ISSN:
0192-253X
Keywords:
3,5,3′-Triiodothyronine
;
thyroxine
;
thyroid hormone β receptor gene
;
Rana catesbeiana
;
Life and Medical Sciences
;
Genetics
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
Notes:
Two types of thyroid hormone receptor (c-erbA) gene have been identified in mammals and in lower species including chickens and the amphibian Xenopus laevis. The two genes are located on different chromosomes and have been named TRα and TRβ We have described previously the cloning of a TRβ cDNA from Rana catesbeiana (RC) tissues (RC15) and we now report the cloning of a TRβ cDNA from this species. The cloning strategy employed utilized the polymerase chain reaction (PCR), with primers based on the sequences of the X. laevis TRβ cDNA (XenTRβ) and an RCTRβ genomic clone, which, by analogy with XenTRβ, contains some of the 3′ end of the open reading frame together with 3′-untranslated sequences. At the nucleotide and amino acid levels, respectively, the cloned RCTRβ cDNA is 90% and 98% homologous with XenTRβ, and 72% and 76% homologous with RC15. Following in vitro transcription and translation, the cDNA was shown to encode a 48 kilodalton protein which binds 3,5, 3′-triiodothyronine (T3) with high affinity (mean Kd: 0.032 nM). Samples of total or poly(A)+RNA from tadpoles at different stages of metamorphosis and from adult frogs were analyzed for the presence ofTRβ-specific transcripts by slot blot analysis using as probe a 258 bp section of the RCTRβ cDNA. This section of the cDNA does not hybridize to the corresponding section of RC15. In confirmation of previous findings, β-specific transcripts were not detected in RNA from tadpole red blood cells (RBCs) and none was found in RBCs from adult frogs. However, β-specific transcripts were detected in RNA from tail, skin, and liver of stage XIII tadpoles, and the levels were greatly increased in these tissues during metamorphic climax. In the adult frog, the level was minimal in all tissues studied. In other studies using stage XII tadpoles and a reverse transcription-polymerase chain reaction assay, β-specific transcripts were readily detected in tail, skin, kidney, leg, heart, intestine, and eye but minimal or absent in liver, brain, and RBCs. Within 2 days of injection of T3, the level of β-specific transcripts was markedly increased in all tissues. These findings strongly suggest that the expression of the RCTRβ gene is regulated developmentally and/or by thyroid hormone in most tissues of the RC tadpole. © 1994 Wiley-Liss, Inc.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/dvg.1020150405
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