http://repub.eur.nl/res/aut/8279/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/17196/ 1998-02-18T00:00:00Z 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. http://repub.eur.nl/res/pub/2552/ 1998-01-01T00:00:00Z Retinoic acid (RA), a derivative of vitamin A, is an important molecule for development and homeostasis of vertebrate organisms. The intracellular retinoic acid binding protein CRABP-I has a high affinity for RA, and is thought to be involved in the mechanism of RA signalling. CRABP-I is well conserved in evolution and shows a specific expression pattern during development, but mice made deficient for the protein by gene targeting appear normal. However, the high degree of homology with CRABP-I from other species indicates that the protein has been subject to strong selective conservation, indicative of an important biological function. In this paper we have compared the conservation in the expression pattern of the mouse, chicken and pufferfish CRABP-I genes to substantiate this argument further. First we cloned and sequenced genes and promoter regions of the CRABP-I genes from chicken and the Japanese pufferfish, Fugu rubripes. Sequence comparison with the mouse gene did not show any large blocks of homology in the promoter regions. Nevertheless, the promoter of the chicken gene directed expression to a subset of the tissues that show expression with the promoter from the mouse gene. The pattern observed with the pufferfish promoter is even more restricted, essentially to rhombomere 4 only, indicating that this region may be functionally the most important for CRABP-I expression in the developing embryo. http://repub.eur.nl/res/pub/2547/ 1997-10-01T00:00:00Z The cellular retinoic acid binding protein type I (CRABP-I) shows a highly specific expression pattern during mouse embryonic development. The tissues that express CRABP-I, i.e. the central nervous system (CNS), neural crest, branchial arches, limb bud and frontonasal mass, coincide with those that are most sensitive to unphysiological retinoic acid (RA) concentrations. We have investigated the transcriptional elements that are responsible for the spatiotemporal regulation of CRABP-I expression in the mouse embryo. We show here that a 16 kb fragment harbours all the elements needed for the correct spatiotemporal expression pattern. Upon further dissection of this fragment we have found that expression in the CNS is driven by elements in the upstream region of the gene, while expression in mesenchymal and neural crest tissue is regulated via element(s) located downstream of exon II of the gene. Two distinct fragments in the upstream region are required for expression in the CNS, as neither of these fragments alone is able to drive correct expression of a reporter gene in transgenic mice. DNAseI footprinting analysis of the two upstream fragments revealed the presence of a number of protected elements. One of these regulatory elements has the hallmarks of an RA response element, suggesting that CRABP-I expression in neural tissue can be directly modulated by RA via the RARs/RXRs.