Biological functions of cardiac connexins in mice

• Applicant: Professor Dr. Klaus Willecke
• Subject Area: Cell Biology
• Term: from 2010 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 181352577

Five connexin proteins are expressed in cardiomyocytes of different areas in the mouse heart. All these proteins contribute to different aspects of cardiac functions during embryonic and adult life. Based on previous work in our group and other laboratories, we want to address the following problems in the proposed project: 1) What function fulfills connexin45 (Cx45) in the adult heart? Since Cx45 deficient mice are embryonic lethal due to cardiovascular malformations and physiological abnormalities, it was not possible yet to study its role in the adult heart. We want to address this question by breeding floxed Cx45 mice with inducible cardiomyocytespecific Cre–recombinase-expressing mice. The resulting progeny will be studied histochemically and physiologically. 2) We have generated connexin40 deficient mice in which the alanine residue at position 96 of Cx40 is replaced by a serine residue. The Cx40A96S mutation had been described in heterozygous human patients to cause idiopathic atrial fibrillation. Our present data show that homozygous Cx40A96S mice exhibit persistent and permanent atrial fibrillation after intracardial stimulation, but also develop high blood pressure. We want to generate conditional Cx40A96S flox mice, in order to distinguish direct effects of the dysfunctioning connexin protein from possible secondary effects of high blood pressure in the genesis of this prolonged atrial fibrillation. 3) We have generated cardiomyocyte directed connexin43D378stop mice which lack the last five amino acid residues of the C-terminus of Cx43 (i.e. the PDZ2 binding motif of the ZO1 protein). Our preliminary data indicate that these mice die one to two days after birth. We want to clarify the essential role of the last five C-terminal amino acid residues for cardiac physiology. 4) Very recently three point mutations in the Cx43 protein have been described that were found in human patients suffering from congenital heart disease. We want to study these point mutated Cx43 proteins in transfected cells and characterize a new transgenic mouse line that expresses the Cx43R153Q mutation located in the third Cx43 transmembrane region likely to affect the channel lining pore.

• DFG Programme: Research Grants