Important cardiac transcription factor genes are accompanied by bidirectional long non-coding RNAs.

BACKGROUND: Heart development is a relatively fragile process in which many transcription factor genes show dose-sensitive characteristics such as haploinsufficiency and lower penetrance. Despite efforts to unravel the genetic mechanism for overcoming the fragility under normal conditions, our understanding still remains in its infancy. Recent studies on the regulatory mechanisms governing gene expression in mammals have revealed that long non-coding RNAs (lncRNAs) are important modulators at the transcriptional and translational levels. Based on the hypothesis that lncRNAs also play important roles in mouse heart development, we attempted to comprehensively identify lncRNAs by comparing the embryonic and adult mouse heart and brain. RESULTS: We have identified spliced lncRNAs that are expressed during development and found that lncRNAs that are expressed in the heart but not in the brain are located close to genes that are important for heart development. Furthermore, we found that many important cardiac transcription factor genes are located in close proximity to lncRNAs. Importantly, many of the lncRNAs are divergently transcribed from the promoter of these genes. Since the lncRNA divergently transcribed from Tbx5 is highly evolutionarily conserved, we focused on and analyzed the transcript. We found that this lncRNA exhibits a different expression pattern than that of Tbx5, and knockdown of this lncRNA leads to embryonic lethality. CONCLUSION: These results suggest that spliced lncRNAs, particularly bidirectional lncRNAs, are essential regulators of mouse heart development, potentially through the regulation of neighboring transcription factor genes.