Hormonal Responses in Amphibian Metamorphosis

Frieden, Earl; Just, John J.

doi:10.1016/b978-0-12-452801-7.50006-7

Cited by 72 publications

(41 citation statements)

References 196 publications

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“…A quantitative analysis of trypsin m R N A in pancreas from different stage tadpoles and frogs (Table 1) expressed on a cellular basis clearly demonstrates the lower a m o u n t of m R N A in frogs compared to that in tadpoles. Cell death accounts for m u c h of the weight decrease in the pancreas at m e t a m o r p h o s i s (Frieden and Just 1970;Dodd and Dodd 1976). Therefore at least two factors influence trypsin m R N A levels: cell death and decreased a m o u n t s of m R N A per cell.…”

Section: Factors Affecting the Reduction Of Trypsin M R N Amentioning

confidence: 99%

Developmental and thyroid hormone-dependent regulation of pancreatic genes in Xenopus laevis.

Shi

Brown²

1990

Genes Dev.

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We have isolated and sequenced a cDNA encoding Xenopus laevis pancreatic trypsin, which has -70% amino acid sequence identity to mammalian trypsinogen. Northern blotting analysis shows that the trypsin gene is activated just before the tadpole starts to feed, reaches peak activity in the swimming tadpole (premetamorphosis), and is then repressed during prometamorphosis, attaining its lowest activity at the climax of metamorphosis. The same gene is then activated again in frogs but to a much lower level. The pattern of the changes in trypsin gene expression is followed by at least two other pancreas-specific genes and marks the remodeling of the pancreas of the animal at metamorphosis. Thyroid hormone, which is the causative agent of metamorphosis, can down-regulate trypsin gene expression prematurely.

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Section: Factors Affecting the Reduction Of Trypsin M R N Amentioning

confidence: 99%

Developmental and thyroid hormone-dependent regulation of pancreatic genes in Xenopus laevis.

Shi

Brown²

1990

Genes Dev.

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“…Because of the significant effect of Lthyroxine (T4) 1 and L-triiodothyronine (T3) on stimulating tissue oxygen consumption, the mitochondria was long thought to be the primary locus of action of the thyroid hormones (2). The observations that the thyroid hormones play an important role in mammalian cell differentiation and growth, (3) and in amphibian metamorphosis (4) support the concept that the diverse biologic effects of these hormones may result from a primary effect on the control of gene expression (5).…”

Section: Introductionmentioning

confidence: 99%

Thyroid Hormone Action IN VITRO CHARACTERIZATION OF SOLUBILIZED NUCLEAR RECEPTORS FROM RAT LIVER AND CULTURED GH1 CELLS

Samuels¹,

Tsai²,

Casanova³

et al. 1974

J. Clin. Invest.

234

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A B S T R A C T We previously reported that putative nuclear receptors for thyroid hormone can be demonstrated by incubation of hormone either with intact GH1 cells, a rat pituitary tumor cell line, or with isolated GH1 cell nuclei and rat liver nuclei in vitro.We characterized further the kinetics of triiodothyronine (T3) and thyroxine (T4) binding and the biochemical properties of the nuclear receptor after extraction to a soluble form with 0.4 M KCI. In vitro binding of [lI]T3 and ['I]T4 with GH1 cell and rat liver nuclear extract was examined at 0C and 370C. Equilibrium was attained within 5 min at 370C and 2 h at 0C.The binding activity from GH1 cells was stable for at least 1 h at 370C and 10 days at -200C. Chromatography on a weak carboxylic acid column and inactivation by trypsin and Pronase, but not by DNase or RNase, suggested that the putative receptor was a nonhistone protein. The estimated equilibrium dissociation constants (Kd) for hormone binding to the solubilized nuclear binding activity was 1.80 x 10-10 M (T3) and 1.20 X 10" M (T4) for GH1 cells and 1.57 X 10`" M (T3) and 2.0 X 10' M (T4) for rat liver. These Kd values for T3 are virtually identical to those which we previously reported with isolated rat liver nuclei and GH1 cell nuclei in vitro.The 10-fold greater affinity for T3 compared to T4 in the nuclear extract is also identical to that observed with intact GH1 cells. In addition, the ['I]T3 and ['I]T4 high-affinity binding in the nuclear extract were inhibited by either nonradioactive T3 or T4, which suggests that the binding activity in nuclear extract was identical for T3 and T4.Dr. Samuels is the recipient of a PHS Research Career Development Award AM 46546.

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“…Thus, T3 is thought to act like a steroid hormone in mammals. In amphibians, it has been shown that T3 interacts with a nuclear receptor in various tissues and that the morphological changes induced by T3 are dependent on changes in RNA and protein synthesis (Frieden and Just 1970;Galton 1983). As yet, however, individual T3-responsive genes of amphibians have not been analyzed directly at the molecular level.…”

mentioning

confidence: 99%

“…Virtually every tissue of the larva responds to the thyroid hormone triiodothyronine (T3) with diverse biochemical and morphological changes. Transplantation experiments have established that each tissue is preprogrammed to respond to T3 in a characteristic fashion (for review, see Frieden and Just 1970). Thus, T3 is responsible for coordinating the multiple metamorphic changes occurring throughout the tadpole.…”

mentioning

confidence: 99%

Thyroid hormone induction of keratin genes: a two-step activation of gene expression during development.

Mathisen¹,

Miller²

1987

Genes Dev.

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To determine the mechanism of action of the thyroid hormone triiodothyronine (T3) during metamorphosis of the amphibian epidermis, we have investigated the developmental activation of the 63-kD keratin genes in the frog Xenopus laevis. These genes code for three closely related keratins that first appear in the larval epidermis and accumulate during metamorphosis to become the most abundant proteins in the adult epidermis. We report here that the 63-kD keratins and their mRNAs first appear at stages 48-52. The level of 63-kD keratin gene expression remains relatively low until stage 56 and then increases dramatically. Quantitative analysis of the concentration of 63-kD keratin mRNA demonstrates low levels until stage 55/56, followed by an increase greater than 300-fold from stage 55/56 to the adult. Each adult cell contains approximately 55,000 molecules of the 63-kD keratin mRNAs. T~ is not required for the initial activation of the 63-kD keratin genes, but highlevel expression is absolutely dependent on T3. High-level expression is prevented by propylthiouracil, which inhibits thyroid hormone synthesis and can be induced precociously both in vivo and in vitro with exogenous T 3 as early as stage 48, but not prior to that time. Thus, the full activation of the 63-kD keratin genes during development requires two regulatory steps, one independent and one dependent on T3.

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Hormonal Responses in Amphibian Metamorphosis

Cited by 72 publications

References 196 publications

Developmental and thyroid hormone-dependent regulation of pancreatic genes in Xenopus laevis.

Developmental and thyroid hormone-dependent regulation of pancreatic genes in Xenopus laevis.

Thyroid Hormone Action IN VITRO CHARACTERIZATION OF SOLUBILIZED NUCLEAR RECEPTORS FROM RAT LIVER AND CULTURED GH1 CELLS

Thyroid hormone induction of keratin genes: a two-step activation of gene expression during development.

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