Subsequent projects | Special projects

Start of funding 01.07.2005

Transcriptional Control of the Popeye (Popdc) Gene family

Prof. Dr. Thomas Brand
University of Würzburg
Department of Cell and Development Biology

Dr. Brian L. Black
University of California, San Francisco
Cardiovascular Research Institute


In recent years, cardiac development has received wide attention, and we have gained important understanding of the molecular network of cardiac development. However, many crucial questions, particularly those related to transcriptional networks and congenital anomalies, remain unanswered. This research cooperation will analyse the transcriptional control of the popdc2 gene, a transmembrane protein involved in the formation of cell-cell contacts in cardiac muscle. Popdc2 is part of gene family that has been conserved in sequence and expression pattern throughout vertebrate evolution. Through the generation of transgenic reporter mice, the important elements and the trans-acting transcription factors that govern popdc2 gene expression will be identified. These studies will provide essential information necessary to unravel the molecular networks controlling cardiac development and may provide valuable insight into the mechanisms underlying congenital cardiac anomalies. We expect the generation of several transgenic lines and embryos that will reveal the basic regulation of the popdc2 gene. These studies will also allow a comparison of the mode of regulation of the popdc2 gene with that of popdc1 and popdc3, which all have a very similar profile of tissue-specific gene expression.

Final report:
This project dealt with gene control of a family of transmembrane proteins, which are specifically expressed in cardiac muscle tissue of vertebrates, including man. These genes, referred to as the Popeye family, are probably involved in cell-cell coupling and are strongly expressed in the conduction tissue of the adult heart.

In tissue culture experiments, we obtained evidence that a short piece of noncoding DNA from one of the members of the Popeye family, Popdc2, is sufficient to direct gene expression in cardiac muscle cells. In this project, we have identified transcription factor binding sites using a combination of experimental and bioinformatic approaches. In addition, we have determined that the same DNA fragment is also sufficient to direct robust cardiac muscle-specific expression in transgenic mice. In our transgenic studies, we found that a 1.7 kb DNA fragment was sufficient to drive reporter gene expression in the heart in a pattern that was indistinguishable from the endogenous Popdc2 gene. Deletional analyses of the Popdc2 regulatory element defined an even smaller 450 bp DNA fragment that was sufficient for expression in the heart. However, expression directed by this smaller element was much weaker when compared to the longer fragment, suggesting a role for transcriptional control mediated through two discrete regulatory regions. To address this possibility, several additional constructs are in preparation. Based on the outcome of these experiments, we will publish the experimental data in the near future.

Along with project-specific work, this cooperation also led to plans for a long-term collaboration. During the funding period, each of the principal investigators on the project visited the other's laboratory twice to facilitate the long-term collaboration. As part of each of the visits, the principal investigators presented lectures about current scientific projects to a wide scientific audience to share ideas broadly and to promote additional collaborative efforts.