of nutritional studies. Vitamin A (retinol) and its derivatives, collectively referred to as retinoids, exert a wide variety of effects on vertebrate development, cellular differentiation and homeostasis (Bollag, 1996). Retinoids, and most notably retinoic acids (RAs) have been of special interest to developmental biologists because of their teratogenic effects on fetal development. Either excess or deficieney of retinoids during pregnaney has been shown to lead to many birth defects (Wilson, 1953; Kochhar. 1967). Thus, normal development seems to require a careful balance of retinoids. How such structurally simpte molecules as the retinoids can have such pleiotropie effects has been a long standing question. In recent years it has become clear that the mechanisms through which RA affects cellular differentiation and embryonie development involve complex interactions between the products of two distinct gene families. The first family consists of a number of nuclear receptors for retinoic acid, and belongs to the superfamily of steroidlthyroid honnone receptors. lt comprises two groups of RA receptors, the RARs (a,B,y), which bind both all-trans RA and 9-cis RA, and the RXRs (a,B,y), which have 9-cis RA as their specitïc ligand. These receptors fonn heterodimeric complexes and act as ligand controlled transcription factors. The nuelear receptor heterodimers regulate gene transcription through binding to specit1c DNA sequences, tenned RA response elements (RARE), found in the promoter regions of target genes.

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F.G. Grosveld (Frank)
Erasmus University Rotterdam
Netherlands Heart Foundation
Erasmus MC: University Medical Center Rotterdam

Kleinjan, D.A. (1998, February 18). Regulation of the Gene for Cellular Retinoic and Acid Binding Protein Type I (CRABP-J). Erasmus University Rotterdam. Retrieved from http://hdl.handle.net/1765/17196