Effect of Thyroid Hormone Concentration on the Transcriptional Response Underlying Induced Metamorphosis in the Mexican Axolotl (Ambystoma)

Authors

Robert B. Page, University of KentuckyFollow
Stephen R. Voss, University of KentuckyFollow
Amy K. Samuels, University of Kentucky
Jeramiah J. Smith, University of KentuckyFollow
Srikrishna Putta, University of KentuckyFollow
Christopher K. Beachy, Minot State University

Abstract

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 > or = 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 > or = 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.

Document Type

Article

Publication Date

2-11-2008

Notes/Citation Information

Published in BMC Genomics, v. 9, 78.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Additional files are listed at the end of this page.

Additional file 1:

Analysis of the effect of time in the absence of T₄. Excel table containing statistical and informatic values associated with the analysis of the effect of time in the absence of T₄.

Additional file 2:

Description of the effect of time in the absence of T₄. Word document containing descriptions of the column headers in Additional file 1.

Additional file 3:

DEGs identified by contrasting the T₄ concentrations at each non-zero time point. Excel table containing statistical and informatic values for the DEGs identified by contrasting the 5 and 50 nM T₄ treatments at Days 2, 12, and 28 and imposing fold change criteria.

Additional file 4:

Description of the DEGs identified by contrasting the T₄ concentrations at each non-zero time point. Word document containing descriptions of the column headers in Additional file 3.

Additional file 5:

DEGs identified by the 5 nM regression analysis. Excel table containing statistical and informatic values for the DEGs identified by conducting linear and quadratic regression on the 5 nM dataset and imposing fold change criteria.

Additional file 6:

Description of the DEGs identified by the 5 nM regression analysis. Word document containing descriptions of the column headers in Additional file 5.

Additional file 7:

DEGs identified by the 50 nM regression analysis. Excel table containing statistical and informatic values for the DEGs identified by conducting linear and quadratic regression on the 50 nM dataset and imposing fold change criteria.

Additional file 8:

Description of the DEGs identified by the 50 nM regression analysis. Word document containing descriptions of the column headers in Additional file 7.

Additional file 9:

The 79 genes unique to the 5 nM regression analysis. Excel table containing statistical and informatic values for the 79 DEGs identified by the 5 nM regression analysis and fold change criteria that were not identified by the 50 nM regression analysis.

Additional file 10:

Description of the 79 genes unique to the 5 nM regression analysis. Word document containing descriptions of the column headers found in Additional file 9.

Additional file 11:

The 246 genes unique to the 50 nM regression analysis. Excel table containing statistical and informatic values for the 246 DEGs identified by the 50 nM regression analysis and fold change criteria that were not identified by the 5 nM regression analysis.

Additional file 12:

Description of the 246 genes unique to the 50 nM regression analysis. Word document containing descriptions of the column headers found in Additional file 11.

Additional file 13:

The 111 genes identified as differentially expressed in axolotl epidermis and Xenopus intestine. Excel table containing statistical and informatic values for the genes identified as differentially expressed in axolotl epidermis and Xenopus intestine.

Additional file 14:

Description of the 111 genes identified as differentially expressed in axolotl epidermis and Xenopus intestine. Word document containing descriptions of the column headers in Additional file 13.

Digital Object Identifier (DOI)

http://dx.doi.org/10.1186/1471-2164-9-78

Repository Citation

Page, Robert B.; Voss, Stephen R.; Samuels, Amy K.; Smith, Jeramiah J.; Putta, Srikrishna; and Beachy, Christopher K., "Effect of Thyroid Hormone Concentration on the Transcriptional Response Underlying Induced Metamorphosis in the Mexican Axolotl (Ambystoma)" (2008). Biology Faculty Publications. 18.
https://uknowledge.uky.edu/biology_facpub/18