Sm. Smith et al., DIFFERENTIAL EXPRESSION OF RETINOIC ACID RECEPTOR-BETA ISOFORMS DURING CHICK LIMB ONTOGENY, Developmental dynamics, 202(1), 1995, pp. 54-66
Retinoids influence both morphogenetic events and differentiation duri
ng development of the vertebrate limb. These effects are mediated thro
ugh nuclear retinoid receptors, which modulate target gene expression.
We report here the cloning and characterization of three promoter- an
d splicing-variants of the retinoic acid receptor-beta (RAR-beta) from
chick. These receptor isoforms are independently expressed during lim
b development. RAR beta 2 but not RAR beta 1 transcripts are enriched
three-fold in the posterior limb bud, reflecting the increased RA conc
entrations in this region. RAR beta 1 transcripts are initially presen
t throughout the limb bud mesenchyme and ectoderm, then become restric
ted within perichondrial regions and loose connective tissue of the li
mb. RAR beta 1 expression closely overlaps that of NCAM (neural cell a
dhesion molecule) and tenascin in non-neuronal tissues. RAR beta 2 tra
nscripts are present within a subset of those limb tissues which expre
ss RAR beta 1. In the early limb bud RAR beta 2 transcripts are detect
ed in proximal limb mesenchyme and in the initial mesenchymal condensa
te. In older limbs RAR beta 2 mRNAs are abundant in cells lateral to t
he digit cartilage. Neither RAR beta 1 nor RAR beta 2 transcripts are
associated specifically with regions of limb cell death. The different
ial expression and regulation of RAR beta isoforms suggests these vari
ants may have different roles in limb development. (C) 1995 Wiley-Liss
, Inc.