Duplicated leptin receptors in two species of eel bring new insights into the evolution of the leptin system in vertebrates

PLoS One. 2015 May 6;10(5):e0126008. doi: 10.1371/journal.pone.0126008. eCollection 2015.


Since its discovery in mammals as a key-hormone in reproduction and metabolism, leptin has been identified in an increasing number of tetrapods and teleosts. Tetrapods possess only one leptin gene, while most teleosts possess two leptin genes, as a result of the teleost third whole genome duplication event (3R). Leptin acts through a specific receptor (LEPR). In the European and Japanese eels, we identified two leptin genes, and for the first time in vertebrates, two LEPR genes. Synteny analyses indicated that eel LEPRa and LEPRb result from teleost 3R. LEPRb seems to have been lost in the teleost lineage shortly after the elopomorph divergence. Quantitative PCRs revealed a wide distribution of leptins and LEPRs in the European eel, including tissues involved in metabolism and reproduction. Noticeably, leptin1 was expressed in fat tissue, while leptin2 in the liver, reflecting subfunctionalization. Four-month fasting had no impact on the expression of leptins and LEPRs in control European eels. This might be related to the remarkable adaptation of silver eel metabolism to long-term fasting throughout the reproductive oceanic migration. In contrast, sexual maturation induced differential increases in the expression of leptins and LEPRs in the BPG-liver axis. Leptin2 was strikingly upregulated in the liver, the central organ of the reproductive metabolic challenge in teleosts. LEPRs were differentially regulated during sexual maturation, which may have contributed to the conservation of the duplicated LEPRs in this species. This suggests an ancient and positive role of the leptin system in the vertebrate reproductive function. This study brings new insights on the evolutionary history of the leptin system in vertebrates. Among extant vertebrates, the eel represents a unique case of duplicated leptins and leptin receptors as a result of 3R.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anguilla / classification
  • Anguilla / genetics*
  • Anguilla / physiology
  • Animals
  • Evolution, Molecular*
  • Female
  • Fishes / genetics
  • Gene Duplication*
  • Leptin / genetics*
  • Male
  • Phylogeny
  • Receptors, Leptin / genetics*
  • Sexual Maturation / genetics
  • Species Specificity
  • Synteny
  • Tissue Distribution


  • Leptin
  • Receptors, Leptin

Grant support

This work was supported by grants from the European Community, 7th Framework Programme, PRO-EEL, number 245257 to AGL, SD, JT, RD, GT and from the National Research Agency, PUBERTEEL, number ANR-08-BLAN-0173 to SD, KR, MM, JP. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.