Expression of steroid receptor coactivator-1 mRNA in the developing mouse embryo: a possible role in olfactory epithelium development

Ligand-dependent nuclear hormone receptors (NRs), such as retinoic acid and thyroid hormone receptors, play critical roles in diverse aspects of devel opment. They enhance or repress transcription by recruiting an array of coa ctivator and corepressor proteins, which function as signaling intermediate s between the NRs and the basal transcriptional machinery. To study the pos sible involvement of these cofactors on tissue-specific regulation of gene expression by NRs, we examined the expression of the coactivator SRC-1 mRNA during mouse embryogenesis by in situ hybridization (ISH). S-35-labeled ri boprobe specific for SRC-I mRNA was used for analysis. The distribution of this transcript was studied from 8.5 to 18.5 embryonic days (E8.5-E18.5) an d in postnatal day 15 (P15). The SRC-1 transcript was largely ubiquitously expressed, even on E8.5. At E14.5 and E18.5, highest levels of SRC-1 transc ript was found in the olfactory epithelium. Significant SRC-1 hybridization signal was also detected in the neocortex, anterior pituitary and heart. W e conclude that (1) SRC-1 mRNA is widely expressed in the developing embryo , and (2) SRC-1 mRNA is expressed at the highest level in the olfactory epi thelium, suggesting that this coactivator may be involved in the developmen t and/or function of the olfactory system.