Differential expression of retinoic acid receptor‐β isoforms during chick limb ontogeny

Abstract

Retinoids influence both morphogenetic events and differentiation during development of the vertebrate limb. These effects are mediated through nuclear retinoid receptors, which modulate target gene expression. We report here the cloning and characterization of three promoter-and splicing-variants of the retinoic acid receptor-P (RAR-P) from chick. These receptor isoforms are independently expressed during limb development. RARp2 but not RARPl transcripts are enriched three-fold in the posterior limb bud, reflecting the increased RA concentrations in this region. RARPl transcripts are initially present throughout the limb bud mesenchyme and ectoderm, then become restricted within perichondrial regions and loose connective tissue of the limb. RARPl expression closely overlaps that of NCAM (neural cell adhesion molecule) and tenascin in non-neuronal tissues. RARP2 transcripts are present within a subset of those limb tissues which express RARP1. In the early limb bud RARP2 transcripts are detected in proximal limb mesenchyme and in the initial mesenchymal condensate. In older limbs RARP2 mRNAs are abundant in cells lateral to the digit cartilage. Neither RARPl nor RARP2 transcripts are associated specifically with regions of limb cell death. The differential expression and regulation of RARP isoforms suggests these variants may have different roles in limb development.

Hypoxia Regulates Avian Cardiac Arnt and HIF-1α mRNA Expression

“…Using this chicken-specific cDNA fragment as a probe, a 2771 bp cDNA coding for chicken Arnt was cloned from an incubation day 3.5 chick embryo cDNA library (11). This chicken Arnt clone coded for a protein of 806 amino acids, representing avian Arnt1 (Fig.…”

“…In the second PCR amplification a chicken-specific 584 bp cDNA fragment of Arnt was amplified using 200 nM Fp#1 and Rp#2 at 30 cycles of denaturation at 94°C for 30 s, annealing at 50°C for 1 min, and extension at 72°C for 30 s 4 mM MgCl 2 . The fragment was subcloned into pGemT (Promega), and used to screen an incubation day chick embryo cDNA library (11). Plaques were screened until clonal and sequenced using the T7 Sequenase kit, version 2 (Amersham Pharmacia Biotech, Piscataway, NJ).…”

All-trans retinoic acid stimulates and maintains neurite outgrowth in nerve growth factor-supported developing chick embryonic sympathetic neurons

“…Multiple isoforms of RARP have been described in the chick Smith et al, 1995) as well as in mammals, and several of these mammalian receptor mRNAs have been shown to be the subject of retinoid regulation (de ThB et al, 1989;Zelent et al, 1991;Nagpal et al, 1992). The sizes of the two RARP mRNAs (3.1 and 2.6 kb) in sympathetic ganglia in our studies are in agreement with previous reports for RARP mRNAs in whole chick embryo (Smith and Eichele, 1991) and chick face (Rowe et al, 1991a).…”

A Role for Retinoic Acid in Regulating the Regeneration of Deer Antlers

“…Receptors form dimers and act as ligand-dependent transcription factors binding to specific response elements (see Leid et al, 1992;Chambon, 1996 for reviews). These receptors show distinct patterns of expression in the developing mouse and chick, particularly in the limbs (Smith et al, 1995;Mendelsohn et al, 1992;Dollé et al, 1989Dollé et al, , 1994, and these structures are frequently found to be malformed in vitamin A teratogenesis or deficiency. More recently, the generation of transgenic mice (Cash et al, 1997;Lohnes et al, , 1994Lufkin et al, 1993;Yamaguchi et al, 1998) has identified more precisely the roles of these receptors and their agonists during embryonic development.…”