Zebrafish Muscle Toxicity

Zebrafish Muscle Toxicity

The increasing diversity of chemicals produced by industry has caused concerns regarding the potential hazards of biota and human health. The European Union's REACH and US Food and Drug Administration (FDA) regulation declares that the producers are responsible for risk assessment and management of the chemicals that they produce. A major focus is on chemical safety requiring the evaluation of potential adverse toxicological outcomes and ecotoxicological hazards before selling the chemicals. Zebrafish, a teleost with 70% gene homology to humans, is a compelling model for studying toxicology. The use of zebrafish adults and embryos for toxicity testing provides many advantages. Zebrafish are small, easy to maintain and breed, and produce large numbers of embryos. The zebrafish genome is completely sequenced, and their aqueous environment enables direct exposure to toxicants being studied.

Zebrafish embryos are transparent during early development and skeletal muscle fibers are present before 24 hpf. Because the skeletal muscles in zebrafish comprise approximately 60% of adult body mass, studies on toxic effects on muscles are of high relevance. During embryonic development, skeletal muscle progenitor cells are derived from somites. After a series of cell divisions, most of muscle progenitor cells first differentiate into muscle fibers by cell fusion. Continued differentiation occurs through formation, and assembly of the contractile myofibrils and several progenitor cells remain in fully formed skeletal muscle as a self-renewing population of satellite cells that have crucial roles in muscle repair following injury. Recently, many studies have suggested that toxicants can affect the development and functioning of zebrafish skeletal muscle.

Table 1. Effects of toxicants on the development and functioning of zebrafish skeletal muscle.
(Dubińska-Magiera M, et al. 2016)

Toxicant Examples Effect
Heavy metalsMeHg (methylmercury)Alternations in muscle bioenergetics. COX activity inhibitions leading to a decrease of ATP release in muscle
Skeletal muscle damage
U (uranium)Increase in the permeability of the inner mitochondrial membrane and disturbance in transcriptional regulation of respiratory genes results in a decrease in mitochondrial respiration
Upregulation of the COXI and ATP5F1 genes expression
Disorganization in myofibrils and sarcomeres
Cd (cadmium)Changes in skeletal muscle fibers organization, reflected in disruption of sarcomeric pattern, and glycoprotein composition
Disturbance in mitochondrial function resulting in a reduction in swimming performance
Upregulation of different genes including protooncogenes
Depletion of glycogen reserves in muscles
Affected motoneurons axons
Abnormal morphological features and length of the notochord
ArsenReduction of survival and growth
Organic pollutants-endocrine disruptorsBPA (bisphenol A)Impairment of swimming performance, disturbances in muscle activity and gene expression
PesticidesCPO (chlorpyrifos-oxon)Reduced AChE activity but without alternation in muscle development
CPF (chlorpyrifos)Trunk and axial slow muscle fibers length reduction
Dose dependent effect: from reduction of locomotor activity to complete paralysis of axial muscles
NaM (sodium metam)Distorted notochord and altered expression of mRNA markers for notochord and muscle development
Disturbances in fast muscle development

Our Zebrafish Muscle Toxicity

Creative Biogene has successfully developed an in vivo biosensor system with a quantitative readout for assessment of toxicants' influence on motor function. This transgenic zebrafish line TgBAC (hspb11:GFP) expresses a GFP reporter under the control of regulatory elements of the heat shock protein hspb11, which is up-regulated specifically by chemicals that interfere with motor function. Toxicants causing motility defects trigger reversible and dose-dependent hspb11 transgene expression accompanied by changes in the level of GFP intensity. Besides, multiple transgenic lines appropriate for motor behavior impairments associated with the abnormal development of motor neurons and neuromuscular junctions, caused by different chemicals have been established. The pollutants detected by using a zebrafish model system include heavy metals and organic pollutants such as endocrine disruptor compounds.

Highlights

  • A broad range of features can be assessed and measured during environmental monitoring.
  • A quantitative measure for muscle hyperactivity without time lapse analysis, featuring high signal-to-noise ratio, specificity, and sensitivity.
  • Automated measurements of these fluorescent readouts combined with the measurements of altered behavioral effects will provide a multi-parameter assessment of the toxicological impact of compounds.
  • As all these measurements can be carried out with zebrafish embryos, these assays will contribute to the principle of the 3Rs.

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References

  • Dubińska-Magiera M, et al. Zebrafish: a model for the study of toxicants affecting muscle development and function. International Journal of Molecular Sciences, 2016, 17(11): 1941.
  • Shahid M, et al. Zebrafish biosensor for toxicant induced muscle hyperactivity. Scientific reports, 2016, 6(1): 1-14.
  • Moussa E A, et al. Use of Zebrafish (Danio rerio) Embryos as a Model to Assess Effects of Mercury on Developing Skeletal Muscle: A Morphometric and Immunohistochemical Study. International Journal of Morphology, 2018, 36(3).

For research use only. Not intended for any clinical use.

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