Widespread expression of the mRNA encoding a novel vitamin D/thyroxine dual binding protein in the turtle Trachemys scripta

Citation
Dj. Whitworth et al., Widespread expression of the mRNA encoding a novel vitamin D/thyroxine dual binding protein in the turtle Trachemys scripta, GEN C ENDOC, 118(2), 2000, pp. 354-358
Citations number
24
Categorie Soggetti
Endocrinology, Nutrition & Metabolism
Journal title
GENERAL AND COMPARATIVE ENDOCRINOLOGY
ISSN journal
00166480 → ACNP
Volume
118
Issue
2
Year of publication
2000
Pages
354 - 358
Database
ISI
SICI code
0016-6480(200005)118:2<354:WEOTME>2.0.ZU;2-W
Abstract
Vitamin D-binding protein (DBP) is the major transport protein for the vita min D sterols in a variety of mammalian and avian species. The DBP found in the emydid family of turtles is unique in that it exhibits high-affinity b inding of bath vitamin D and thyroxine (D/TBP). Sequence analysis has revea led that the emydid D/TBP is homologous to mammalian DBP and shares no homo logy with mammalian thyroxine-binding globulins. Northern blot analysis was used to examine the spatial profile of D/TBP transcription in the turtle T rachemys scripta. In both adults and hatchlings, two transcripts-the expect ed 1.5-kb full-length transcript and a second 0.8-kb transcript-were presen t in nearly all of the tissues examined. In adults, highest expression of t he 1.5-kb transcript was seen in the kidney, gonad, and spleen, with lower levels in the liver and lung and no transcripts in skeletal muscle. In hatc hlings, the full-length transcript was detected in a variety of tissues at similar levels. Injection of hatchlings with thyroxine increased levels of circulating D/TBP and transcript levels. These data are in marked contrast to observations in mammals in which transcription of DBP is confined predom inantly to the liver. Further, the increase in circulating D/TBP associated with increased thyroidal activity may result from a direct or indirect act ivation of D/TBP transcription by thyroxine. (C) Academic Press.