Genes induced during the early developmental stages of the Cane Toad, Bufo (Chaunus) marinus.

CSIRO Entomology, Clunies Ross Street, GPO Box 1700, Canberra, ACT 2601, Australia.
Gene Expression Patterns (Impact Factor: 1.36). 08/2008; 8(6):424-32. DOI: 10.1016/j.gep.2008.04.005
Source: PubMed

ABSTRACT Metamorphosis, a critical stage in the development of toads and frogs, involves rapid levels of morphological change. In the current study, we have used microarray analysis to identify shifts in gene expression between tadpole and toadlet stages of the cane toad, Bufo (Chaunus) marinus. Here, we report on nine genes that show the greatest induction during metamorphosis; the gut-associated gastrokine and trefoil factor, blood components haemoglobins alpha/beta, apolipoprotein and serum albumin, a nasal gene olfactomedin, a lens gene gamma-crystallin, and a novel gene with low homology to frog harderin. We present both temporal and spatial expression patterns of these genes identified in developing and adult cane toads. This study extends our knowledge of the molecular basis of toad metamorphosis, and not only offers insights to the genes induced during the general remodelling that occurs but also reveals possible targets for control and manipulation of amphibian pest species, for example, the cane toad in Australia.

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    ABSTRACT: Numerous studies using laboratory-reared tadpoles have shown the importance of thyroid hormones (TH), thyroid receptors (TR), and deiodinase (Dio) enzymes during anuran metamorphosis. Our study focuses on the analysis of thyroid-related genes in tadpoles of wild Wood Frogs (Lithobates sylvaticus (LeConte, 1825); also known as Rana sylvatica (Cope, 1889)) during metamorphosis. Results showed that, in concordance with laboratory-reared studies, thyroid receptor beta (trb) gene expression profiles presented the most marked changes. At climax and compared with premetamorphic stages, brains, tails, and gonad–mesonephros complex (GMC) tissues increased trb expression levels 5-, 21-, and 41-fold, respec-tively (p < 0.05). In addition, gene expression levels of brain deiodinase type II and III showed opposite trends, where 3-fold decrease and 10-fold increase were, respectively, found. This finding supports the idea that thyroid hormone, as it has been demonstrated in laboratory-reared tadpoles, is also involved in natural metamorphosis in wild tadpoles. Interestingly, and contrary to our predictions, we observed that whole brain corticotropin-releasing factor (crf) and crf receptor 1 (crfr1) gene expression levels significantly decrease through metamorphosis in wild L. sylvaticus tadpoles. Further analyses are re-quired to determine if a role of TH in the timing of anuran gonadal development exists, as well as the importance of cell-specific and tissue-specific expression of crf and crfr1 to metamorphosis. Résumé : De nombreuses études concernant les têtards élevés en laboratoire ont démontré l'importance des hormones thy-roïdiennes (TH), des récepteurs thyroïdiens (TR) et des enzymes déiodinases durant la métamorphose des anoures. Notre étude est axée sur l'analyse des gènes liés à la thyroïde chez les têtards sauvages de la grenouille des bois (Lithobates sylva-ticus (LeConte, 1825); également connue sous le nom de Rana sylvatica (Cope, 1889)) durant la métamorphose. Nos résul-tats indiquent que, comme dans les études sur les têtards élevés en laboratoire, les profils d'expression génique des récepteurs thyroïdiens bêta (trb) présentent les changements les plus marqués. Au climax, les niveaux d'expression des trb dans les cerveaux, les queues et les tissus du complexe gonade–mésonéphros (GMC) étaient 5, 21 et 41 fois supérieurs, res-pectivement (p < 0,05), aux niveaux observés aux stades précédant la métamorphose. En outre, les niveaux d'expression gé-nique des déiodinases de types II et III des cerveaux étaient caractérisés par des tendances opposées, soit une réduction par 3 et une augmentation par 10, respectivement. Ce résultat appuie la notion voulant que, comme cela a été démontré pour les têtards élevés en laboratoire, l'hormone thyroïdienne intervienne également dans la métamorphose naturelle des têtards sau-vages. Fait à noter, et contrairement à nos prédictions, nous avons observé que les niveaux d'expression génique du facteur de libération de la corticotropine (crf) et du récepteur 1 du crf (crfr1) diminuent significativement durant toute la métamor-phose chez les têtards sauvages de L. sylvaticus. D'autres analyses sont nécessaires pour déterminer si les TH jouent un rôle dans la séquence du développement gonadique des anoures, ainsi que l'importance de l'expression spécifique aux cellules et aux tissus du crf et du crfr1 dans la métamorphose. Mots‐clés : amphibiens, métamorphose, axe thyroïdien, têtards, grenouille des bois, Lithobates sylvaticus, profils d'expression génique du développement, Rana sylvatica. [Traduit par la Rédaction]
    Canadian Journal of Zoology 08/2012; DOI:10.1139/Z2012-074 · 1.35 Impact Factor
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    ABSTRACT: A major goal for understanding the role of thyroid hormone (TH) in development has been to identify genes regulated by TH in different tissues during frog metamorphosis. The exquisite dependence of metamorphosis on TH also provides a model to study TH endocrine disruption. To identify such TH-regulated genes and select biomarkers for TH endocrine disruption, global gene expression analyses in tadpoles using microarrays have been done in 21 studies, involving five frog species, seven organs, and four endocrine disrupting chemicals. As expected, each organ has a unique set of genes associated with its tissue-specific metamorphic outcome, and functions ascribed to many of these genes correspond to histological changes induced by TH. Also, the large number of transcription factors identified in microarrays is consistent with the molecular mechanisms of TH action. On the other hand, microarray analysis has also revealed interesting findings not predicted from previous morphological or molecular studies. Furthermore, endocrine disruption studies identified candidate biomarkers for TH disruption, and the mechanisms of action of several endocrine disrupting chemicals have been examined. The microarray studies described here have produced a wealth of data on gene expression that requires further functional studies to elucidate the roles of these genes in development and endocrine disruption.
    Current Topics in Developmental Biology 01/2013; 103:329-64. DOI:10.1016/B978-0-12-385979-2.00012-5 · 4.21 Impact Factor
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