Induced metamorphosis: Rectification of a genetic disability by thyroid hormone in the Mexican axolotl Siredon mexicanum

Prahlad, K. V.

doi:10.1016/0016-6480(68)90103-2

Cited by 28 publications

(4 citation statements)

References 15 publications

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“…Several studies with facultative neotenes (Iturriza 1971;Norris and Platt 1973;Prahlad 1968) have demonstrated very low thyroid activities for mature neotenes, but these studies did not investigate possible changes in thyroid activity throughout early development. Larvae of 4.5 cm SVL exhibit a low thyroid activity similar to radioiodide values observed for larvae treated with a thyroid inhibitor.…”

Section: Discussionmentioning

confidence: 99%

Changes in thyroid activity of Ambystoma gracile (Baird) during different larval, transforming, and postmetamorphic phases

Eagleson¹,

McKeown²

1978

Can. J. Zool.

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Thyroid activity for two populations of Ambystoma gracile acclimated to laboratory conditions was assessed by thyroid radioiodide (125I) uptake and serum thyroxine level determined by radioimmunoassay. Both populations exhibited a gradual rise in thyroid activity preceding the mean size for metamorphosis. Larval and transformed salamanders also exhibited a decline in thyroid activity following attainment of this mean size, and this decline was observed for both transformed and neotenous animals. Thyroid activity and serum thyroxine levels were greatest during metamorphic climax. Neoteny was attributed to the generally lower thyroid activity preceding the mean size for metamorphosis which was observed for the high altitude population (having greater neotenic tendencies).

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Section: Discussionmentioning

confidence: 99%

Changes in thyroid activity of Ambystoma gracile (Baird) during different larval, transforming, and postmetamorphic phases

Eagleson¹,

McKeown²

1978

Can. J. Zool.

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“…Thyroid hormone (TH) control of metamorphosis is broadly conserved across amphibians, and radioimmunoassay (RIA) data from anurans (frogs; e.g., Leloup and Buscaglia, 1977) and urodeles (salamanders; e.g., Larras-Regard et al, 1981; Alberch et al, 1986) support the idea that L-thyroxine (T 4 ; relatively inactive form of TH) and 3,5,3′-triiodothyronine (T 3 ; relatively active form of TH) markedly increase at metamorphic climax. TH (T 3 or T 4 ) is necessary and sufficient to induce metamorphosis in anurans (reviewed by Shi, 2000; Brown and Cai, 2007) and urodeles (Prahlad and DeLanney, 1965; Prahlad 1968; Rose, 1995b,c; Rosenkilde and Ussing, 1996) and its biological effects are mediated by nuclear receptors (thyroid hormone receptors α and β; TR-α and TR-β) that repress or activate transcription in a TH-dependent manner (Safi et al, 2004; Buchholz et al, 2006). However, while these and other general features of amphibian metamorphosis are broadly conserved (see Denver et al, 2002), there is considerable variation in the timing, duration, and remodeling patterns that occur across different taxa (Duellman and Trueb, 1994).…”

Section: Introductionmentioning

confidence: 99%

A model of transcriptional and morphological changes during thyroid hormone-induced metamorphosis of the axolotl

Page

Monaghan

Walker

et al. 2009

General and Comparative Endocrinology

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Anuran (frog) metamorphosis has long-served as a model of how thyroid hormones regulate postembryonic development in vertebrates. However, comparatively little is known about urodele (salamander) metamorphosis. We conducted a detailed time-course study of induced metamorphosis in the Mexican axolotl (Ambystoma mexicanum) that probed metamorphic changes in morphology and gene expression in the skin. Using morphometrics, quantitative PCR, histology, and in situ hybridization we demonstrate that the development of transcriptional markers is fundamental to the resolution of early metamorphic events in axolotls. We then use linear and piecewise linear models to identify a sequence of morphological and transcriptional changes that define larval to adult remodeling events throughout metamorphosis. In addition, we show that transcriptional biomarkers are expressed in specific larval and adult cell populations of the skin and that temporal changes in these biomarkers correlate with tissue remodeling. We compare our results with other studies of natural and induced metamorphosis in urodeles and highlight what appear to be conserved features between urodele and anuran metamorphosis.

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“…In contrast, Mexican axolotls ( A. mexicanum ) do not produce a high titer of TH during larval development and thus do not metamorphose (Prahlad 1968; Galton 1992), a process called paedomorphosis (Gould 1977). As a consequence, sexually mature A. mexicanum retain juvenile traits and complete their life cycles in the aquatic habitat.…”

Section: Introductionmentioning

confidence: 99%

Genomics of a Metamorphic Timing QTL: met1 Maps to a Unique Genomic Position and Regulates Morph and Species-Specific Patterns of Brain Transcription

Page

Boley

Kump

et al. 2013

Genome Biology and Evolution

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Very little is known about genetic factors that regulate life history transitions during ontogeny. Closely related tiger salamanders (Ambystoma species complex) show extreme variation in metamorphic timing, with some species foregoing metamorphosis altogether, an adaptive trait called paedomorphosis. Previous studies identified a major effect quantitative trait locus (met1) for metamorphic timing and expression of paedomorphosis in hybrid crosses between the biphasic Eastern tiger salamander (Ambystoma tigrinum tigrinum) and the paedomorphic Mexican axolotl (Ambystoma mexicanum). We used existing hybrid mapping panels and a newly created hybrid cross to map the met1 genomic region and determine the effect of met1 on larval growth, metamorphic timing, and gene expression in the brain. We show that met1 maps to the position of a urodele-specific chromosome rearrangement on linkage group 2 that uniquely brought functionally associated genes into linkage. Furthermore, we found that more than 200 genes were differentially expressed during larval development as a function of met1 genotype. This list of differentially expressed genes is enriched for proteins that function in the mitochondria, providing evidence of a link between met1, thyroid hormone signaling, and mitochondrial energetics associated with metamorphosis. Finally, we found that met1 significantly affected metamorphic timing in hybrids, but not early larval growth rate. Collectively, our results show that met1 regulates species and morph-specific patterns of brain transcription and life history variation.

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Induced metamorphosis: Rectification of a genetic disability by thyroid hormone in the Mexican axolotl Siredon mexicanum

Cited by 28 publications

References 15 publications

Changes in thyroid activity of Ambystoma gracile (Baird) during different larval, transforming, and postmetamorphic phases

Changes in thyroid activity of Ambystoma gracile (Baird) during different larval, transforming, and postmetamorphic phases

A model of transcriptional and morphological changes during thyroid hormone-induced metamorphosis of the axolotl

Genomics of a Metamorphic Timing QTL: met1 Maps to a Unique Genomic Position and Regulates Morph and Species-Specific Patterns of Brain Transcription

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