CHARACTERIZATION OF CDNAS ENCODING THE CHICK RETINOIC ACID RECEPTOR GAMMA-2 AND PREFERENTIAL DISTRIBUTION OF RETINOIC ACID RECEPTOR-GAMMA TRANSCRIPTS DURING CHICK SKIN DEVELOPMENT

Retinoic acid receptors alpha, beta and gamma (RAR alpha, beta and gam ma) are ligand-inductible transcriptional activators which belong to t he steroid/thyroid hormone receptor superfamily, At least two major is oforms (I and 2) of each RAR arise by differential use of two promoter s and alternative splicing. In mouse, the three RAR genes are expresse d in stage- and tissue-specific patterns during embryonic development, In order to understand the role of the different RARs in chick, RAR g amma 2 cDNAs were isolated from an 8.5-day (stage 35 of Hamburger and Hamilton) chick embryo skin library. The deduced chick RAR gamma S ami no acid sequence displays uncommon features such as 21 specific amino acid replacements, 12 of them being clustered in the amino-terminal re gion (domains A2 and B), and a truncated acidic carboxy-terminal regio n (F domain). However, the pattern of RAR gamma expression in chick em bryo resembles that reported in mouse, particularly in skin where RAR gamma expression occurs in both the dermal and epidermal layers at the beginning of feather formation, and is subsequently restricted to the differentiating epidermal cells, Northern blot analysis suggests that different RAR gamma isoforms could be successively required during ch ick development. (C) 1994 Wiley-Liss, Inc.