As observed in other tissues, Rara is expressed rather ubiquitously during heart development, both of its isoforms being detected in the myocardium [Mollard et al., 2000]. The other Rars have more restricted distributions, Rarb1 being present in the conotruncal mesenchyme [Ghyselinck et al., 1998], and Rarb2 throughout the developing myocardium [Mollard et al., 2000]. Rarg transcripts are specifically detected in the endocardial cushion tissue and the developing large vessels at E12.5 [Dolle et al., 1990]. None of the Rxr genes display restricted expression patterns in the cardiovascular system.
