability in gene expression levels and the Earth's changing gravitational field returns. This suggests two new functions for the primary cilia, detecting the cyclical changes in the Earth's gravitational field and transducing those changes into changes in the variability (stochastic nature) of gene expression.
    Developmental Dynamics 08/2008; 237(8):1955-9. DOI:10.1002/dvdy.21493 · 2.38 Impact Factor
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