AUTHOR=Saito Seiji , Kanazawa Utsugi , Tatsumi Ayana , Iida Atsuo , Takemoto Tatsuya , Suzuki Takayuki 

TITLE=Functional analysis of a first hindlimb positioning enhancer via Gdf11 expression

JOURNAL=Frontiers in Cell and Developmental Biology

VOLUME=12

YEAR=2024

URL=https://www.frontiersin.org/journals/cell-and-developmental-biology/articles/10.3389/fcell.2024.1302141

DOI=10.3389/fcell.2024.1302141

ISSN=2296-634X

ABSTRACT=<p>During the early development of tetrapods, including humans, the embryonic body elongates caudally once the anterior-posterior axis is established. During this process, region-specific vertebral morphogenesis occurs, with the determination of limb positioning along the anterior-posterior axis. We previously reported that <italic>Gdf11</italic> functions as an anatomical integration system that determines the positioning of hindlimbs and sacral vertebrae where <italic>Gdf11</italic> is expressed. However, the molecular mechanisms underlying induction of <italic>Gdf11</italic> expression remain unclear. In this study, we searched for non-coding regions near the <italic>Gdf11</italic> locus that were conserved across species to elucidate the regulatory mechanisms of <italic>Gdf11</italic> expression. We identified an enhancer of the <italic>Gdf11</italic> gene in intron 1 and named it highly conserved region (HCR). In HCR knockout mice, the expression level of endogenous <italic>Gdf11</italic> was decreased, and the position of the sacral-hindlimb unit was shifted posteriorly. We also searched for factors upstream of <italic>Gdf11</italic> based on the predicted transcription factor binding sites within the HCR. We found that inhibition of FGF signaling increased endogenous <italic>Gdf11</italic> expression, suggesting that FGF signaling negatively regulates <italic>Gdf11</italic> expression. However, FGF signaling does not regulate HCR activity. Our results suggest that there are species-specific <italic>Gdf11</italic> enhancers other than HCR and that FGF signaling regulates <italic>Gdf11</italic> expression independent of HCR.</p>