Effect of thyroid hormone concentration on the transcriptional response underlying induced metamorphosis in the Mexican axolotl (Ambystoma)

Robert B. Page, Stephen R. Voss, Amy K. Samuels, Jeramiah J. Smith, Srikrishna Putta, Christopher K. Beachy

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Background: Thyroid hormones (TH) induce gene expression programs that orchestrate amphibian metamorphosis. In contrast to anurans, many salamanders do not undergo metamorphosis in nature. However, they can be induced to undergo metamorphosis via exposure to thyroxine (T4). We induced metamorphosis in juvenile Mexican axolotls (Ambystoma mexicanum) using 5 and 50 nM T4, collected epidermal tissue from the head at four time points (Days 0, 2, 12, 28), and used microarray analysis to quantify mRNA abundances. Results: Individuals reared in the higher T4 concentration initiated morphological and transcriptional changes earlier and completed metamorphosis by Day 28. In contrast, initiation of metamorphosis was delayed in the lower T4 concentration and none of the individuals completed metamorphosis by Day 28. We identified 402 genes that were statistically differentially expressed by ≥ two-fold between T4 treatments at one or more non-Day 0 sampling times. To complement this analysis, we used linear and quadratic regression to identify 542 and 709 genes that were differentially expressed by ≥ two-fold in the 5 and 50 nM T4 treatments, respectively. Conclusion: We found that T4 concentration affected the timing of gene expression and the shape of temporal gene expression profiles. However, essentially all of the identified genes were similarly affected by 5 and 50 nM T4. We discuss genes and biological processes that appear to be common to salamander and anuran metamorphosis, and also highlight clear transcriptional differences. Our results show that gene expression in axolotls is diverse and precise, and that axolotls provide new insights about amphibian metamorphosis.

Original languageEnglish
Article number78
JournalBMC Genomics
StatePublished - Feb 11 2008

Bibliographical note

Funding Information:
Aspects of this project were supported by IBN-0242833 from the National Science Foundation (NSF) CAREER Award program and Grant Number 5-R24-RR016344-06 from the National Center for Research Resources (NCRR), a component of the NIH. Additional support for this research came from NIH Grant Numbers P20RR-016741 and P20RR-16481 from the INBRE Program of NCRR. The content of this study is solely the responsibility of the authors and does not necessarily represent the official views of NCRR or NIH or NSF. We thank Donna Walls and the University of Kentucky Microarray Core Facility for processing the GeneChips associated with this study. Arnold Stromberg provided statistical advice during the preparation of this manuscript.

ASJC Scopus subject areas

  • Biotechnology
  • Genetics


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