Gene Activity Study of Japanese Eel During Larval Metamorphosis

Jim Crocker
12th June, 2024

Gene Activity Study of Japanese Eel During Larval Metamorphosis

Image Source: Natural Science News, 2024

Key Findings

  • The study by the Japan Fisheries Research and Education Agency focused on the metamorphosis of Japanese eels
  • Thyroid hormones are crucial for driving the metamorphosis of Japanese eels, similar to other fish species
  • Significant changes in gene expression related to retinoic acid signaling and phototransduction pathways were observed during eel metamorphosis
Understanding the metamorphosis of anguillid eels, particularly the transition from leptocephalus larvae to juvenile glass eels, has long been a challenge due to the difficulty in capturing these metamorphosing larvae in the open ocean. Recent advancements in rearing techniques by the Japan Fisheries Research and Education Agency have now made it feasible to study this critical developmental stage. In a new study, researchers employed RNA sequencing to investigate the dynamics of gene expression during the metamorphosis of Japanese eel leptocephali[1]. Anguillid eels have a unique larval form known as leptocephalus, characterized by a leaf-like, transparent body. The transition from this form to the juvenile glass eel involves significant morphological and physiological changes. This study aimed to uncover the genetic mechanisms underlying these transformations by analyzing the gene expression profiles throughout the metamorphic process. The researchers discovered that thyroid hormones (THs) play a crucial role in driving the metamorphosis of Japanese eels, consistent with findings in other teleost fish. For instance, earlier studies have shown that THs regulate metamorphosis in flounder larvae, with thyroxine (T4) and triiodothyronine (T3) being critical for the process[2]. In flounders, T3 was found to be more potent than T4 in inducing metamorphosis, highlighting the importance of TH concentration and its potent biological effects[2]. This parallels the current study’s findings, where THs were also integral to the metamorphic transition in eels. Additionally, the study revealed that the genetic program initiated by THs during eel metamorphosis involves a series of organismal and cell-specific responses. This stepwise genetic program directs the long-term changes that define the post-metamorphic identity and physiology of the eels. Such findings align with research on flatfish, where THs were shown to orchestrate a complex genetic network leading to asymmetric craniofacial development and eye migration[3]. The conserved role of THs across different species underscores their fundamental role in vertebrate development. Moreover, the study identified significant changes in the expression of genes related to retinoic acid signaling and phototransduction pathways during eel metamorphosis. These pathways have been implicated in the development of asymmetry in flatfish, where retinoic acid is critical for establishing asymmetric pigmentation and modulating eye migration through its interaction with THs[4]. The unexpected expression of visual opsins in the skin of flatfish, which translates illumination differences into retinoic acid gradients, further supports the idea that these pathways are crucial for generating body asymmetry[4]. By leveraging RNA sequencing, the researchers were able to capture the dynamic changes in gene expression during eel metamorphosis, providing a comprehensive view of the genetic underpinnings of this complex process. This study not only advances our understanding of eel development but also offers insights into the broader mechanisms that control body shape and metamorphosis in vertebrates. In conclusion, the Japan Fisheries Research and Education Agency’s study on Japanese eel metamorphosis has elucidated the critical roles of thyroid hormones, retinoic acid signaling, and phototransduction pathways in this process. These findings build upon previous research on flatfish and other teleosts, highlighting the conserved and fundamental nature of these pathways in vertebrate development. As we continue to uncover the genetic basis of metamorphosis, such research will undoubtedly contribute to our broader understanding of developmental biology and evolution.

GeneticsAnimal ScienceMarine Biology

References

Main Study

1) Transcriptome analysis of the Japanese eel (Anguilla japonica) during larval metamorphosis

Published 11th June, 2024

https://doi.org/10.1186/s12864-024-10459-z

Related Studies

2) Effects of various doses of thyroxine and triiodothyronine on the metamorphosis of flounder (Paralichthys olivaceus).

Journal: General and comparative endocrinology, Issue: Vol 67, Issue 3, Sep 1987

3) Sole head transcriptomics reveals a coordinated developmental program during metamorphosis.

https://doi.org/10.1016/j.ygeno.2019.04.011

4) The genome and transcriptome of Japanese flounder provide insights into flatfish asymmetry.

https://doi.org/10.1038/ng.3732


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